The Global Cryosphere Past Present And Future 1st Edition Roger Barry The Global Cryosphere Past Present And Future 1st Edition Roger Barry The Global Cryosphere Past Present And Future 1st Edition Roger Barry

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3. This is the first textbook to address all the components of the Earth’s cryosphere – all forms
of snow and ice, both terrestrial and marine. It provides a concise but comprehensive sum-
mary of cryospheric processes for courses at upper undergraduate and graduate level in
environmental science, geography, geology, glaciology, hydrology, water resource engin-
eering, and ocean sciences. It also provides a superb up-to-date summary of cryospheric
processes for researchers from a range of sciences.
In recent years, studies have shown that the Earth is undergoing potentially rapid
changes in all cryospheric components, including Arctic sea ice shrinkage, mountain gla-
cier recession, thawing permafrost, diminishing snow cover, and accelerated melting of the
Greenland Ice Sheet. This has significant implications for global climate, hydrology, water
resources, and global sea level. This text provides a comprehensive account of snow cover,
glaciers, ice sheets, lake and river ice, permafrost, sea ice, and icebergs – their past history,
and projected future state.
The book builds on courses taught for many decades by Roger G. Barry in the Department
of Geography at the University of Colorado and by Thian Gan in the Department of Civil
and Environmental Engineering at the University of Alberta.
Whilst there are many existing texts on individual components of the cryosphere, no
•
other textbook provides an account of the whole cryosphere.
Developed from courses taught by the authors for many decades.
•
Key processes are explained and observational methods including remote sensing are
•
discussed.
Includes an extensive bibliography, numerous figures and color plates, and a glossary.
•
Includes thematic boxes on selected topics to broaden the scope.
•
Roger G. Barry is former Director of the World Data Center for Glaciology, a Fellow of
the Cooperative Institute for Research in Environmental Sciences, and a Distinguished
Professor of Geography at the University of Colorado at Boulder. He served as Director
of the National Snow and Ice Data Center from 1981–2008. His teaching and research
has been in climate change, arctic and mountain climates, and snow and ice processes.
He has published 20 textbooks, more than 200 articles and supervised 55 graduate stu-
dents. He was co-Vice Chair of the Climate and Cryosphere Project of the World Climate
Research Programme from 2000–2005. Roger was a Guggenheim Fellow (1982–1983) and
a Fulbright Teaching Fellow (Moscow, 2001). He is a Fellow of the American Geophysical
Union and a Foreign Member of the Russian Academy of Natural Sciences. He is a winner
of the Goldthwait Polar Medal (2006); the Founder’s Medal of the Royal Geographical
Society, London (2007); the F. Matthes award of the Cryospheric Specialty Group of the
The Global Cryosphere
Past, Present, and Future

4. Association of American Geographers (2007); and the Humboldt Prize (2009–2011). He
shared the Nobel Peace Prize with other team members of the Intergovernmental Panel
on Climate Change (2007). He has been a Visiting Professor in Australia (1975), France
(2004), Germany (1994, 2009, 2010), Japan (1983), New Zealand (1986), Russia (2001),
Switzerland (1983, 1990, 1997), and the United Kingdom (1997). He is fluent in French,
German, and Russian.
Thian Yew Gan is a Professor at the University of Alberta, Edmonton, and a fellow of the
American Society of Civil Engineers. His teaching and research have been in snow hydrol-
ogy, remote sensing, hydrologic modeling, hydroclimatology, data analysis, climate change
impact on hydrologic processes, and water resources management and planning. Thian has
supervised 30 graduate students and published over 60 refereed papers in various inter-
national journals of the American Geophysical Union, American Meteorological Society,
Royal Meteorological Society, Elsevier Science, America Society of Civil Engineers, and
others. He has been a Visiting Professor at Ecole Polytechnique Federale de Lausanne
(EPFL) (2010); Visiting Scientist at Cemagraf, France (2009); a CIRES Visiting Fellow at
the National Snow and Ice Data Center (NSIDC) at the University of Colorado at Boulder
(2007, 2008); Guest University Professor at the Technical University of Munich (2006–
2007); Adjunct Professor at Utah State University (1998–2005); Honorary Professor at
Xian University of Technology, China (since 2004); Honorary Professor at Yangtze
University, China (2010–2013); Visiting Professor at Kyoto University and JSPS Fellow,
Japan (1999–2000); Guest Professor at Saga University, Japan (1999); Assistant Professor
at the Asian Institute of Technology of Thailand (1989–1990); and regional hydrologist of
the Indian and Northern Affairs Canada (1992–1993) on snow measurements and mapping
at the Arctic.

5. Praise for this book
‘This is the first comprehensive account of the cryosphere. It encompasses all aspects of
the Earth’s systems influenced by below-freezing temperature. Thus glaciology, perma-
frost, seasonal snow cover, fresh-water and sea ice, and the all-pervading atmosphere, are
interlinked after decades of separate treatment. Roger G. Barry has been a leading expo-
nent of this rationalization that has emerged at a critical time now that climate warming is
impinging on the cryospheric “estate.” He has been ably reinforced by the low-temperature
hydrological engineering expertise of his co-author, Thian Yew Gan. The breadth and depth
of coverage and the outstanding scholarship that has typified Barry’s life-long dedication
here unfolds as the masterpiece of his maturing years. It will long remain the ultimate
reference and teaching source and will strongly enhance the urgent present-day quest for
understanding how our Earth functions and how we may be inadvertently changing it.’
Jack D. Ives, University of California, Davis and Carleton University, Ottawa
‘This is an indispensable reference work on the topic of snow and ice, as it includes both
historical aspects, and the latest developments in this urgent field of research. In this com-
pendium you will find aspects of snow and ice that you may have thought about, but never –
until now – had the scientific background knowledge to fully grasp – a truly enlightening
work!’
Ludwig Braun, Commission for Geodesy and Glaciology,
Bavarian Academy of Sciences and Humanities
‘Barry and Gan, with their encyclopedic knowledge and extensive teaching experience,
have produced an extraordinary text that covers virtually all aspects of Earth’s fragile cryo-
sphere. The authors describe in accurate detail the relevant physical processes and how
each part of the cryosphere has changed over time and is anticipated to change in the future.
There is no better time for such a reference, and it will be highly valued by climatologists,
cryospheric scientists, and students engaging in learning about this important component
of our changing planet.’
Anne Nolin, Oregon State University
‘With the appearance of this book, our community has acquired the most comprehensive
presentation of major aspects of the cryosphere – the world of ice on this planet. No other
single book has so successfully integrated the terrestrial cryosphere (snow, glaciers, frozen
ground, and other fresh water frozen body) and the marine cryosphere (sea ice, ice shelves,
and icebergs) in such an attractively readable manner. Each form of ice is illustrated with
respect to research history, observed phenomenon, processes, modeling, and variability,
including the present time under the climate warming. As an excellent introductory text-
book for all forms of the cryosphere it is well suited for advanced undergraduates and
junior graduate students. The book also offers detailed accounts of the processes that have
not been available to many professionals, such as the in situ visual observations of the for-
mation processes of new ice, frazil, grease, shuga and pancake ice; seasonal development
of the snow cover and melt ponds on sea ice; sub-ice shelf circulation; case presentations
of glacier dammed lake bursts; iceberg statistics along the Russian Arctic coast, just to

6. mention a few. In all chapters, the remote sensing applications and their basic theories
are comprehensively presented. The authors have used excellent photographs for visual
explanation and presented one of the most complete bibliographies in glaciology. Each
phenomenon is accompanied with web-addresses, many of which provide extended infor-
mation not only to bring the readers up-to-date, but also to equip them with quasi-real time
information that has an enormous practical significance. The book is a useful source of
information for researchers in other disciplines, climate modelers, and engineers.’
Atsumu Ohmura, Swiss Federal Institute of Technology
‘This text provides an excellent synoptic perspective of the Earth’s cold regions, and
presents an outstanding introduction to those new to the field. The text should serve as a
key reference for upper-level undergraduate instruction and ancillary summary material for
graduate-level courses.’
Derrick J. Lampkin, Pennsylvania State University

7. The Global Cryosphere
Past, Present, and Future
Roger G. Barry
National Snow and Ice Data Center (NSIDC),
University of Colorado, Boulder, USA
and
Thian Yew Gan
University of Alberta, Canada

8. cambridge university press
Cambridge, New York, Melbourne, Madrid, Cape Town,
Singapore, São Paulo, Delhi, Tokyo, Mexico City
Cambridge University Press
The Edinburgh Building, Cambridge CB2 8RU, UK
Published in the United States of America by Cambridge University Press, New York
www.cambridge.org
Information on this title: www.cambridge.org/9780521769815
© Roger G. Barry and Thian Yew Gan 2011
This publication is in copyright. Subject to statutory exception
and to the provisions of relevant collective licensing agreements,
no reproduction of any part may take place without the written
permission of Cambridge University Press.
First published 2011
Printed in the United Kingdom at the University Press, Cambridge
A catalog record for this publication is available from the British Library
Library of Congress Cataloging in Publication data
Barry, Roger Graham.
The global cryosphere: past, present, and future/Roger G. Barry and Thian Yew Gan.
p. cm.
Includes bibliographical references and index.
ISBN 978-0-521-76981-5 (hardback) – ISBN 978-0-521-15685-1 (pbk.)
1. Cryosphere – History. 2. Cold regions – History. 3. Glaciers – History.
4. Ice sheets – History. I. Gan, Thian-Yew. II. Title.
QC880.4.C79B37 2011
551.31–dc22 2011011262
ISBN 978-0-521-76981-5 Hardback
ISBN 978-0-521-15685-1 Paperback
Cambridge University Press has no responsibility for the persistence or
accuracy of URLs for external or third-party internet websites referred to
in this publication, and does not guarantee that any content on such
websites is, or will remain, accurate or appropriate.

9. vii
Contents
Preface page╇ xi
Ackowledgements xii
1 Introduction 1
1.1â•… Definition and extent 1
1.2â•… The role of the cryosphere in the climate system 4
1.3â•… The organization of cryospheric observations and research 5
1.4â•… Remote sensing of the cryosphere 6
Part I╇ The terrestrial cryosphere 9
2A Snowfall and snow cover 11
2.1 History 11
2.2 Snow formation 12
2.3 Snow cover 14
2.4 Snow cover modeling in land surface schemes of GCMs 22
2.5 Snow interception by the canopy 24
2.6 Sublimation 26
2.7 Snow metamorphism 28
2.8 In situ measurements of snow 30
2.9 Remote sensing of snowpack properties and snow-cover area 33
2.10â•… Snowmelt modeling 45
2.11â•… Recent observed snow cover changes 62
2B Avalanches 72
2.12â•… History 72
2.13â•… Avalanche characteristics 73
2.14â•… Avalanche models 79
2.15â•… Trends in avalanche conditions 83
3 Glaciers and ice caps 85
3.1â•… History 85
3.2â•… Definitions 87
3.3â•… Glacier characteristics 88
3.4â•… Mass balance 97
3.5â•… Remote sensing 99

10. Contents
viii
3.6 Glacier flow and flowlines 102
3.7 Scaling 108
3.8 Glacier modeling 109
3.9 Ice caps 111
3.10â•… Glacier hydrology 114
3.11â•… Changes in glaciers and ice caps 121
╇ 4 Ice sheets 138
4.1 History of exploration 138
4.2 Mass balance 141
4.3 Remote sensing 142
4.4 Mechanisms of ice sheet changes 144
4.5 The Greenland Ice Sheet 145
4.6 Antarctica 152
4.7 Overall ice sheet changes 159
4.8 Ice sheet models 159
4.9 Ice sheet and ice shelf interaction 162
4.10â•… Ice sheet contributions to sea level change 163
╇ 5 Frozen ground and permafrost 165
5.1â•… History 165
5.2â•… Frozen ground definitions and extent 167
5.3â•… Thermal relationships 169
5.4â•… Vertical characteristics of permafrost 172
5.5â•… Remote sensing 176
5.6â•… Ground ice 178
5.7â•… Permafrost models 182
5.8â•… Geomorphological features associated with permafrost 183
5.9â•… Changes in permafrost and soil freezing 185
╇ 6 Freshwater ice 190
6.1â•… History 190
6.2â•… Lake ice 191
6.3â•… Changes in lake ice cover 199
6.4â•… River ice 202
6.5â•… Trends in river ice cover 211
6.6â•… Icings 213
Part II╇ The marine cryosphere 219
╇ 7 Sea ice 221
7.1â•… History 221
7.2â•… Sea ice characteristics 223
7.3â•… Ice drift and ocean circulation 248

11. Contents
ix
7.4â•… Sea ice models 254
7.5â•… Leads, polynyas, and pressure ridges 258
7.6â•… Ice thickness 263
7.7â•… Trends in sea ice extent and thickness 265
╇ 8 Ice shelves and icebergs 276
8.1â•… History 276
8.2â•… Ice shelves 277
8.3â•… Ice streams 283
8.4â•… Conditions beneath ice shelves 284
8.5â•… Ice shelf buttressing 286
8.6â•… Icebergs 286
8.7â•… Ice islands 296
Part III╇ The cryosphere past and future 297
╇ 9 The cryosphere in the past 299
9.1â•… Introduction 299
9.2â•… Snowball Earth and ice-free Cretaceous 300
9.3â•… Phanerozoic glaciations 302
9.4â•… Late Cenozoic polar glaciations 303
9.5â•… The Quaternary 306
9.6â•… The Holocene 314
10 The future cryosphere:€impacts of global warming 318
10.1â•… Introduction 318
10.2â•… General observations 319
10.3â•… Recent cryospheric changes 321
10.4â•… Climate projections 321
10.5â•… Projected changes to Northern Hemisphere snow cover 324
10.6â•… Projected changes in land ice 326
10.7â•… Projected permafrost changes 328
10.8â•… Projected changes in freshwater ice 329
10.9â•… Projected sea ice changes 331
Part IV╇ Applications 333
11 Applications of snow and ice research 335
11.1â•… Snowfall 335
11.2â•… Freezing precipitation 336
11.3â•… Avalanches 337
11.4â•… Ice avalanches 339
11.5â•… Winter sports industry 339
11.6â•… Water resources 340

12. Contents
x
11.7 Hydropower 340
11.8 Snow melt floods 341
11.9 Freshwater ice 342
11.10â•… Ice roads 343
11.11â•… Sea ice 344
11.12â•… Glaciers and ice sheets 345
11.13â•… Icebergs 347
11.14â•… Permafrost and ground ice 347
11.15â•… Seasonal ground freezing 349
Glossary 350
References 358
Index 458
Color plates between pp. 210 and 211

13. xi
This text aims to fill a long-standing gap in the scientific literature. While there are many
texts on individual components of the cryosphere – snow cover, glaciers, ice sheets, lake
and river ice, permafrost, sea ice, and icebergs – there is no comprehensive account. The
text is aimed at upper division undergraduates and beginning graduate students in environ-
mental sciences, geography, geology, glaciology, hydrology, water resources engineering,
and ocean sciences, as well as providing a reference source for scientists in all environmen-
tal science and engineering disciplines.
The text builds on an introductory graduate-level course “Topics in snow and ice”
taught by Roger G. Barry (RGB) at the Geography Department, University of Colorado,
Boulder, over the last thirty years, and on part of a graduate-level course, “Advanced
surface hydrology” taught by Thian Yew Gan (TYG) as a professor of hydrology and
water resources engineering at the Department of Civil/Environmental Engineering,
University of Alberta, Edmonton, for the last seventeen years. The former course in turn
built on RGB’s widening exposure to snow and ice data and literature through the work
of the National Snow and Ice Data Center (NSIDC) from 1981 on. Roger G. Barry’s
earlier field experience at the McGill SubArctic Research Laboratory, Schefferville, PQ,
Canada in 1957–1958, Tanquary Fiord, Ellesmere Island, Arctic Canada in summer 1963
and spring 1964, Baffin Island, Arctic Canada in 1967 and 1970, and participation in a
summer school on the Russian icebreaker Kapitan Dranitsyn in autumn 2005 provided
additional insights, as did leaves at the Alfred Wegener Institute for Polar and Marine
Research in 1994, the Geographical Institute, ETH, Zurich in 1997, and the Laboratoire
de Glaciologie et Géophysique in Grenoble in 2004. Roger G. Barry stepped down from
the Directorship of NSIDC in May 2008 and worked half-time from January 2009–­
December 2010. This phase of the writing was greatly assisted by RGB being a recipient
of a Humboldt Foundation Prize Award in 2009–2011. He spent May–October 2009 and
August–October 2010 as a visitor at the Kommission für Glaziologie of the Bavarian
Academy of Sciences in Munich (BASM), courtesy of its Director, Dr. Ludwig Braun.
Thian Yew Gan began his collaboration with RGB during his visit to NSIDC as a CIRES
(Cooperative Institute of Research in Environmental Science) visiting fellow in 2007,
and worked with RGB on this book at Boulder in 2008 and at BASM in 2009 and 2010.
Between 1992 and 2008, TYG has had field experience conducting snow measurement in
the Canadian high Arctic and in the Canadian Prairies, also monitoring river ice break-up
in the Northwest Territories of Canada, remote sensing of snow, and modeling of snow-
melt in the Canadian Prairies and Swiss Alps.
Roger G. Barry
Thian Y. Gan
Preface

14. xii
Acknowledgements
Thanks are due first and foremost to the Humboldt Foundation of Germany for their award
of a Humboldt Prize Fellowship in 2009–2011 which enabled RGB to work on the book
without other distractions. Roger’s time was spent at the Kommission für Glaziologie of the
Bavarian Academy of Sciences, Munich, and thanks go to its Director Dr. Ludwig Braun
for his hospitality and help; also to research staff Dr. Heidi Escher-Vetter and Dr.€Christoph
Mayer, and to staff members Lusia Soturczak and Dieter Schwartz for their assistance.
Thanks also go to Clark Judy, then NSIDC’s Deputy Director, for drawing my attention to
the Humboldt Fellowship program.
Thanks also to a Cooperative Institute for Research in Environmental Sciences (CIRES)
visiting fellowship that supported TYG΄s 2007 visit, and to the National Science and
Engineering Research Council (NSERC) of Canada, that supported his 2008 visit to the
National Snow and Ice Data Center (NSIDC) at the University of Colorado, Boulder, and
to NSIDC for providing the necessary facilities to conduct research on passive microwave
radiometry of snow and for working on the book.
We are indebted to the following chapter reviewers for their suggestions. Any remaining
errors are our own.
Chris Hiemstra, U.S. Army Corps of Engineers, CRREL, Ft. Wainright, AK (Ch.2A)
Karl Birkekand, U.S.D.A. Forest Service National Avalanche Center, Bozeman, MT
(Ch.€2B)
Jack D. Ives, Carleton University, Ottawa (Ch.3)
Mark F. Meier, INSTAAR, University of Colorado, Boulder (Ch. 3)
Ted Scambos, NSIDC, University of Colorado, Boulder (Ch. 4 and Ch. 8)
Fritz Nelson, University of Delaware (Ch. 5)
Glen Liston, Colorado State University (Ch. 6A)
Spyros Beltaos, National Water Research Institute, Burlington, Ontario (Ch. 6B)
Norbert Untersteiner, University of Washington, Seattle, WA (Ch. 7)
Klaus Heine, Department of Geography, University of Regensburg (Ch. 9)
We also thank Drs. Richard Armstrong, Faye Hicks, Jack Ives, Adina Racoviteanu,
Vladimir Romanovsky, Nikolai Shiklomanor, and Koni Steffen for photographs, NSIDC
student helpers Sam Massom, Yana Duday, and Mike Laxer for illustration assistance; and
we thank Matt Lloyd of Cambridge University Press for his enthusiastic support of the
project.
Our thanks go to the following individuals, societies and organizations for their permis-
sion to reproduce figures from books and journals:
Waleed Abdalati, CIRES, University of Colorado, Boulder:€diagram

15. Acknowledgements
xiii
American Association for the Advancement of Science
Science 289(5485), 2000, p. 1744, Figure
American Geophysical Union (all copyrights held by AGU):
Reviews of Geophysics, 41(4) 2003, 1016, p. 2.20, Figure 22.
Reviews of Geophysics, 42, 2004, RG 1004, Fig.1.
Geophysical Research Letters, 36, 2009, L18502, Figure 2
Geophysical Research Letters, 24, 1997, p. 899, Fig.2.
Geophysical Research Letters, 36, 2009, L18502, Figure 2
Journal of Geophysical Research, 108(C3), 2003, 3083, Figure 8.
Journal of Geophysical Research,107 (C10), 2002, 8044, p. 8 Fig. 9
Journal of Geophysical Research, 98(C6), 1993, p. 1088, Fig. 1
Journal of Geophysical Research, 114:€2009. D04109. pp.9, 10 and 11, Figures 4, 5 and 6
Journal of Geophysical Research, 114(D6):€2009, D06111. p. 10, Figure 5
Water Resources Research 36(9) 2000, p. 2666 Figure 1.
American Meteorological Society:
Meteorology of the Southern Hemisphere, 1998, p. 187 Fig. 4.12.
Bulletin Amer. Met. Soc., 90 (2009), p. 112, Figure 1.
Journal of Climate 12, 1998, p.1826, Figs. 13 and 14.
Proceedings 14th Conference on Climatology, Seattle, WA, January 12–15. Paper 7.12,
Fig. 5.
Applied Physics Laboratory, University of Washington, Seattle,
APL-UW 8510, An introduction to ice in the Polar Oceans. G.A. Maykut, 1985
p. 13, Figure 3b.
A.A. Balkema, Lisse, Netherlands, Taylor Francis Publishers
Zhang, T-J. and 4 others. R. G. Barry was co-author. 2003. Distribution of seasonally and
perennially frozen ground in the Northern Hemisphere. In M. Phillips, S.M. Springman
and L.U. Arenson (eds). Permafrost, Vol. 2, Proceedings of the 8th International
Conference on Permafrost., p. 1291, Fig. 1.
ISBN 9058095827
Cambridge University Press:
M.C. Serreze and R.G. Barry, The Arctic climate system, 2005, 184, Fig 7.3.
IPCC 2007. Climate Change 2007:€The Physical Science Basis, Contribution of Working
Group I, to the Fourth Assessment Report of the Intergovernmental Panel on Climate
Change, Chapter 1, Coordinating editors:€Le Treut, H. Somerville, R. p. 101, Figure 1.3.
IPCC, 2007:€Summary for Policymakers. In:€Climate Change 2007:€The Physical Science
Basis. Contribution of Working Group I to the Fourth Assessment Report of the
Intergovernmental Panel on Climate Change [Solomon, S. and Qin, D. et al., (eds.)],
p.€14, figure SPM5.

16. Acknowledgements
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Climate Change 2007: G.A. Meehl et al. The Physical Science Basis. Contribution of
Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on
Climate Change, Ch. 10, Figs. 10.13b and 10.14 top right panels.
Dr. D. Cline, NOHRSC, National Weather Service, USA: diagram
Danish Meteorological Institute, Copenhagen:
Scientific Report 05-02. Multi-decadal variation of the East Greenland sea-ice extent, AD
1500–2000. K. Lassen and P. Thejll. 2005, p. 6. Fig. 1.2
Elsevier (all copyrights held by Elsevier; reproduced with permission):
Deep-sea Research 29(8A) p. 968, Fig.1, 1982.
Earth and Planetary Science Letters 280 (2009) p.56, Fig. 6.
Global and Planetary Change 69, 2009, p. 60, Table 1.
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Barber, D.G. and Massom, R.A. p.9, Fig. 1.
Environment, Canada, Canadian Ice Service, Ottawa
Egg Code diagram. Image by Canada Ice Service. Reproduced with the kind permission
of the Minister of Public Works and Government Services (2011)
European Geophysical Union (reproduced courtesy of Matthias Braun):
The cryosphere, 3, 2009, p. 47, Figure 4(h).
Matthias.braun@uni-bonn.de
Hokkaido University, Japan: J. Faculty of Science II(4), 1966, pp. 321–55, Plates 1, 2, 7,
8, 9, 10, and 14. (Magono and Lee)
Institute of Arctic and Alpine Research, University of Colorado, Boulder
Occasional Paper # 58, Glaciers and the changing Earth system: a 2004 snapshot.
(M Dyurgerov and M. Meier) p.18 Figure 4; p. 19, Figure. 5b; p. 21, Figure 6.
International Glaciological Society (with kind permission from Glen Liston):
Ann. Glaciol. 21, p. 388, Fig.1.
Molecular Diversity Preservation International (MDPI), Basel, Switzerland. © 2008 by
MDPI
Sensors 8, 2008. p. 3373, Fig. 5.
New Mexico Bureau of Geology and Mineral Resources
P.V. Dickfoss et al., 1997.
In K. Mabery (Compiler) A Natural History of El Malpais., Bulletin 156, p. 97 Fig. 5.
David Robinson, Rutgers University, NJ. graph and diagrams.
Royal Meteorological Society:
Weather 44(10), 1989, p. 407. Fig. 2.

17. Acknowledgements
xv
SAGE Publications (© 2002 by C. J. van der Veen. Reprinted by permission of SAGE):
Progress in Physical Geography 2002, 26, p. 99, Fig. 1
Scott Polar Research Institute, Cambridge, UK:
Polar Record 17 (1975), p. 528, Fig. 6.
Springer (all copyrights by Springer; with kind permission from Springer Science +
Business Media):
Climate Dynamics 34 (2010) p.973 Figs. 2a,b,d,f.
Climate Dynamics 30 (2008) p. 311, Fig.2a, c, e.
F. Svoboda, University of Zurich. Cumberland Peninsula data used by UNEP/GRID.
Swets and Zeitlinger, Lisse
Proceedings 8th
International Conference on Permafrost, Zurich 2003, Vol. 2, p. 1291, Fig. 1.
Swiss Permafrost Monitoring Network (PERMOS), University of Zurich. Temperature
graph.
Taylor Francis Group (http://www.informaworld.com)
Philosophical Magazine, 6(71), 1961. p. 1369, Fig. 7.
UNEP/GRID Arendal, Norway
Sea ice ages in 1988, 1990, 2001 and 2005 in the Arctic Ocean.
http://maps.grida.no/go/graphic/change-in-the-age-of-ice-on-
the-arctic-ocean-comparing-september-ice-ages-in-1988–1990–2001- and-2005.
Cartographer/designer: Hugo Ahlenius, UNEP/GRID-Arendal
The global distribution of the components of the cryosphere. Hugo Ahlenius,
http://upload.wikimedia.org/wikipedia/commons/b/ba/Cryosphere_Fuller_Projection.
png
Glacier shrinkage since the Little Ice Age in the Cumberland Peninsula, Baffin Island.
http://maps.grida.no/go/graphic/glacie r-shrinking-on-cumberland
-peninsula-baffin-island-canadian-arctic
Cartographer/designer Hugo Ahlenius
Water Resource Publications, Highlands Ranch, CO 80163-0026
Petryk in S. Beltaos (Ed), 1995, River ice jams, p. 151, Fig. 5.2.

19. 1
1 Introduction
1.1╇ Definition and extent
The cryosphere is the term which collectively describes the portions of the Earth’s surface
where water is in its frozen state€– snow cover, glaciers, ice sheets and shelves, freshwater
ice, sea ice, icebergs, permafrost, and ground ice. The word kryos is Greek meaning icy
cold. Dobrowolski (1923, p.2; Barry et al. (2011)) introduced the term cryosphere and
this usage was elaborated by Shumskii (1964, pp. 445–55) and by Reinwarth and Stäblein
(1972). Dobrowolski and Shumskii included atmospheric ice, but this has generally been
excluded. The cryosphere is an integral part of the global climate system. It has important
linkages and feedbacks with the atmosphere and hydrosphere that are generated through
its effects on surface energy and on moisture fluxes, by releasing large amounts of fresh-
water when snow or ice melts (which affects thermohaline oceanic circulations), and by
locking up freshwater when they freeze. In other words, the cryosphere affects atmospheric
processes such as clouds and precipitation, and surface hydrology through changes in the
amount of fresh water on lands and oceans. Slaymaker and Kelly (2006) published a study
of the cryosphere in the context of global change, while Bamber and Payne (2004) detailed
the mass balance of glaciers, ice sheets, and sea ice. The discipline of glaciology encom-
passes the scientific study of snow, floating ice, and glaciers, while the study of permafrost
(cryopedology) has largely developed independently.
In a report on the International Polar Year, March 2007–March 2009, the World
Meteorological Organization (2009) identified the following important foci of cryospheric
research:€rapid climate change in the Arctic and in parts of the Antarctic; diminishing snow
and ice worldwide (sea ice, glaciers, ice sheets, snow cover, permafrost); the contribution
of the great ice sheets to sea-level rise and the role of subglacial environments in control-
ling ice-sheet dynamics; and methane release to the atmosphere from melting permafrost.
These topics will be discussed, but in each case we first survey the basic characteristics
and processes at work for each cryospheric element. We also consider the past cryosphere
throughout geological time and model simulations of future cryospheric states and their
significance. In the concluding chapter, practical applications of snow and ice research are
presented. We begin by considering the dimensions of the cryosphere.
Dimensions of the cryosphere
Table 1.1 shows the major characteristics of the components of the cryosphere.
Figure 1.1 illustrates the global distribution of these components.

20. Introduction
2
Table 1.1╇ Areal and volumetric extent of major components of the cryosphere
(updated after Goodison etal., 1999).
Component Area (106
km2
)
Ice volume
(106
km3
)
Sea level
�
equivalent (m)a)
LAND SNOW COVERb)
Northern Hemisphere
Late January
Late August
46.5
3.9
0.002
Southern Hemisphere
Late July
Early May
0.85
0.07
SEA ICE
Northern Hemisphere
Late March
Early September
14.0 c)
6.0 c)
0.05
0.02
Southern Hemisphere
Late September
Late February
15.0 d)
2.0 d)
0.02
0.002
PERMAFROST (underlying the exposed land surface, excluding Antarctica and S. Hemisphere
high mountains)
Continuous e)
Discontinuous and sporadic
10.69
12.10
0.0097–0.0250
0.0017–0.0115
0.024–0.063
0.004–0.028
CONTINENTAL ICE AND ICE
SHELVES
East Antarcticaf)
WestAntarcticaf)
andAntarctic Peninsula
Greenlandg)
10.1
2.3
1.7
21.7
3.0
2.85
52
5
7.3
Small ice caps andh)
mountain glaciers
Ice shelvesf)
0.74
1.5
0.24
0.66
0.6
a)
Sea level equivalent does not equate directly with potential sea-level rise, as a correction is
required for the volume of the Antarctic and Greenland Ice Sheets that are presently below sea
level. 400,000 km3
of ice is equivalent to 1 m of global sea level.
b)
Snow cover includes that on land ice, but excludes snow-covered sea ice (Robinson et al.,
1995).
c)
Actual ice areas, excluding open water. Ice extent ranges between approximately 7.0 and 15.4
× 106
km2
for 1979–2004 (Parkinson et al., 1999a).
d)
Actual ice area excluding open water (Gloersen et al., 1993). Ice extent ranges between
approximately 3.8 and 18.8 × 106
km2
. Southern Hemisphere sea ice is mostly seasonal and
generally much thinner than Arctic sea ice.
e)
Data calculated using the Digital Circum-Arctic Map of Permafrost and Ground-Ice Conditions
(Brown et al., 1998) and the GLOBE-1 km Elevation Data Set (Zhang et al., 1999).
f)
Ice-sheet data include only grounded ice. Floating ice shelves, which do not affect sea level,
are considered separately (Huybrechts et al., 2000; Drewry et al., 1982; Lythe et al., 2001).
g)
Dahl-Jensen et al. (2009).
h)
Radić and Hock (2010).

21. 1.1╇ Definition and extent
3
The cryosphere has seasonally varying components and more permanent features. Snow
cover has the second largest extent of any component of the cryosphere, with a mean annual
area of approximately 26 million km2
(Table 1.1). Almost all of the Earth’s snow-covered
land area is located in the Northern Hemisphere, and temporal variability is dominated
by the seasonal cycle. The Northern Hemisphere mean snow-cover extent ranges from
~ 46 million km2
in January to 3.8 million km2
in August. Sea ice extent in the Southern
Hemisphere varies seasonally by a factor of five, from a minimum of 3–4 million km2
in
February to a maximum of 17–20 million km2
in September (Gloersen et al., 1993). The
seasonal variation is much less in the Northern Hemisphere where the confined nature and
high latitudes of the Arctic Ocean result in a much larger perennial ice cover, and the sur-
rounding land limits the equator-ward extent of wintertime ice. The Northern Hemisphere
ice extent varies by only a factor of two, from a minimum of 7–9 million km2
in September
to a maximum of 14–16 million km2
in March during 1979–2004. Subsequent years have
seen much smaller areas in late summer.
Ice sheets are the greatest potential source of freshwater, holding approximately 77 per-
cent of the global total. Freshwater in ice bodies corresponds to 65 m of world sea level
equivalent, with Antarctica accounting for 90 percent of this and Greenland almost 10 per-
cent. Other ice caps and glaciers account for about 0.5 percent (Table 1.1).
The World Atlas of Snow and Ice Resources (Kotlyakov, 1997) provides maps of cli-
matic factors (air temperature, solid precipitation), snow water equivalent, runoff, glacier
morphology, mass balance and glacier fluctuations, river freeze-up/break-up, avalanche
occurrence, and many other variables. The maps range from global, at a scale 1:60 mil-
lion, to regional maps at 1:5 million to 1:10 million and local maps of individual glaciers
at 1:€25,000 to 1:100,000.
Permafrost (perennially frozen ground) may occur where the mean annual air temperature
(MAAT) is less than€–1°C and is generally continuous where MAAT is less than€–7€°C. It is
Snow
Sea ice
Ice shelves
Ice sheets
Galciers and ice caps
Permafrost,
continuous
Permafrost,
discontinuous
Permafrost,
isolated
Figure 1.1 The global distribution of the components of the cryosphere (from Hugo Ahlenius, courtesy UNEP/GRID-Arendal,
Norway). http://upload.wikimedia.org/wikipedia/commons/b/ba/Cryosphere_Fuller_Projection.png. See color
version in plates section.

22. Introduction
4
estimated that permafrost underlies about 22 million km2
of exposed Northern Hemisphere
land areas (Table 1.1), with maximum areal extent between about 60º and 68ºÂ€N. Its thick-
ness exceeds 600 m along the Arctic coast of northeastern Siberia and Alaska, but perma-
frost thins and becomes horizontally discontinuous towards the margins. Only about
2€million km2
consists of actual ground ice (“ice-rich”). The remainder (dry permafrost) is
simply soil or rock at subfreezing temperatures. A map of Northern Hemisphere permafrost
and ground ice (1:10 million) was published by Brown et al. (2001) and is available elec-
tronically at:€http://nsidc.org/data/ggd318.html
Seasonally frozen ground, not included inTable 1.1, covers a larger expanse of the globe than
snow cover. Its depth and distribution varies as a function of air temperature, snow depth and
vegetation cover, ground moisture, and aspect. Hence it can exhibit high temporal and spatial
variability. The area of seasonally frozen ground in the Northern Hemisphere is approximately
55 million km2
or 58 percent of the land area in the hemisphere (Zhang et al., 2003b).
Ice (see Note 1.1) also forms on rivers and lakes in response to seasonal cooling. The
freeze-up/break-up processes respond to large-scale and local weather factors, producing
considerable inter-annual variability in the dates of appearance and disappearance of the
ice. Long series of lake-ice observations can serve as a climatic indicator; and freeze-up
and break-up trends may provide a convenient integrated and seasonally specific index
of climatic perturbations. The total area of ice-covered lakes and rivers is not accurately
known and hence this element has not been included in Table 1.1.
1.2╇ The role of the cryosphere in the climate system
The elements of the cryosphere play several critical roles in the climate system (Barry,
1987; 2002b). The primary one operates through the ice–albedo feedback mechanism. This
concerns the expansion of snow and ice cover increasing the albedo, thereby increasing
the reflected solar radiation and lowering the temperature, thus enabling the ice and snow
cover to expand further. At the present day this effect is working in the opposite direction
with the shrinkage of snow and ice cover lowering the albedo and increasing the absorp-
tion of solar radiation, thereby raising the temperature and further reducing the snow and
ice cover. On a global scale the ice–albedo effect amplifies climate sensitivity by about
25–40€percent (depending on cloudiness changes).
A second major influence is the insulation of the land surface by snow cover and of the
ocean (as well as lakes and rivers) by floating ice. This insulation greatly modifies the
temperature regime in the underlying land or water. The difference in the temperature of
air overlying bare ground versus snow-covered ground is of the order of 10 °C based on
winter measurements in the Great Plains of North America. The absence of snow cover
could mean higher mean-annual surface air temperature, but severe wintertime cooling,
and a substantial increase in permafrost areas over high latitude regions of the Northern
Hemisphere such as Siberia (Vavrus, 2007).
Athird effect is on the hydrological cycle due to the storage of water in snow cover, glaciers,
ice caps, and ice sheets and associated delays in freshwater runoff. The time scales involved

23. 1.3╇ The organization of cryospheric observations and research
5
range from weeks to months in the case of snow cover, decades to centuries for glaciers and ice
caps, to 105
–106
years in the case of ice sheets and permafrost. The more permanent features of
the cryosphere have accordingly a great influence on eustatic changes in global sea level (see
Table 1.1). A 1 mm rise in eustatic sea level requires the melting of 360 Gt of ice.
A fourth effect is related to the latent heat involved in phase changes of ice/water. This
applies to all elements of the cryosphere. It is estimated, for example, that a 10 cm snow
cover over England has a latent heat of fusion of 1015
kJ; melting the Greenland Ice Sheet
would require ~1021
kJ. Ohmura (1987) calculated that the melting of ice since the Last
Glacial Maximum about 20 ka accounted for 26–39 × 103
MJ m−2
, of similar magnitude to
the total energy stored in the climate system (30–60 × 103
MJ m−2
).
A fifth effect is caused by seasonally frozen ground and permafrost modulating water
and energy fluxes, and the exchange of carbon (especially methane), between the land and
the atmosphere.
1.3╇ The organization of cryospheric observations and research
The organization of cryospheric data began during the International Geophysical Year
(IGY), 1957–1958, with the establishment of the World Data Center (WDC) system.
WorldDataCentersforGlaciologyweredesignatedintheUnitedStates,theSovietUnion,
and the United Kingdom. In 1976, World Data Center-A for Glaciology was �
transferred
from the US Geological Survey in Tacoma, WA to the National Oceanic and Atmospheric
Administration (NOAA) in Boulder, CO, where it has subsequently been �
operated by the
University of Colorado (Barry, 2002a). The scope of its operations expanded€to address
data on all forms of snow and ice and in 1981 the National Environmental Satellite Data
and Information Service (NESDIS) of NOAA designated a National Snow and Ice Data
Center (NSIDC). Its financial support was greatly augmented by contracts and grants from
the NationalAeronautics and Space Agency (NASA) and the National Science Foundation.
Roger G. Barry served as Director from 1976 until 2008 and was succeeded by Mark
Serreze. Details on its data holdings and research activities may be found at:€http://nsidc.
org. World Data Centre-C for Glaciology addresses bibliographic data and is operated by
the Scott Polar Research Institute at Cambridge, UK. World Data Center-D for Glaciology
was established at the Laboratory for Glaciology and Geocryology, Lanzhou, China in
1986. The letter designations were dropped in 1999 and in 2009 the International Council
of Science (ICSU) decided to convert the WDC system into a World Data System. This is
not yet operational but in the interim the WDCs continue to function as before.
Over the last few years, major advances have occurred in the organization of snow and
ice observations and research. Initially, the organization took place within the various cry-
ospheric subfields (snow, avalanches, glaciers and ice sheets, freshwater ice, sea ice, and
permafrost). Then, beginning in the 1990s, the Global Climate Observing System (GCOS),
and its partners the Global Ocean Observing System (GOOS) and Global Terrestrial
Observing System (GTOS), defined Essential Climate Variables (ECVs) (Barry, 1995;
GCOS, 2004). For the cryosphere, these include snow cover, glaciers, permafrost, and sea

24. Introduction
6
ice. Global Terrestrial Networks (GTN) were specified for glaciers (GTN-G) and perma-
frost (GTN-P) (http://gosic.org/ios/GTOS_observing_system.asp).
At a higher level, the Integrated Global Observing System (IGOS) initiated the prepar-
ation of a report on a cryosphere theme (Key et al., 2007) which documented the avail-
able and needed cryospheric data sets. In May 2007, the 15th Congress of the World
Meteorological Organization (WMO) received a proposal from Canada to create a Global
Cryosphere Watch (GCW), analogous to the Global Atmosphere Watch (GAW). The GCW
is now in a planning stage seeking to identify the necessary steps to implement it (http://
igos-cryosphere.org/documents.html).
In July 2007, at the XXIVth General Assembly of the International Union of Geophysics
and Geodetics (IUGG) in Perugia, Italy, the IUGG Council launched the International
Association of Cryospheric Sciences (IACS) as the eighth IUGG Association. This super-
seded the International Commission for Snow and Ice (ICSI) (Radok, 1997, Jones, 2008).
The IACS has the following five divisions:€snow and avalanches; glaciers and ice sheets;
marine and freshwater ice; cryosphere, atmosphere and climate; and planetary and other
ices of the solar system (http://www.iugg.org/associations/iacs.php).
The International Glaciological Society (IGS)€– successor to the British Glaciological
Society originally founded in 1936€– is based in Cambridge, England. It organizes inter-
national conferences on all topics addressed by glaciology and publishes the Journal of
Glaciology and the Annals of Glaciology; the latter contains papers presented at IGS-
sponsored conferences. Other journals include the online-only journal of the European
Geophysical Society, The Cryosphere, Cold Regions Science and Technology, Zeitschrif für
Gletscherkunde und Glaziologie, Seppyo published by the Japanese Society of Snow and
Ice, Sneg i Lyod (snow and ice), a successor to Materialy Glatsiologicheskhikh Issledovanni
(in Russian), published by the RussianAcademy of Sciences, Institute of Geography, and the
Journal of Glaciology and Cryopedology (in Chinese), published by the Lanzhou Institute
of Glaciology. Snow and ice research is, however, published in a wide variety of disciplinary
and interdisciplinary journals, as shown by the references (pp. 358–459).
On the research side, the World Climate Research Programme (WCRP) established a
Climate and Cryosphere (CliC) Project in 2000 (Allison et al., 2001; Barry, 2003) that has
four thematic areas€– interactions between the atmosphere, snow and land, interactions
between land ice and sea level, interactions between sea ice, oceans, and the atmosphere,
and cryosphere–ocean/cryosphere–atmosphere interactions on a global scale (http://clic.
npolar.no). The CliC project is directed by a Science Steering Group and regularly organ-
izes workshops and conferences.
Grassl (1999) presented an overview of international research programs and groups that
have contributed observations or modeling studies of the cryosphere and its elements.
1.4╇ Remote sensing of the cryosphere
Cryospheric science has benefitted enormously from the ready availability of satellite data
since the mid 1960s. We will summarize briefly the main instruments that have operated
and some of their applications. Further details are provided in the relevant chapters.

25. 1.4 Remote sensing of the cryosphere
7
The hemispheric analysis of snow cover extent began in October 1966 from
NOAA’s polar orbiting Very High Resolution Radiometer (VHRR) and continued
with the use of the Advanced VHRR (AVHRR) and other visible-band satellite data.
Global snow cover maps are now available from the Moderate Resolution Imaging
Spectroradiometer (MODIS) on Terra (February 2000–present) and Aqua (July 2002–
present). In December 1972, NASA launched the Electrically Scanning Microwave
Radiometer (ESMR) on Nimbus 5 enabling all-weather mapping of sea ice extent. In
October 1978, the Scanning Multichannel Microwave Radiometer (SMMR) launched
on Nimbus 7 allowed sea ice concentrations and snow water equivalent to be delimited.
The SMMR operated until August 1987 and records have continued to the present with
the Special Sensor Microwave Imager (SSM/I) on Defense Meteorological Satellite
Program (DMSP) satellites. The Advanced Microwave Scanning Radiometer – Earth
observing system (AMSR-E) on board the Aqua satellite provides higher spatial reso-
lution (http://weather.msfc.nasa.gov/AMSR/).
The Landsat series began in 1972 and in April 1999 Landsat 7 was launched. The
Multispectral Scanner (MSS) with 80 m resolution operated through the mid 1990s, but
with Landsat 4 (1982), and Landsat 5 (1984), the Thematic Mapper (TM) with 30 m reso-
lution came into use. With Landsat 7 launched in April 1999, the Enhanced TM (ETM)
could provide data at 15 to 30 m resolution. Landsat data have been widely used for map-
ping mountain glaciers. Together with 15 m resolution data from the Advanced Spaceborne
Thermal Emission and Reflection Radiometer (ASTER) instrument (http://asterweb.jpl.
nasa.gov/asterhome/) aboard the Terra satellite, outlines for over 93,000 glaciers have been
compiled into the database of the Global Land Ice Measurement from Space (GLIMS)
project at the NSIDC.
Extensive synthetic aperture radar (SAR) data have been obtained since the 1990s.
The European Space Agency’s (ESA) Earth Remote Sensing (ERS)-1 active microwave
instrument operated between 1992–1996 and ERS-2 has been operating since 1996. The
available time series has been used to determine ice sheet mass balances. The Canadian
RADARSAT-1 sensor has been providing SAR coverage of Arctic sea ice since 1995.
In 1997 RADARSAT was rotated so that the first high-resolution mapping of the entire
Antarctic continent could be performed. The RADARSAT-II mission launched in late
2007, which carries a C-band SAR offering multiple modes of operation including quad-
polarization, ensures the continuity and improvement of SAR coverage of Arctic sea ice.
The NASA scatterometer on QuikSCAT has operated since 1999 providing another view
of sea ice extent.
ERS radar altimetry has been used to estimate ice thickness in both polar regions. In 1997
interferometry with SAR was used to obtain ice velocity vectors over the East Antarctic
ice streams. NASA’s Geoscience Laser Altimeter System (GLAS) on the Ice, Cloud, and
land Elevation Satellite (ICESat) was used to measure ice sheet elevations and changes
in elevation, as well as sea ice freeboard from February 2003 through November 2009.
Changes in mass balance of the two major ice sheets have been derived directly from the
Gravity Recovery and Climate Experiment (GRACE) of NASA launched in March 2002.
In February 2010 the European Space Agency (ESA) launched the Earth Explorer CryoSat
mission, carrying a SAR Interferometric Radar Altimeter (SIRAL). The radar altimeter is

26. Introduction
8
dedicated to precise monitoring of changes in the thickness of sea ice in the polar oceans
and variations in the thickness of the Greenland and Antarctic Ice Sheets.
Note 1.1
Ice: ice is the solid phase, usually crystalline, of water. The word derives from Old English
is, which has Germanic roots. There are other ices – carbon dioxide ice (dry ice), ammonia
ice, and methane ice – but these will not concern us here. Ice is transparent or an opaque
bluish-white color depending on the presence of impurities or air inclusions. Light reflect-
ing from ice often appears blue, because ice absorbs more of the red frequencies than the
blue ones. Ice at atmospheric pressure is approximately nine percent less dense than liquid
water. Water is the only known non-metallic substance to expand when it freezes.

27. 9
Part I
The terrestrial cryosphere
The terrestrial cryosphere forms the largest element of the overall cryosphere of the Earth
(Table 1.1). It embraces seasonal snow cover (including avalanches), glaciers and ice caps,
and the two large ice sheets of Greenland and Antarctica. It also includes perennially and
seasonally frozen ground and freshwater ice in lakes and rivers. Each of these major com-
ponents is treated in separate chapters.

29. 11
2A
2.1╇ History
The hexagonal form of snowflakes was first noted by Johannes Kepler in 1611. Robert
Hooke revealed the variety of crystalline structures as seen through a microscope in 1665.
Similar studies were performed in the mid eighteenth century in France and England.
Bentley and Humphries (1931) published a book with over 2,500 illustrations of snowflake
photographs showing a variety of snow crystals.
The earliest snow surveys were made at Mt. Rose, Nevada in 1906 by James Church, and by
1909–1910 he was surveying a network of stations. Snow surveys provide an inventory of the
total amount of snow covering a drainage basin or a given region. Church also invented the Mt.
Rose sampler€– a hollow steel tube designed so that each inch of water in the sample weighs 1
ounce (28.35 g). Snow surveying began at locations in several western states between 1919 and
1929 and in the latter year California organized cooperative snow surveys (Stafford, 1959).
In1931,apermanentCommitteeontheHydrologyofSnowwasorganizedintheHydrology
section of theAmerican Geophysical Union, chaired until 1944 by Dr. Church. By 1951 there
were about one thousand snow courses in the western states and British Columbia. A snow
course comprises an area demarcated for measuring the snow periodically during each snow
season. Usually three to eight samples are taken and averaged to determine the snow depth
and snow water equivalent for that location. Stream flow forecasting to assess water supply
is the primary objective. In remote locations aerial markers were installed; these are vertical
markers with equally spaced crossbars. The depth of snow is determined by visual observa-
tion from low-flying aircraft. The number of snow courses has declined considerably in recent
years in part due to the extension of the Snow Telemetry (SNOTEL) network. These are auto-
mated weather stations designed to operate in severe, remote mountainous environments.
Most sites collect daily, or even hourly, snow water equivalent, and precipitation and relay it
by meteor burst technology to collection stations in Boise, Idaho, or Portland, Oregon.
Remote sensing of snow cover by the Very High Resolution Radiometer (VHRR) of
NOAA (National Oceanic and Atmospheric Administration) that began in 1966 and its con-
tinuation€– theAdvanced VHRR (AVHRR)€– provides the longest time series of hemispheric
snow cover data. A variety of satellite sensors launched in the 1980s and 1990s for mapping
snow and ice are described briefly in Section 1.4. Spaceborne passive microwave measure-
ments were applied to estimate snow depth and snow water equivalent (SWE) in the late
1970s, as discussed later in this chapter. The Cold Land Processes Experiment (CLPX) of
NASA took place in the winter of 2002 and spring of 2003, in the central Rocky Mountains
of the western United States where there is a rich array of different terrain, snow, soil, and
Snowfall and snow cover

30. Snowfall and snow cover
12
ecological characteristics to test and improve algorithms for mapping snow. Through the
field campaigns of CLPX, algorithms for SWE retrieval and soil freeze/thaw status from
spaceborne passive microwave sensors, and radar retrieval algorithms for snow depth, dens-
ity, and wetness were evaluated and improved. The data were also used to improve spatially
distributed, uncoupled snow/soil models and coupled cold land surface schemes.
The National Operational Hydrologic Remote Sensing Center (NORHSC) of the
National Oceanic and Atmospheric Administration (NOAA) in the USA developed the
airborne mapping of SWE using surface-emitted gamma radiation from potassium, uran-
ium, and thorium radioisotopes in the soil. Gamma radiation is attenuated by snow cover
and absorbed by water in the snowpack (NWS, 1992), and to estimate SWE, both gamma
counts and soil moisture over snow and bare ground are needed. Such SWE data had been
used to develop passive microwave retrieval algorithms (e.g. Singh and Gan, 2000). Snow
depth can also be estimated by microwave radiation transfer models, such as that of Chang
et€al. (1987), even though such models may underestimate the snow depth, as Butt (2009)
found in a study in the United Kingdom.
2.2╇ Snow formation
Snow
The creation of saturation conditions necessary for the formation of water droplets or ice
particles occurs mainly through convection or updraft, cyclonic cooling induced by circula-
tion, frontal or non-frontal lifting of warm air, or orographic cooling by mountain barriers.
Snow forms primarily through heterogeneous nucleation. This process involves air that is
saturated having a temperature below 0 °C. Water vapor condenses and solidifies, or vapor
is deposited on nuclei, which grow into ice and snow crystals. These freezing nuclei may
be clay mineral dust (kaolinite, for example, becomes active at −9â•›°C), aerosols, pollutants,
ice crystal splinters from clouds above, or artificial seeding agents (solid CO2 or ‘‘dry ice’’,
silver iodide, or urea). The crystals may continue growing through interactions between
crystals (crystal aggregation) or with supercooled water droplets, a process called riming
(the capture of supercooled cloud droplets by snow crystals) to form snow pellets and/or
snowflakes (Mosimann et€al., 1993). The minimum size of ice crystals involved in riming is
~60 μm diameter for hexagonal plates and 30 μm width and 60 μm length for columnar ice
crystals (Ávila et€al., 2009). Under extremely low temperatures (below −40â•›°C), ice particles
can also be formed by the spontaneous freezing of water molecules, which is called homo-
geneous nucleation. Homogeneous nucleation of water droplets occurs at −40â•›°C; at −10â•›°C
approximately 1 / 106
drops freeze and at −30â•›°C about 1 / 103
drops freeze.
Ice crystal shapes are hexagonal in form from 0â•›°C to −80â•›°C and cubic form from –80â•›°C
to –130â•›°C. The reason is that a water molecule is tetrahedral; two together form a hexa-
gon, or tetrahedra offset by 60° form a cubic crystal. A cubic crystal will transform to a
hexagon if warmed but not vice versa. Crystal types have a dependence on temperature
and€saturation vapor pressure over ice. Under various combinations of temperature and

31. 2.2╇Snow formation
13
super-saturation conditions with respect to ice, a wide range of snowflakes/pellets results
(Figure€2.1). In general, as the temperature decreases, plates → needles → prisms. These
can be classified broadly as dendritic and sector plates that involve crystal growth on the
a-axis (horizontal), or columns (prisms and needles) which involve growth on the c-axis
(vertical) (Figure 2.1). Mason (1994) suggests that transitions between crystal types in
clouds can lead to more effective release of precipitation through the formation of precipi-
tation elements that have a better chance of surviving below-cloud-base evaporation.
Snowfall
Whenever snow crystals grow to a size when gravitational pull exceeds the buoyancy effect
of air, snowfall occurs. Snowfall typically reaches the ground when the freezing level is
not higher than about 250 m above the surface and the surface air temperature averages
≤1.2â•›°C. Snow may fall as snowflakes, snow grains (the solid equivalent of drizzle; white,
opaque ice particles ≤ 1 mm in diameter) or graupel (snow pellets of opaque conical or
rounded ice particles 2–5 mm in diameter formed by aggregation).
Snowflakes
Snowflakes can be classified into many types (Grey and Prowse, 1993; Sturm et€al., 1995).
Snowflakes form through the growth of ice crystals by the accretion of water vapor and by
0
0
10
20
30
40
50
60
–10 –20
Sector
Plates
Hollow
Prisms
Water Saturation
Prisms
Dendrites
Needles
Solid
Prisms
Sector
Plates
Dendrites
Solid
Prisms
Very Thick Plates
Thick Plates
Plates
–30 –40
Solid
Prisms
Cups TEMPERATURE (°C)
SUPERSATURATION
RELATIVE
TO
ICE
(%)
Figure 2.1 Types of snow crystals resulting from various combinations of temperature and supersaturation (D. Kline, after
Kobayashi, 1961).The growth of snow crystals at low supersaturations.

32. Snowfall and snow cover
14
their aggregation in branched clusters. The saturation vapor pressure is lower over an ice
surface than a water surface, reaching a maximum difference of 0.12 mb at −12â•›°C. As a
result, in a mixed phase cloud, supercooled water droplets tend to evaporate and vapor is
deposited onto ice crystals. This is known as the Bergeron–Findeisen process, after its dis-
coverers. Snowflakes grow in small cap clouds over elevated terrain when ice crystals fall-
ing from an upper cloud layer seed them. This is known as the seeder–feeder mechanism
(Barry, 2008, p. 273). When the air temperature is ≤€–40â•›°C, ice crystals may float in the
atmosphere as “diamond dust”. The designs and variations in snowflakes are way beyond
human imagination, as some examples in Figure 2.2 that show needle, sheath, and varieties
of stellar crystals with plates, dendritic and sector-like branches. Bentley, who was born in
1865, even believed that no two snowflakes are exactly alike (Teel, 1994).
Depth hoar
Other than in permafrost areas (high latitudes or high elevations in middle latitudes), the
ground is mostly warm or near freezing when the ground is snow covered. This is true even
when the air is very cold, because snow is a good insulator. Therefore, there will usually
be liquid water in the snowpack and it is common for the snow near the ground to remain
relatively warm most of the winter. Depth hoar forms at the base of a snowpack, as a result
of large temperature gradients between the warm ground and the cold snow surface, when
rising water vapor freezes onto existing snow crystals. It usually requires a thin snowpack
combined with a clear sky or low air temperature, and it grows best at snow temperatures
from –2 °C to –15 °C. Therefore, the occurrence of depth hoar is common in high Arctic
regions such as Alaska, the Northwest Territory, Nunavut, and northern Siberia (Derksen
et€al., 2009).
Depth hoar consists of sparkly, large-grained, faceted, cup-shaped ice crystals up to
10€mm in diameter. Beginning and intermediate facets are 1–3 mm square, advanced facets
can be cup-shaped 4–10 mm in size. Larger-grained depth hoar is more persistent and can
last for weeks. Depth hoar is strong in compression but not so in shear, and hence often
behaves like a stack of champagne glasses; it can fail in the form of collapsing layers, or
in shear, with fractures often propagating long distances and around corners. Almost all
catastrophic avalanches, which involve the entire season’s snow cover, fail on depth hoar
layers (Tremper, 2008).
2.3╇ Snow cover
Introduction
Snow is an integral component of the global climate system because of its linkages and its
feedbacks among surface energy, moisture fluxes, clouds, precipitation, hydrology, and atmos-
pheric circulation (King et€al., 2008). It is the second-most spatially extensive and seasonally
variable component of the global cryosphere (see Table 1.1). On average, snow covers almost

33. 2.3╇Snow cover
15
50 percent of the Northern Hemisphere’s land surface in late January, with an August min-
imum of about 1 percent. Perennial snow covers the Antarctic Ice Sheet (12 million km2
) and
higher elevations of the Greenland Ice Sheet (about 0.6 million km2
) (Figure 2.3).
Since snow produces substantial changes in the surface characteristics, and the atmos-
phere is sensitive to physical changes of the Earth’s surface, its presence over large areas
1. 2. 3. 4.
5. 6.
11.
10.
9.
8.
7.
12.
15.
14.
13. 16.
Figure2.2 ExamplesofsnowflakesclassifiedaccordingtoMagonoandLee(1966):€1.Needle,2.Sheath,3.Stellarcrystal,4.Stellar
crystalwithsectorlikeends,5.Stellarcrystalwithplatesatends,6.Crystalwithbroadbranches,7.Plate,8.Platewith
simpleextension,9.Platewithsector-likeends,10.Rimedplatewithsector-likeends,11.Hexagonalplatewithdendritic
extensions,12.Platewithdendriticextensions,13.Dendriticcrystal,14.Dendriticcrystalwithsector-likeends,15.Rimed
stellarcrystalwithplatesatends,and16.Stellarcrystalwithdendrites.Seecolorversioninplatessection.

34. Snowfall and snow cover
16
of the Earth for at least part of the year exerts an important influence on the climate, both
locally and globally. The best-known effect involves the albedo–temperature positive feed-
back, whereby an expanded (reduced) snow cover increases (decreases) the reflection of
incoming solar radiation, reducing (increasing) the temperature and thereby encouraging
an expansion (reduction) of the snow cover. Fresh snow has a spectrally integrated albedo
of 0.8–0.9, making it the most reflective natural surface. This value decreases with age to
0.4–0.7 as the snow density increases through settling and snow metamorphism, and is
reduced further by impurities in or on the snow (e.g. mineral dust, soot (Grenfell et€al.,
2010), aerosols, biogenic matter) (see Figure 2.4). The cooling effect of snow cover is
Northern Hemisphere Snow Cover Area (1966-2008)
and ± 1 Standard Deviation
0
10
20
30
40
50
60
1 2 3 4 5 6 7 8 9 10 11 12
Month
Averaged
Monthly
Snow
Cover
Area
(million)
km
2
Figure 2.3 Averaged monthly snow cover area of Northern Hemisphere in (x 106
) km2
calculated from weekly snow cover extent
maps produced primarily from daily visible satellite imagery of NOAA-AVHRR by the Rutgers Global Snow Lab.
0
O D F Ap
near IR
all solar
radiation
visible
albedo
albedo
Jn Au
O D F Ap Jn Au
0.25
0.5
0.75
1
0
0.25
0.5
0.75
1
2003 2005
Figure 2.4 Field measurements of broadband albedo at Mammoth Mountain in the Sierra Nevada for (a) 2003 and (b) 2005,
showing albedo in the visible, near-infrared, and all solar radiation (adapted from Dozier etal., 2009, Fig. 1, S26).

35. 2.3╇Snow cover
17
illustrated by the example that, in the Upper Midwest of the United States, winter months
with snow cover are about 5–7â•›°C colder than the same months without snow cover. Snow,
a poor conductor of heat, also insulates the soil surface and sea ice. Therefore a better
knowledge of the snow cover and its properties over large regions will lead to a better
understanding of our climate.
Snow stores water until there is sufficient energy to melt or sublimate it to water vapor.
The storage of water in the seasonal snow cover introduces into the hydrological cycle an
important delay of weeks to months, causing a peak in the annual runoff in spring and early
summer when the river water is agriculturally more valuable. It is highly beneficial to be
able to estimate the amount and timing of release of this stored precipitation to spring runoff,
which allows a better management of water resources for irrigation and hydroelectric pro-
duction planning. The dynamics of water storage in seasonal snowpack is also critical to the
effective management of water resources globally. Snow water accumulated in winter in the
Arctic river basins is critical for the springtime snowmelt, and the freshwater from its river
systems accounts for about 50 percent of the net flux of freshwater into the Arctic Ocean
(Barry and Serreze, 2000), which is a large percentage when compared to the freshwater
inputs to the tropical oceans, where freshwater input is dominated by direct precipitation.
Frozen soil affects the snowmelt runoff and soil hydrology by reducing the soil permeability.
Runoff affects ocean salinity and sea ice conditions (Peterson et€al., 2002) and the degree of
surface freshening can affect the global thermohaline circulation (Broecker, 1997).
Snowpacks affect energy and water exchanges, so snow cover and snow water equiva-
lent (SWE) are important climatic and hydrologic variables. In particular, snow controls
the climate and hydrology of the cryosphere and higher latitude regions significantly,
and€the amount and distribution of snow is affected by the climate and vegetation types.
In the Canadian Prairies, mixed precipitation can occur within a certain range of tem-
perature (Kienzle, 2008), but on the whole approximately one-third of its annual precipi-
tation occurs as snowfall, and the shallow snow cover generates as much as 80 percent
of€the annual surface runoff. In the Colorado Rockies, the Sierra Nevada of California, and
the€Cascade Mountains of Washington, snowmelt can account for up to 65–80 percent of
the annual water supply (Serreze et€al., 1999).
The snow covers of North America and Eurasia change seasonally, in accordance
with the position of the Sun that shines directly at the Tropics of Cancer in the Northern
Hemisphere on June 21 (summer solstice) and then moves southward, reaching the Tropics
of Capricorn in the Southern Hemisphere on December 22 (winter solstice), before mov-
ing northward for the next 6 months; the cycle repeats itself on an annual time scale. The
extent of snow cover in the Northern Hemisphere (NH) lands reaches an average max-
imum of about 46.8â•›×â•›106
km2
in January and February, and an average minimum of about
3.4â•›×â•›106
km2
in August (see Figure 2.5) (Ropelewski, 1989; Robinson, 2008; Brown and
Armstrong, 2008), which constitute 8 percent and about 0.5 percent of the Earth’s surface,
respectively. From 1966 to 2008, the maximum January snow cover of the NH ranged from
as low as 42â•›×â•›106
km2
(1982) to as high as 50.1â•›×â•›106
km2
(2008) (GSL, 2008). For 1966 to
2008, the mean annual NH snow extent was 25.5â•›×â•›106
km2
(Robinson, 2008).
In the NH, most mid-summer snow cover is found over Greenland and some parts of the
Canadian high Arctic (Figure 2.5 d), while about 60 percent of winter snow cover is found

36. Snowfall and snow cover
18
April
July
January
January
(a)
(c)
(d)
(b)
North Pole
snow extent
sea ice extent
January
(e)
(f) July
Figure2.5 SeasonalvariationinthemeanmonthlysnowandseaicecoverextentforJanuary(a,b),April(c),andJuly(d)over€the
NorthernHemisphere(NH)usingdataofNSIDC(NationalSnowandIceDataCenter)over1967–2005forsnow
and1979–2005forice;forJanuary(e)andJuly(f)overAntarctic/Southern Hemisphereover1987–2002forsnow
and1979–2003forice(Maurer,2007)byLambertAzimuthal Equal-Area(http://nsidc.org/data/atlas)Â�projection;
January31,2008snowandicechartofNHadaptedfromNOAA-AVHRR imageofNOAA(http://wattsupwiththat.
com/2008/02/09/jan08-northern-hemisphere-snow-cover-largest-since-1966/). Seecolorversioninplatessection.

37. 2.3╇Snow cover
19
over Eurasia and 40 percent over Canada and the upper portion of the U.S.A., sometimes
down to latitude 30° N (Figure 2.5 a and b). Figure 2.6 a, b, c, d are composite monthly
NOAA-AVHRR images of North America that show large seasonal variations in snow
cover among the four seasons. In contrast, in South America, there is only a small area
covered with snow in July.
Snow cover is observed in situ at hydrometeorologcal stations, from daily depth meas-
urements, (monthly) snow courses, and in special automated networks such as about 730
SNOwpack TELemetry (SNOTEL) automated systems of snow pressure pillows, sonic
snow depth sensors, precipitation gauges, and temperature sensors distributed across the
USA. The extent of snow cover is also observed and has been mapped daily (since June
1999) over the NH from operational NOAA satellites (Barry, 2009b).
Canada has extensive in situ snow depth and snow course networks which are a valuable
database for monitoring cryospheric changes and for validating satellite data such as those
shown in Figures 2.5 and 2.6. However, most of the field observations are concentrated
in southern latitudes and lower elevations, where the majority of the population lives. At
many northern sites manned stations have been replaced by automatic weather station
(AWS) that use acoustic sounders to measure the height of the snow surface.
Besides seasonal variability, snow cover is subject to inter-annual fluctuations, but only
about 40 percent of these have been found to be associated with continental to hemispheric
scale forcing (Robinson et€al., 1995), and the rest could be partly attributed to regional
(a) July (b) October (c) January (d) April
(e) Snow-free forests (dark green), unforested areas with snow cover (gray), and forests
with snow cover (red) are shown
Figure 2.6 Seasonal variation in the mean monthly snow cover extent for (a) July, (b) October, (c) January, and (d) April over
North America computed from snow charts derived from weekly visible satellite images of NOAA-AVHRR over
1972–1993 (www.tor.ec.gc.ca/CRYSYS/cry-edu.htm); (e) Northern Hemisphere snow and forest covers for January,
2005 computed from the National Snow and Ice Data Center (NSIDC) Equal-AreaScalable Earth Grid (EASE-Grid) snow
cover product (Armstrong and Brodzik, 2005) and the University of Maryland global land cover classification (Hansen
etal., 1998) (taken from Figure 1, pg. 3 of Essery etal., 2009). See color version in plates section.

38. Snowfall and snow cover
20
forcings or “coherent” regions. By Principal Components Analysis (PCA) and composite
analysis, Frei and Robinson (1999) found that over western North America (NA), snow
cover extent is associated with the longitudinal North American ridge, the PNA (Pacific
North America) index, while over eastern NA, it is associated with the meridional oscil-
lation of the 500-mb geopotential height, the NAO (North Atlantic Oscillation), and the
teleconnection patterns are coupled to tropospheric variability during autumn and winter.
Gobena and Gan (2006) found during El Niño winters, the southeasterly flow of warm dry
Pacific air and the northwesterly flow of cool dry Arctic air will be the dominant flow over
western Canada and the Pacific Northwest (PNW) of the USA, giving rise to drier climate
(less snowfall) over these regions. On the other hand, La Niña winters are associated with
an erosion of the western Canadian ridge and strengthening of the Pacific Westerly, giving
rise to greater moisture supply and so more winter snowpack in western Canada and the
PNW of the USA.
Besides solar radiation, snowpacks are related to surface air temperature, precipitation,
storm tracks, and mid-tropospheric geopotential heights at 500 mb. Lamb (1955) and Frei
and Robinson (1999) showed that snow extent, by exerting an influence on lower tropo-
spheric thickness, could even modulate atmospheric circulations. Brown (2000) observed
some decline in northern hemispheric snow cover in recent decades but the declines are
not statistically significant. However, Brown et€al. (2000) found that snow cover in Canada
experienced major contractions during the 1990s.
From 1972 to 2000, using weekly NH snow cover data of high latitude and high eleva-
tion areas derived from visible-bands of NOAA satellite observations, Dye (2002) found
that the week of the last-observed snow cover in spring shifted earlier by 3–5 days/dec-
ade estimated from a linear regression analysis, and the duration of the snow-free period
increased by 5–6 days/decade, primarily as a result of earlier snow cover disappearance
in spring. Similarly, in a sensitivity study based on the 1966–2007 snow cover data of
NOAA satellites and simulations from the Coupled Model Intercomparison Project phase
3 Model (CMIP3), on the response of NH land area with seasonal snow cover to warming
and increasing precipitation, Brown and Mote (2009) found snow cover duration (SCD)
was the snow cover variable exhibiting the strongest climate sensitivity, especially in the
coastal mountains of western NA with extensive winter snowfall. They found the largest
decreases were concentrated in a zone where seasonal mean air temperatures were in the
range of –5 to +5â•›°C which extended around the mid-latitudinal coastal margins of the
continents. Regional studies in the western USA (Adam et€al., 2009) suggest that losses
of snowpack associated with warming trends have been ongoing since the mid twentieth
century, especially near boundaries of areas that currently experience substantial snowfall.
These findings very likely reflect clear signals of human-induced impact on the climate
shown by the changing snowpacks of NH and by the river flows of western USA (Barnett
et€al., 2008).
For mountainous regions, Stewart (2009) found that higher temperatures have decreased
snowpack and resulted in earlier melt in spite of precipitation increases at mid-elevation
regions but not at high-elevation regions, which remain well below freezing during winter.
With continued warming, Stewart projected that increasingly higher elevations will experi-
ence declines in snowpack accumulation and melt that can no longer be offset by winter

39. 2.3╇Snow cover
21
precipitation increases. On the other hand, based on their sensitivity analysis of snow cover
in NH, Brown and Mote (2009) postulated a more complex elevation response of SCD and
SWE to increasing temperature and precipitation in mountainous regions because of non-
linear interactions between the duration of the snow season and snow accumulation rates.
Snow cover, depth distribution, and blowing snow
At continental scales or larger, snow cover distribution primarily depends on latitude and
seasons (Figures 2.5 and 2.6). At the macro or regional scale, for areas up to 106
km2
, and
distances from 10 to 1000 km, snow cover distribution depends on latitude, elevation,
orography, and meteorological factors. For example, snowfall caused by orographic cool-
ing tends to increase with a rise in elevation, and frontal activities involving cold fronts
generally produce more intense snowfall over relatively smaller areas as against warm
fronts that produce moderate or light snowfall over larger areas, because the former has a
relatively steep leading edge while the latter has a gentle leading edge. On the mesoscale,
with distances of 100 m to 10 km, snow distribution depends on the blowing effect of
wind, relief, and vegetation patterns, while on the micro-scale, 10 to 100â•›m, the influencing
factors are more local. Over highly exposed terrain, the effects of meso- and micro-scale
differences in vegetation and terrain features may produce wide variations in accumulation
patterns and snow depths.
Blowing snow occurs when the force of wind exceeds the shear strength of the snow-
pack surface resisting snow particle movement. Blowing snow increases with wind speeds
and the amount of snowfall but decreases with increasing surface roughness. The effects
of wind on the accumulation and distribution of a snowpack are most pronounced in open
environments, e.g. the Canadian Prairies or Siberian steppes, with three modes of snow
particle movement:€snow particles begin in motion by creeping or rolling on snowpack
surface, then by saltation or bouncing when wind speed increases, and finally in turbulent
diffusion with snow particles suspended in the air under high wind speed. These three
modes of transport typically occur less than 1 cm above ground under a low wind speed
U ( 5 m s−1
), between 1 to 10 cm for U = 5–10 m s−1
, and between 1 and 100â•›m for U
10€m€s−1
, respectively.
Based on wind tunnel studies with surface wind speeds of up to 40 m s−1
, Dyunin et€al.
(1977) argued that saltation accounts for most drifting snow at all conceivable wind speeds.
However, Budd et€al. (1964) found that turbulent suspension was the primary mechan-
ism from snowdrift studies at Byrd Station, Antarctica. Suspension increases at about U4
,
whereas saltation increases linearly with U at high wind speeds (at which most transport
occurs), so suspension dominates the overall effect of wind (Pomeroy and Gray, 1990;
Pomeroy, p.c. Dec. 2009). At low wind speeds, saltation is the dominant process.
Blowing snow is important in open environments, especially for high elevation alpine
areas above the treeline, in the Prairies, and in the Arctic tundra. In these regions snow
depth variation depends mainly on terrain features because without the hindering effect
of vegetation cover, wind causes snow drift and re-distribution to smooth topography, so
that mountain tops and plateaus tend to have thin snowpack as snow tends to be blown to
valleys and low lying areas which as a result tend to have relatively thick snowpack. In the

40. Snowfall and snow cover
22
coastal tundra and open sub-Arctic forest of Canada, near Churchill, Manitoba, Kershaw
and McCulloch (2007) found that snowpack characteristics measured from 2002 to 2004
also depend on vegetation characteristics, ecosystems, and associated micro-climates.
Ecosystems that dominate the circumpolar north are for example, wetland, black and white
spruce forest, burned forest, forest–tundra transition, and tundra. In lower latitudes as the
forest canopy density generally increases, higher snow accumulation has been found in
forests of medium density (25 to 40%) than large open areas because of wind effects, or
densely forested areas because of the sublimation of intercepted snow (e.g. Veatch et€al.,
2009).
Gordon et€al. (2009) developed a camera system to measure the relative blowing snow
density profile near the snow surface in Churchill, Manitoba, and Franklin Bay, Northwest
Territory. Within the saltation layer, they found that the observed vertical profile of mass
density is proportional to exp(–0.61 z/H), where H, the average height of the saltating par-
ticles, varies from 1.0 to 10.4 mm, while z, the extent of the saltation layer, varies from 17
to over 85 mm. At greater heights, z 0.2 m, the blowing snow density varies according to
a power law (ρs ∝ z−ɤ
), with a negative exponent 0.5 γ 3. Between these saltation and
suspension regions, results suggest that the blowing snow density decreases following a
power law with an exponent possibly as high as γ ≈ 8.
2.4╇ Snow cover modeling in land surface schemes of GCMs
Snow cover is treated in Land Surface Models (LSMs,) but snow and ice–albedo parameter-
izations differ widely in their complexity (Barry, 1996). The Snow Model Intercomparison
Project (SnowMIP) was conducted using 24 snow cover models developed in ten different
countries (Essery and Yang, 2001). The models differed from single versus multi-layers,
with and without a soil model, variable versus constant heat conductivity and snow density,
and the treatment of liquid storage. Only four of the 24 models met€all the five criteria.
Twenty seven atmospheric general circulation models (GCMs) were run under the aus-
pices of the Atmospheric Model Intercomparison Project (AMIP)-I. The GCMs of AMIP-I
reproduced a seasonal cycle of snow extent similar to the observed cycle, but they tended
to underestimate the autumn and winter snow extent (especially over North America)
and overestimated spring snow extent (especially over Eurasia). The majority of models
displayed less than half of the observed inter-annual variability. No temporal correlation
was found between simulated and observed snow extent, even when only months with
extremely high or low values were considered (Frei and Robinson, 1995). The second gen-
eration AMIP-II simulations gave better results (Frei et€al., 2003).
Slater et€al. (2001) found that various snow models in land surface schemes could model
the broad features of snow cover and snowmelt processes for open grasslands on both
an intra- and an inter-annual basis. On the other hand, modeling the spatial variability of
snow cover is more problematic because this requires careful consideration of blowing
snow transport and sublimation, canopy interception, and patchy snow conditions, which
are difficult to parameterize accurately, given that energy fluxes are mostly modeled only

41. 2.4╇Snow cover modeling in land surface schemes of GCMs
23
in the vertical direction. Woo et€al. (2000) made some progress in understanding several
such processes at a local scale, but most land surface schemes and climate models do not
account for the subgrid variability of snow cover in each grid cell.
To realistically simulate grid-averaged surface fluxes, Liston (2004) developed a
Subgrid SNOW Distribution (SSNOWD) submodel that explicitly considers the changes
of snow-free and snow cover areas in each surface grid cell as the snow melts, by assum-
ing SWE distributes according to a lognormal distribution and the snow-depth coefficient
of variation (CV). Using a dichotomous key based on air temperature, topographic vari-
ability, and wind speed, Liston proposed a nine-category, global distribution of subgrid
snow-depth-variability, each category being assigned a CV value based on published data.
The SSNOWD then separately computed surface-energy fluxes over the snow-covered
and snow-free portions of each model grid cell, weighing the resulting fluxes according
to these fractional areas. Using a climate version of the Regional Atmospheric Modeling
System (ClimRAMS) over a North American domain, SSNOWD was compared with a
snow-cover formulation that ignores sub-grid snow-distribution. The results indicated that
accounting for snow-distribution variability has a significant impact on snow-cover evolu-
tion and associated energy and moisture fluxes.
Modeling blowing snow
Pomeroy et€al. (1993) developed the first comprehensive blowing snow model for the prai-
ries environment. It estimates saltation, suspension, and sublimation using readily available
meteorological data. They show that within the first 300 m of fetch, transport removes 38–85
percent of the annual snowfall. However, beyond one kilometer of fetch, sublimation losses
from blowing snow dominate over transport losses. In Saskatchewan, sublimation losses are
44–74 percent of annual snowfall over a 4 km fetch. Subsequently, Pomeroy (2000) showed
that the ratio of snow removed and sublimated by blowing snow to that transported at prairie
(arctic) sites was 2:1 (1:1), respectively.
Essery et€al. (1999) developed a distributed model of blowing snow transport and sub-
limation to consider physically based treatments of blowing snow and wind over complex
terrain for an Arctic tundra basin. By considering sublimation, which typically removes
15–45 percent of the seasonal snow cover, the model is able to reproduce the distributions
of snow mass, classified by vegetation type and landform, which they approximated with
lognormal distributions. The representation used for the downwind development of blow-
ing snow with changes in wind speed and surface characteristics is shown to have a mod-
erating influence on snow redistribution. In the Colorado Rocky Mountains, spatial fields
of snow depth have power spectra in one and two dimensions that occur in two frequency
intervals separated by a scale break between 7 and 45 m (Trujillo et€al., 2007). The break in
scaling is controlled by the spatial distribution of vegetation height when wind redistribu-
tion is minimal and by the interaction of the wind with surface concavities and vegetation
when wind redistribution is dominant.
In mountainous regions, wind plays a prominent role in determining snow accumula-
tion patterns and turbulent heat exchanges, strongly affecting the timing and magnitude of
snowmelt runoff. Winstral and Marks (2002) use digital terrain analysis to quantify aspects

42. Snowfall and snow cover
24
of the upwind topography related to wind shelter and exposure. They develop a distrib-
uted time-series of snow accumulation rates and wind speeds to force a distributed snow
model. Terrain parameters were used to distribute rates of snow accumulation and wind
speeds at an hourly time step for input to ISNOBAL, an energy and mass balance snow
model which accurately modeled the observed snow distribution (including the formation
of drifts and scoured wind-exposed ridges) and snowmelt runoff. In contrast, ISNOBAL
forced with spatially constant accumulation rates and wind speeds taken from the sheltered
meteorological site at Reynolds Mountain in southwest Idaho, a typical snow-monitoring
site, over-estimated peak snowmelt runoff and underestimated snowmelt inputs prior to the
peak runoff.
Liston and Elder (2006) developed a spatially distributed, physics-based, snow-evolution
model (SnowModel) that uses meteorological data, surface energy fluxes, topography and
vegetation to simulate snow accumulation, canopy interception, snow-density evolution,
snowpack melt, and blowing-snow redistribution and sublimation by wind for a variety of
environments:€ice, tundra, taiga, alpine/mountain, prairie, maritime, and ephemeral. Liston
and Elder (2006) demonstrated that SnowModel could closely simulate observed SWE dis-
tribution, time evolution, and inter-annual variability patterns in both forested and nonfor-
ested landscapes, but the model has not been tested in a mountainous environment. A data
assimilation component (SnowAssim) for assimilating ground-based and remotely sensed
snow data within SnowModel was also developed (Liston and Hiemstra, 2008), with the
aim of improving the simulation of snow-related distributions throughout the entire snow
season, even when observations are only available late in the accumulation and/or ablation
periods. SnowAssim was found to simulate more realistic spatial distributions of SWE than
that provided by the observations alone for the observation domain of NASA’s Cold Land
Processes Experiment (CLPX), Rabbit Ears Pass, Colorado.
2.5╇ Snow interception by the canopy
Snowfall can be intercepted by an over-story canopy and so below the treeline, snow depth
variation depends more on landuse or vegetation types such as coniferous or broadleaf
forests with different canopy structure (Gan, 1996). Snow falling on a canopy is influenced
by two possible phenomena:€(1) Turbulent air flow above and within the canopy may lead
to variable snow input rates and microscale variation in snow loading on the ground, (2)
Direct interception of snow by the canopy elements may either sublimate or fall to the
ground. Interception processes are related to vegetation type (deciduous or evergreen),
vegetation density, needle characteristics, canopy form and area, branch orientation, LAI
(leaf area index), and the presence of nearby open areas. Increasing air temperature tends to
increase the cohesiveness of snow and so increase the amount of intercepted snow retained
in the canopy. For forested environments, most studies show greater snow accumulation in
open areas than in forest even though redistribution of intercepted snow by wind to clear-
ings is not typically a significant factor. Instead, interception by canopy and subsequent
sublimation which constitutes the interception loss are the major factors contributing to the

43. 2.5╇Snow interception by canopy
25
difference. Intercepted snow can also melt and then be released to the ground snowpack
through meltwater drip, mass release, or flow down the stems of plants as stemflow.
Snow intercepted by the canopy also constitutes part of the overall accumulation of
snowfall. Snow is intercepted and stored at different levels of vegetation until the max-
imum interception storage capacities are reached. Maximum interception storage capaci-
ties associated with different vegetation are determined from projected leaf area index
from canopy top to ground per unit of ground area, or leaf area index LAI (Dickinson et€al.,
1991). An example algorithm to estimate snow intercepted by the canopy is
I c I I e
su o
C P
I
c s
= −
( ) −
* *
1 (2.1)
where I (kg m−2
), the snow interception, is related to a snow unloading coefficient, csu, the
maximum snow load, I*, initial snow load, Io (kg m−2
), an exponential function of snowfall,
Ps (kg m−2
per unit time), snow density ρs the canopy density, Cc, and coefficient Sp which
depends on vegetation species, and I S LAI
p
s
f
*
.
= +
0 27
46
ρ
. Cumulative snow interception on
isolated coniferous trees has been shown to follow a number of probability distributions,
ranging from linear to a logistic distribution of the form (Satterlund and Haupt, 1967),
I
I
e K Ps Ps ip
=
+ − −
*
( , )
1
(2.2)
Here, K = rate of interception storage (mm−1
), Ps = SWE of a snowfall event (mm), and
Ps,ip = SWE of snowfall at inflection point on a sigmoid growth curve (mm).
The canopy of certain forest types can intercept substantial amounts of snowfall (Figure
2.7), which alters both the accumulation of snow on the ground as well as snowmelt rates
(Hardy and Hansen–Bristow, 1990). Therefore the distribution of snow on the forest floor
Figure 2.7 Snow intercepted by canopy.

44. Snowfall and snow cover
26
is affected differently depending on the tree species and the prevailing forest structure
(Golding and Swanson, 1986). While coniferous forests typically form tree wells around
the stems during winter, leafless deciduous forests give rise to snow cones at tree trunks
(Sturm, 1992). The overall effect of most forest canopies is a snowpack with spatially
heterogeneous depth and snow water equivalent (SWE). Pomeroy and Schmidt (1993)
observed that SWE beneath the tree canopy is equal to 65 percent of the undisturbed snow
in the boreal forest. In contrast, Hardy et€al. (1997) measured 60 percent less snow in bor-
eal jack pine tree wells than in forest openings at maximum accumulation.
Hedstrom and Pomeroy (1998) developed a physically based snowfall interception
model that scales snowfall interception processes from branch to canopy, and takes account
of the persistent presence and subsequent unloading of intercepted snow in cold climates.
To investigate how snow is intercepted at the forest stand scale, they collected measure-
ments of wind speed, air temperature, above- and below-canopy snowfall, accumulation
of snow on the ground and the load of snow intercepted by a suspended, weighed, full-size
conifer from spruce and pine stands in the southern boreal forest. Interception efficiency
was found to be particularly sensitive to snowfall amount, canopy density and time since
snowfall. Further work resulted in process-based algorithms describing the accumulation,
unloading, and sublimation of intercepted snow in forest canopies (Pomeroy et€al., 1998).
These algorithms scale up the physics of interception and sublimation from small scales,
where they are well understood, to forest stand-scale calculations of intercepted snow sub-
limation. However, under windy and dense vegetation environments, blowing snow and
canopy interception of snow are two key factors contributing to the re-distribution of snow-
fall that are still challenging in snow hydrologic applications.
2.6╇ Sublimation
Besides redistribution, another major influence of the wind transport of snow is sublimation,
a special form of evaporation, whereby solid ice is transformed directly to atmospheric
water vapor. Sublimation involves the latent heat of fusion (lfs = 333 kJ kg−1
) for ice to water
plus the latent heat of vaporization for water to vapor (lv ≈ 2501 kJ kg−1
). Hence it requires
~7.5 times the amount of energy required for snowmelt. Sublimation depends on ground
surface conditions, wind speed, humidity, net solar radiation, and atmospheric stability. It
may account for less than 10 percent of the annual snowfall, but could increase substantially
under dry, warm, and windy winter conditions, with snowpack losses reaching 80 percent
under extreme situations (Beaty, 1975). For a given weather condition, forest cover (types
and densities) could reduce sublimation on the ground by controlling the amount of net solar
radiation reaching the ground and by reducing the wind speed. On the other hand, sublim-
ation of canopy-intercepted snow tends to increase with denser stands, high leaf area index,
and tall trees. Furthermore, strong positive net radiation alone tends to increase melting over
sublimation, and the effect of forest cover diminishes during atmospheric inversions.
Snow sublimation occurs from the ground and the forest canopy, but most efficiently
from wind-induced, turbulent snow transport. Sublimation from blowing snow can

45. 2.6╇Sublimation
27
consume about 20 percent of the snow in the Sierra Nevada (Kattelmann and Elder, 1991),
30 to 50 percent in Colorado (Berg, 1986), and 10 to 90 percent in Alpine mountains when
snow is under turbulent suspension on wind-exposed mountain ridges (Strasser et€al.,
2008). In western Canada, snow sublimation during winter can amount to 40 percent
of the seasonal snowfall, or 30 percent of the annual snowfall (Woo et€al., 2000). In the
Canadian Prairies, sublimation may amount to over 50 mm of SWE per year or about
30 percent of the annual snowfall. Zhang et€al. (2004) noted that in the taiga of eastern
Siberia, the Tianshan, eastern Tibetan Plateau, and Mongolia, sublimation could be large,
in particular under neutral atmospheric conditions. Hood et€al. (1999) calculated sublim-
ation from the seasonal snowpack for nine months during 1994–1995 at Niwot Ridge in
the Colorado Front Range using the aerodynamic profile method. They calculated latent
heat fluxes at ten-minute intervals and converted them directly into sublimation or con-
densation at three heights above the snowpack. The total net sublimation for the snow
season was estimated at 195 mm of water equivalent (w.e.) or 15 percent of the maximum
snow accumulation; monthly sublimation during fall and winter ranged from 27 to 54 mm
w.e., and daily sublimation often showed a diurnal periodicity with higher rates of sub-
limation during the day.
Sublimation of blowing snow within the near-surface atmospheric boundary layer can
deplete the snow mass flux, especially under relatively arid, warm, and windy winter con-
ditions. It is also sensitive to air temperature, wind speed, particle size, relative humidity,
and terrain features. Often, for extensively flat areas fully covered with snow, the atmos-
pheric boundary layer near the surface is sufficiently developed to assume a steady mass
flux of blowing snow.
A popular algorithm for estimating snow sublimation is in the form of Dalton’s law.
In this, the depth of snow sublimation, Ds (cm) is a function of average wind speed (ūb)
at height zb above the snowpack, the vapor pressures (es and ea) at snowpack level and at
height za above the snowpack, ρw is the density of water,
= +
D E l l
s e v fs w
( )
/ ,
ρ (2.3)
where Ee is the energy used for snow sublimation, given as
E
k
P
u e e z z t
e
a
b s a a b
=





 − −
1 1 6
6
0 622
.
( )( ) ( ).
/
∆ (2.4)
The constant, k1 = 0.00651 cm m−1/3
hr day−1
mb−1
km−1
, Δt the time step, and Pa the atmos-
pheric pressure. The snowpack depth change due to sublimation (ΔDs) is given as
∆D D
s
w
s
s
=
ρ
ρ
, (2.5)
where ρs is the density of the snowpack. A simpler way to estimate Ee is
E B U e e
e e s a
= −
( ), (2.6)

46. Snowfall and snow cover
28
where Be is the bulk transfer coefficient for turbulent exchange above the melting
snow. The above equations are designed to estimate snow sublimation in windy envi-
ronments. Snow models that simulate snow sublimation include the Alpine MUltiscale
Numerical Distributed Simulation Engine (AMUNDSEN) of Strasser et€al. (2008), and the
SnowTran-3D of Liston et€al. (2007).
2.7╇ Snow metamorphism
Over time, a snowpack will undergo compaction as ice crystals metamorphose, and set-
tle, which is partly due to increasing overburden load as snowfall occurs. As the winter
progresses, snow depth generally decreases while snow density increases as snow meta-
morphoses from low density, fine grains to high density, coarse grains, isothermal snow-
pack with higher liquid permeability and thermal conductivity. Depending on the location,
changes to snowpack properties via metamorphism may happen mainly in the spring, or
happen periodically, or only at the surface, but the degree of metamorphism will depend
on the climate and whether the snow is wet or dry. The amount of SWE should theoretic-
ally remain unchanged, unless it is reduced by sublimation. As vapor pressure is higher in
warmer than in cooler snowpack, and over convex rather than concave ice surfaces because
of differences in the radius of curvature, there will be vapor diffusion from warmer to
cooler locations, over crystal surfaces and between snow grains, resulting in irregular ice
crystals transforming into well-rounded, coarser grains, even depth hoar. Mass and energy
transfer by vapor pressure and temperature gradient can also give rise to faceted snow
crystals of various shapes and patterns.
The freeze-thaw cycles of snowpack dictated by the diurnal temperature cycle (warm
day and cold night) causes melting of small grains and then refreezing to rounded, large-
grained snowpacks, and possibly the formation of firn (see Section 3.2) and glacial ice.
In wet snow, small ice crystals tend to melt first, and when the meltwater refreezes, it is
absorbed by the larger snow grains which tend to grow more rapidly under more liquid
water since water is a better conductor of heat than air. Under increasing pressure, snow is
compressed and slowly deforms to firn and then to ice (Colbeck, 1983).
By definition, the density of snow ρp is given as ρp = ρi(1-ϕ) + ρwWliqϕ where ρi is the
density of ice, ϕ the porosity of snowpack, ρw the density of water and Wliq the liquid water
content in the snowpack. Newly fallen snow normally has a density ρp of about 100 kg m−3
or less, an albedo of 90 percent (α = 0.9) or higher, and grain size of 50 μm to about 1 mm,
but the grain size and density will increase as snow ages. Snow grains are considered very
fine if they are less than 0.2mm, fine if 0.2 to 0.5 mm, medium if 0.5 to 1 mm, coarse if
greater than 1 mm, and very coarse if greater than 2 mm (Fierz et€al., 2009). Snow hardness,
which can be measured by the force in Newtons (N) needed to penetrate with an object such
as the SWISS rammsonde, or by a hand hardness index (De Quervain, 1950), is expected to
increase as snow settles. Snow hardness ranges from very soft with hardness index ranges
from 1 (penetration force 50 N), to 5 or very hard (up to 1200 N), respectively. Table 2.1
gives a breakdown of snow types and typical densities, and snow grain shapes encountered

47. 2.7╇Snow metamorphism
29
during the process of metamorphosis shown in Figure 2.8. According to Sturm et€al. (1997),
the thermal conductivity of snow is primarily dependent on snow density even though ice
grain structure and temperature are also controlling factors. Sublimation will cause a thinner
snow cover, or reduced SWE, but not necessarily reduce the snow-cover area. Hence, it is
difficult to detect the effect of sublimation from snow-cover data.
There is a strong connection between snow properties and land surface water and energy
fluxes that influence weather and climate all over the cryosphere. The variability of the
snowpack significantly influences the water cycle globally, and especially at high lati-
tudes. The snow-covered area (SCA) exhibits a fairly wide range of spatial and temporal
Table 2.1╇ Density of typical snow covers
Snow type Density ρp (kg m−3
)
Wild snow 10 to 30
Ordinary new snow immediately after falling in still air 50 to 65
Settling snow 70 to 100
Average wind-toughened snow 250 to 300
Hard wind slab 320 to 400
New firn snow 400 to 550
Advanced firn snow 550 to 650
Thawing firn snow 600
Early rounding Faceted growth Early sintering
(bonding)
Wind-blown grains
Melt–freeze with
no liquid water
Melt–freeze with
liquid water
Faceted layer growth Hollow, faceted
grain (depth hoar)
Figure 2.8 Snow grain shapes under different stages of metamorphosis (Don Cline, NOHRSC, NationalWeather Service, USA).

48. Snowfall and snow cover
30
fluctuations seasonally, which in turn affect the variability in the surface albedo and
�
radiation balance, vapor fluxes to the atmosphere through sublimation and evaporation,
and meltwater infiltrating into the soil and river systems. This seasonal and inter-annual
variability of snowpacks affects the general circulation of the atmosphere (Walland and
Simmonds, 1997).
Snow cover extent has been shown to exhibit a close negative relationship with hemi-
spheric air temperature over the post-1971 period (Robinson and Dewey, 1990). The
snow–temperature relationship is strongest in March, when the largest warming and most
significant reduction in snow cover extent have been observed in both Eurasia and North
America since 1950 (Brown, 2000).Arctic summer temperature increases have been tied to
an increase in the number of snow-free days, and to a lesser extent the change from tundra
to a “shrubbier” Arctic (Chapin et€al., 2005).
In terms of wetness, snow is classified as dry if its liquid water content (Wliq), or the per-
cent of liquid water by weight in the snow pack is near 0 percent and there is little tendency
for snow grains to stick together, which usually happens when the snowpack temperature
Tp ≤ 0â•›°C. When Wliq reaches about 3 percent, snow is considered moist and it has a distinct
tendency to stick together, and Tp ≈ 0â•›°C. Beyond 3 to 8 percent of Wliq, snow is considered
wet, 8 to 15 percent of Wliq as very wet when water can be squeezed out by hand, and slushy
or soaked when Wliq exceeds 15 percent and Tp 0â•›°C (Fierz et€al., 2009). When Tp 0â•›°C,
the pores can hold water mostly by capillarity and tension. Because of liquid water, it can
be shown that
L
L
W
ms
fs
liq
= −
1
100
, (2.7)
where Lfs = latent heat of fusion of pure ice, and Lms = latent heat of fusion of snow. Because
of the presence of liquid water in most snowpacks, Lms is usually less than Lfs, which is
about 333 KJ kg−1
.
The ground snowpack can exist in a number of layers, with the surface layer subjected
to high frequency energy and water exchanges with the atmosphere, while the lower layers
undergo heat exchanges through conduction and infiltration of meltwater flow downwards.
Snow grains become coarser and, as the snowpack ages, its density increases and it becomes
compressed by further snowfall. However, density could decrease over time if there were a
substantial amount of depth hoar in the snowpack (Hiemstra, personal communication).
2.8╇ Insitu measurements of snow
Ground snowfall data are collected using a ruler, a snow board or a snow pillow, non-
recording snow gauges such as the MSC snow gauge with a Nipher shield in the shape of
an inverted bell to reduce wind effects on precipitation collectors, the Swedish SMHI pre-
cipitation gauge, and the USSR Tretyakov gauge. Nonrecording gauges can be read daily
or over a period of time, such as monthly or by seasons, but that requires anti-freeze such

49. 31 2.8╇ Insitu measurements of snow
as propylene glycol mixed with ethanol and evaporation suppressants such as mineral oil,
and such gauges are elevated to prevent them from being inundated by a possible heavy
accumulation of snow. Weighing-type, self-recording snow gauges such as the Fisher
Porter and universal gauges that measure temporal snowfall data using a spring, transmit
the data via satellite to a data collection center, or lately by tipping buckets connected to
data-loggers from which recorded data can be downloaded. With ground measurements of
snowfall, the catch of solid and mixed precipitation in precipitation gauges is melted and
total precipitation is usually reported. Even though such gauges can operate unattended
up to a year, they should be serviced periodically to ensure collection of reliable precipi-
tation data.
(a) (c)
(b)
Figure 2.9 (a)Western Snow Conference (WSC) snow sampler. (b) Meteorological Service of Canada (MSC) snow sampler.
(c)€Snow gauges with and without Nipher shield (foreground) andTretyakov shields (background).
(b)
(a)
Figure 2.10 (a) On the basis ofWMO Double Fence Intercomparison Reference, the mean catch for (b)Wyoming snow fence was
89% of snowfall at Regina (Canada) and 87% atValdai (Russia) (Figure 1 of p. 2666 ofYang etal., 2000).

50. Snowfall and snow cover
32
Owing to the huge cost in collecting ground measurements of snow, and the harsh envir-
onment in remote areas such as mountains dominated by snowpack, where more than 70%
of snow could accumulate above the mean elevation of snow gauging stations (Gillan
et€al., 2010), we cannot rely on snow gauges or ground-based, snow course measurements
(Figure 2.9a) to estimate the snow cover area (SCA) or the amount of SWE at the regional
scale, yet seasonal snow mass variations at mid to high latitudes are the largest signals in
the changes of terrestrial water storage (Niu et€al., 2007). Information on snow cover has
been collected routinely at hydrometeorological stations, with records beginning in the late
nineteenth century at a few stations, and continuing more widely since the 1930s–1950s.
The ground is considered to be snow covered when at least half of the area visible from an
observing station has snow cover. However, it is also possible to install snow stakes or aer-
ial markers in relatively inaccessible sites by which snow depth can be observed visually
from a low-flying aircraft.
Other than being point measurements, it is well known that snow gauges, even mounted
with shields such as the Nipher shield (Figure 2.9c), suffer from under-catch problems
especially under windy conditions, where gauge totals may underestimate snowfall by
20–50 percent or more. For example, the catch ratios of the Wyoming fence to WMO-
DFIR (World Meteorological Organization-Double Fence Inter-Comparison Reference)
were 89 percent and 87 percent at Regina and Valdai, respectively (Figure 2.10a) (Yang
et€al., 2000). Yang et al. (1998, 1999) found that the mean catch of snowfall for the US 8˝
gauge at Valdai was 44€percent. For the Tretyakov and Hellmann gauges, the mean catch
of snowfall was 63–65 percent and 43–50 percent, respectively at the northern test sites
of the WMO experiment. For the WMO site set up at the Reynolds Creek Experimental
Watershed in southwest Idaho, Hanson et€al. (1999) found that an unshielded universal
recording gauge measured 24 percent less snow than was measured by the Wyoming
shielded gauge. In a mountainous watershed in NW Montana, Gillan et€al. (2010) found
greater than 25% of the basin’s SWE accumulates above the highest measurement station.
Without a wind shield, snow under-catch problems can be partly corrected by applying
adjustment coefficients to snow gauge data as a function of wind speed.
The Pan-Arctic Snowfall Reconstruction (PASR) used a land surface model of NASA
to reconstruct solid precipitation from observed snow depth and surface air temperatures
for the pan-Arctic region between 1940–1999, with the objective of correcting cold season
precipitation gauge biases (Cherry et€al., 2007). Reconstructed snowfall at test stations in
the United States and Canada is either higher or lower than gauge observations, and is con-
sistently higher than snowfall from the 40-yr European Centre for Medium-Range Weather
Forecasts (ECMWF) Re-Analysis data (ERA-40). PASR snowfall does not have a consist-
ent relationship with snowfall derived from the WMO Solid Precipitation Intercomparison
Project correction algorithms.
In Canada, snow depth and the corresponding snow-water equivalent (SWE) are meas-
ured at ground stations. Depth is routinely measured at fixed stakes, or by a ruler inserted
into the snow pack, and this depth is reported in daily weather observations at 0900 hours.
Average maximum snow depths vary from 30 to 40 centimeters on Arctic Sea ice to several
meters in maritime climates such as the mountains of western North America. The SWE
along snow courses is measured from depth and density determinations made at weekly to

51. 2.9╇Remote sensing of snowpack properties and snow-cover area
33
monthly time intervals. Such snow course networks are decreasing because of their cost
and the data may not be truly representative. Recently, Sturm et€al. (2010) explored esti-
mating SWE using snow depth data and climate classes.
From analyzing 848 stations across Canada that were reporting daily snowfall and daily
precipitation from October 2004 to February 2005, Cox (2005) found that the histogram of
the frequency of snowfall events by snow depth/SWE ratio is dominated by a spike at the
10:1 ratio, a bias caused by the 10:1 approximation being used in place of actual measure-
ments (Figure 2.11a). Recognizing the inadequacy of this 10:1 ratio, for climate stations
only equipped with a snow ruler, Mekis and Brown (2010) and Mekis and Hopkinson
(2004) proposed an alternative for more accurately estimating the SWE at a station based
on a factor called the Snow Water Equivalent Adjustment Factor (SWEAF) which can
range from 0.6 to 1.8, with SWEAF generally increasing with latitude; the province of
British Columbia tends to have a SWEAF less than 1 (Figure 2.11b).
The Canadian Meteorological Centre (CMC) Daily Snow Depth Analysis Data set con-
sists of Northern Hemisphere snow depth data obtained from surface synoptic observations,
meteorological aviation reports, and special aviation reports acquired from the WMO infor-
mation system (http://nsidc.org/data/nsidc-0447.html). In the USSR and Russian Federation,
snow depth has been measured daily as the average of three fixed stakes at hydrometeoro-
logical stations. The Historical Soviet Daily Snow Depth data begin in 1881, continuing
through 1995 at 284 stations; other parameters include snow cover percent, snow charac-
teristics, and site characterization (Armstrong, 2001). They are available at http://nsidc.org/
data/g01092.html. Snow measurements were also performed at fixed intervals over a 1–2
km transect, by taking an average snow depth for 100–200 points, and an average SWE
determined for 20 points. At some locations transects are made in fields and in forests, sep-
arately. The snow measurements were carried out at 10-day intervals and are available at
1345 sites for 1966–1990 and 200 sites through 1996 at http://nsidc.org/data/g01170.html.
2.9╇ Remote sensing of snowpack properties
and snow-cover area
Given the high albedo of snow compared to other natural surfaces, remotely sensed data
can provide useful information on the distribution of snow cover, optical properties of
snow cover, and in some instances, the snow water equivalent, even in a forest environment
(Veatch et€al., 2009). The visible band has the largest application in the snow cover extent
mapping because of snow’s high albedo to reflected (visible) sunlight that makes snow
cover easily identifiable from space, while the infrared red band has minimal application in
snow cover mapping because the snow’s surface temperature is similar to other surfaces.
Since 1966, the snow-covered area (SCA) of the Northern Hemisphere has been moni-
tored from space platforms by the US National Oceanic andAtmosphericAdministration’s
(NOAA) National Environmental Satellite Data and Information Service (NESDIS)
using Very High Resolution Radiometer (VHRR) sensors in the visible bands (0.58 to
0.68 μm, red band). These data are limited by illumination and cloud cover, and are of

52. Other documents randomly have
different content

53. Novellenerzählers in einiger Dunkelheit und nicht anders als eine
Abenteuernovelle begann.
Höret denn, Ihr lieben Herren und Damen, das Wenige, was
man vom Leben dieses herrlichen Dichters heute noch weiss, denn
[pg 16] leider ist es lange nicht so viel, als man wünschen möchte!
Aus dem Städtchen Certaldo im Elsatal gebürtig, lebte zu
Florenz ein Kaufmann namens Boccaccio. Er war ein fleissiger und
kluger, allein auch geldgieriger und leichtfertiger Mensch, welcher
zahlreiche Handelsreisen teils für fremde, teils für eigene Rechnung
unternahm, wobei er ebenso sehr für seinen Vorteil wie für sein
Vergnügen zu sorgen verstand, jedoch nach Art der Kaufleute auch
öfteren Zufällen und Glückswechseln ausgesetzt war. Längere Zeit
war er an dem grossen Bankgeschäfte des altberühmten Hauses der
Bardi beteiligt, welches auch in Paris, wie in anderen Städten, eine
Filiale besass und hohes Ansehen genoss. Diesem Pariser Hause hat
unser Kaufmann eine Zeitlang vorgestanden, und wenn er dabei sich
als einen tüchtigen Handelsmann erwies, so liess er doch in dieser
grossen und üppigen Hauptstadt auch sein Vergnügen nicht ausser
Augen.

54. Jugendbildnis BOCCACCIOS
Wenigstens sah er daselbst eines Tages eine junge und sehr
hübsche Witwe, welche [pg 17] ihm überaus wohlgefiel und deren
Gunst er sogleich zu erwerben sich bemühte. Dies tat er denn auch,
als ein gewiegter Mann, auf jede Weise, indem er sich für einen
Edelmann ausgab, was ihm bei seiner hübschen Gestalt sehr wohl

55. gelang. Er spielte den Feinen und trat nicht anders auf, als wenn er
der Sohn des vornehmsten Hauses gewesen wäre, obwohl er im
Grunde wenig mehr als ein bäuerisch gebildeter Geldwechsler war.
Bald hatte er die Augen der schönen Witwe auf sich gelenkt und sie
seinen ehrerbietigen Bitten zugänglich gemacht, und da er ihr mit
vielen Schwüren die Ehe versprach, sah er sich in kurzem am
äussersten Ziel seiner Wünsche angelangt. Zu beiderseitigem
Vergnügen erfreuten sie sich längere Zeit ihrer Liebe ohne
Hindernisse, und gewiss hätte der Florentiner noch lange nicht an
die Rückkehr nach seiner Heimat gedacht, wäre nicht infolge dieser
Liebschaft jene Witwe nach Jahresfrist mit einem hübschen Knäblein
niedergekommen. Dieses passte keineswegs in die Pläne des
leichtsinnigen Italieners, und da die Dame ausser ihrer Schönheit
keine [pg 18] Reichtümer besass, verliess er, ohne sich seiner
Schwüre mehr zu erinnern, sie und die Stadt Paris in aller Stille und
begab sich als ein lediger Mann nach Florenz zurück, wie es stets die
Art solcher Leute war, sich um eine leere Flasche und um eine
schwanger gewordene Geliebte mit keinem Blicke mehr zu
bekümmern.
Das Knäblein aber, das die arme Frau im Jahre 1313 gebar, war
Giovanni Boccaccio.
Von Schmerz und Sorge entkräftet, lebte die unglückliche Dame
nur noch wenige Jahre, und nach ihrem Tode ward Giovanni in
zartem Knabenalter nach Florenz zu seinem Vater gebracht. Dort
besuchte er eine gute Schule, erwarb sich einige Kenntnis der
lateinischen Sprache und wäre am liebsten bei den Büchern sitzen
geblieben, um sich ganz den Studien hinzugeben. Aber kaum war er
etwa dreizehn Jahr alt, so nahm ihn der Vater zu sich, lehrte ihn die

56. notwendigsten Handgriffe und Rechenkünste der Handelsleute und
übergab ihn sodann einem Geldwechsler, damit er bei diesem die
Kaufmannschaft erlernen sollte. Sechs Jahre blieb er [pg 19] denn
bei diesem Gewerbe, ohne jedoch etwas Erkleckliches zu lernen oder
gar den Handel lieb zu gewinnen. Vielmehr lief er überall hin, wo er
Verse singen oder vortragen hören konnte, und lernte viele Stücke
aus den grossen Gedichten des Dante und des Virgil auswendig,
welche ihn höchlich begeisterten und mit einer unauslöschlichen
Liebe zur Poesie erfüllten.
Am Ende dieser sechs Jahre sah jedermann deutlich, dass
Giovanni in die Handelschaft passte wie der Fisch aufs Trockene.
Dies sah auch der Vater wohl ein und beschloss daher, seinen Sohn
den Studien an Universitäten zu widmen, und zwar wählte er für ihn
das Studium des kanonischen Rechts, indem es ihm als einem
klugen Manne schien, es sei mit diesem Handwerk nicht wenig Geld
zu verdienen, wenn einer es ordentlich verstehe. Weil aber Giovanni
um diese Zeit sich eben in Neapel befand, schien es dem Vater am
wohlfeilsten, dass er dort seine Studien abmache, ohne dass er
geahnt hätte, welcherlei Kenntnisse derselbe sich dort erwerben
würde.
[pg 20] Es war nämlich Neapel zu jener Zeit gewiss die
allerüppigste Stadt in ganz Italien, zumal da gerade unter dem
Könige Robert die Einwohner eines längeren Friedens genossen,
woran sie nur schlecht gewöhnt waren. Von dem Leben bei Hofe
brauche ich wenig zu sagen, indem jedermann die Namen der sechs
Neffen des Königs, sowie seiner Schwägerin, der sogenannten
Kaiserin von Konstantinopel, und seiner Enkeltochter Johanna kennt,
welche sämtlich durch alle Welt einen bösen Leumund hatten. Vorab

57. jene Johanna führte ein überaus freches und tadelnswertes Leben,
hatte ihres Gatten Bruder zum Buhlen und nahm ihn später,
nachdem sie sich des andern durch Mord entledigt hatte, ohne
päpstlichen Dispens zum Gemahl. Auch sonst war in der Stadt,
zumal unter den Edelleuten, ein vergnügliches Schlemmen, auch
Hader und kleinere Mordtaten im Schwang, und bei Hofe war längst
zwischen echten Kindern und Bastarden weder von den Vätern, noch
von anderen mehr zu unterscheiden. An diesem Hofe, wo er noch zu
Lebzeiten des Königs von seinem jungen Landsmanne [pg 21]
Niccolo Acciajuoli eingeführt wurde, ging nun das Studentlein ab und
zu. Daselbst war mit Festen, Mahlzeiten, Ball, Tanz und
Maskenscherzen ein verschwenderisches Leben, und gewiss hat
Boccaccio niemals irgend eine üppige oder lüsterne Geschichte
erzählt, welche er nicht in Neapel viel toller und gründlicher selbst
mitangesehen hatte. Dass er auf dem Gebiete der gelehrten Studien
(das Latein ausgenommen) etwas Erhebliches geleistet oder den
Grad eines Doctoris juris canonici erlangt hätte, wird nirgends
berichtet. Statt dessen legte er damals den Grund zu seiner tiefen
Kenntnis der menschlichen Leidenschaften, da er von
hervorragenden Beispielen der Verschwendung und Habgier, des
Aberglaubens, der Wollust, der Gefrässigkeit, Mordgier,
Verschlagenheit und Eitelkeit rings umgeben war. Am gründlichsten
jedoch unterzog er sich dem Studium der Liebe, deren Leiden und
Freuden er bis zur Neige an sich selber erfuhr.
Eines Tages nämlich, um die Zeit der Ostern, vermutlich im
Jahre 1334, erblickte er [pg 22] in einer Kirche zu Neapel die Dame,
welche sein Herz zu Lust und Pein von da an jahrelang gefangen
hielt. Diese war Donna Maria, die natürliche Tochter des Königs

58. Robert, welche für eine Tochter des Grafen von Aquino galt und mit
einem angesehenen Edelmann vermählt war. Die schöne und
vornehme Dame betrachtete bald auch von ihrer Seite den hübschen
jungen Florentiner mit Teilnahme und ist eine lange Zeit, nicht ohne
Gewissensbisse und Furcht vor ihrem Eheherrn, seine Geliebte
gewesen. So genoss, wie in der schönsten Abenteuernovelle, der
Bastard eines kleinen Kaufmanns die Tochter eines grossen Königs.
Über alledem liess Boccaccio das kanonische Recht unbehelligt
in den Pergamentrollen schlummern und vom Lehrstuhl ertönen. Er
trieb nach seiner Neigung Latein und Astrologie, im übrigen wandte
er sich der heiteren Seite des Lebens zu und ward nach Kräften
seiner Jugend froh. Er verfasste in diesen Jahren, zumeist für seine
Geliebte, eine unglaubliche Menge von Gedichten und mehrere
Romane, von welchen [pg 23] heute niemand mehr redet. In diesen
legte er seiner Dame den Namen Fiammetta bei, und noch manche
Jahre später hat er in wehmütiger Liebeserinnerung diesen Namen
einer von den Damen des Dekameron gegeben. Ohne Zweifel ist
jene Zeit die heiterste und glücklichste in seinem Leben gewesen.
Allein wie wir sehen, dass auch den goldensten Tagen zu früh die
Sonne sinkt, so nahm auch diese Lust zu ihrer Zeit ein Ende.
Im Jahre 1341 befahl der Vater seinem Sohne, nach Florenz
zurückzukehren, und nach längerem Zögern machte dieser sich
unmutig auf den Heimweg. Der Alte, für den Giovanni ohnehin keine
allzu starke Zärtlichkeit empfand, hatte inzwischen auch noch eine
gewisse Monna Bice Bostichi geheiratet, worüber der heimkehrende
Sohn nicht eben erfreut war. Es geschahen jedoch weit schlimmere
und wichtigere Dinge, über welchen er diese kleineren Sorgen
vergass. Es war die Zeit, in welcher der in Florenz so übel

59. beleumdete Herr Gautier von Brienne, genannt Herzog von Athen,
sich für eine kurze Zeit zum Tyrannen der Stadt emporschwang. [pg
24] Dieser war ein frecher Abenteurer und hatte im Solde der
Republik gegen Pisa gedient, warf sich nun aber mit Hilfe des
niedrigsten Pöbels zum Herrscher auf und schlürfte die Monate
seiner Herrlichkeit zügellos wie ein Trunkener den letzten Becher. Die
Stadt und das ganze Staatswesen drohten in Trümmer zu gehen.
Boccaccio, ein unbestechlicher Republikaner, hat das Schicksal
des Herzogs von Athen, der mit Schimpf von der Bürgerschaft
vertrieben wurde, in einer Abhandlung beschrieben. Nun schienen
ihm allmählich die Zustände in Florenz und im väterlichen Hause so
wenig erträglich, dass er schon im Jahre 1344 von neuem nach
Neapel ging. Die Rechtsgelehrtheit hatte er schon früher
aufgegeben. Und so genau er auch im Dekameron die Pest in
Florenz geschildert hat, ist er zurzeit derselben doch nicht daselbst
gewesen, sondern in Neapel, wo freilich der schwarze Tod nicht
weniger grauenhaft wütete. Es starb damals auch seine Geliebte
Maria, und er widmete ihrem Tode zwar einige trauernde Verse,
jedoch war seine [pg 25] ursprünglich so heftige Leidenschaft mit
den Jahren erloschen. Es scheint ausserdem, als habe Donna Maria
ihn schon früher wieder fahren lassen, obwohl er in seiner Erzählung
„Fiammetta“ das Gegenteil darstellt. Nicht lange darauf starb auch
sein Vater, und er musste wieder nach Florenz zurückkehren.
Von da an erblicken wir sein Bild verändert; sein Leben verlief
ohne heftige Erschütterungen, und er alterte als ein tüchtiger und
angesehener Bürger. Im Alter von ungefähr 40 Jahren schrieb er sein
unsterbliches Dekameron, und man könnte glauben, er habe alle
seine Schalkhaftigkeit und fröhlich lachende Untugend darin liegen

60. lassen. Nur noch einmal widerfuhr ihm eine bittere Liebesgeschichte.
Er verliebte sich heftig in eine vornehme Witwe, welche ihm aber
einen bösen Possen spielte. Nämlich sie stellte sich, als wäre sie
geneigt, die Wünsche des Dichters zu erfüllen, und benutzte alsdann
die erste Gelegenheit, ihm eine Nase zu drehen und ihn unter dem
Hohngelächter all ihrer Bekannten und Freunde kläglich
heimzuschicken. Das war Boccaccios letzte Liebe.
[pg 26] Im übrigen, da der Vater ihm eine kleine Erbschaft
hinterlassen hatte, lebte er als ein stillgewordener Mann und
widmete sich allerlei gelehrten Studien. Den Griechen Leontius
Pilatus hatte er, um seine Sprache zu lernen, über zwei Jahre lang
bei sich im Hause. Öfters übernahm er im Dienste der Stadt
politische Aufträge und Ambassaden, unter anderem besuchte er
dreimal als Gesandter den Papsthof zu Avignon. Mit grossem Eifer
forschte er dem Leben und den Schriften des Dante nach, den er
ungemein verehrte. Mit dem etwas älteren Petrarca, welcher damals
von sich selber und von jedermann für den grössten lebenden
Dichter gehalten wurde, pflegte er eine edle und herzliche
Freundschaft und war untröstlich, als dieser im Jahre 1374 starb.
Aber das Leben dieses merkwürdigen Mannes, dessen Anfang
ein Abenteuer und dessen erste Hälfte ein Hymnus der Liebe zu sein
scheinen, verwandelte sich zum Schlusse noch in eine fromme
Posse. Noch als ein rüstiger Mann hatte er das Dekameron
geschrieben, welches bald auf schalkhafte, bald [pg 27] auf
leidenschaftliche Art dem Dienste schöner Frauen huldigt und über
Mönche und Priester unerschöpflichen Hohn ergiesst. Nicht gar viel
später aber gelang es einem schwindelhaften Mönche, namens Ciani,
ihn zu bekehren, und zwar vermittelst einer nicht einmal sehr

61. durchtriebenen Bauernfängerei, und von da an hörte man ihn seine
schönsten Werke nie anders denn als verwerfliche Jugendsünden
und Verirrungen bezeichnen. Noch viel schlimmer aber und
lächerlicher ist es, dass der vormalige Schalk und Weiberfreund in
seinen älteren Tagen zu einem argen Frauenverächter ward und ein
Buch mit dem Titel Corbaccio geschrieben hat, in welchem man,
wenn man Lust hat, hunderte von schimpflichen, grausamen,
hasserfüllten und anklagenden Reden über die Weiber finden
kann — dazu in einer Redeweise, welche an Unflätigkeit auch die
kühnsten Stellen seiner früheren Werke zehnmal übertrifft. Das sollte
seine Rache an jener grausamen Witwe sein; allein der Dichter tat
damit, wie wir es oft sich ereignen sehen, nur einen Schnitt ins
eigene Fleisch.
[pg 28] Eine späte Ehre ward ihm zuteil, indem er nach
mannigfachen Studien und Reisen im Jahre 1373 zum öffentlichen
Ausleger der göttlichen Komödie des Dante zu Florenz ernannt
wurde, wofür er jährlich hundert Goldgulden bezog. Diese
Vorlesungen hielt er unter grossem Zulaufe in der Kirche Santo
Stefano bis kurz vor seinem Tode. Er starb am 21. Dezember 1375,
zweiundsechzig Jahre alt, und wurde ehrenvoll bestattet. Die Liebe
zu der grossen Dichtung des Dante verlieh seinen späteren Tagen,
trotz des bösen Corbaccio, noch eine gewisse ehrwürdige Glorie. Für
die nachfolgenden Jahrhunderte aber ist er wieder der
Geschichtenerzähler mit der Schelmenmiene geworden, und dem
heutigen Geschlecht ist an einem einzigen Witz aus einer seiner
Novellen mehr gelegen als an der ganzen Gelehrsamkeit und
Ehrbarkeit seines ehrenvollen Alters.

62. [pg 29]

63. Über die Dichtergrösse des Boccaccio, welchen man gerne den
dritten unter den grossen italienischen Poeten nennt, steht in vielen
Büchern viel geschrieben, was alles zu wiederholen nicht vonnöten
ist. Er war unter denen, welche jemals kunstgerechte Novellen
verfasst haben, nicht nur der Erste, sondern indem er diese
scheinbar geringe Kunst früher als irgend ein anderer betrieben, ja
eigentlich erfunden hat, übte er sie sogleich mit einer solchen
Vollendung aus, dass er von keinem seiner unzähligen Nachfolger
übertroffen oder auch nur erreicht werden konnte. Nicht weniger
gross ist aber sein Verdienst um die italienische Sprache, welche er
nicht etwa nur verschönert und ausgeschmückt, sondern in
gewissem Sinne eigentlich neu geschaffen hat. Denn obwohl schon
lange vor ihm der Florentiner Dante das grösste und schönste
italienische Gedicht verfasst hat, war doch das Gebiet der Erzählung
und die Prosasprache überhaupt noch von keinem mit [pg 30]
einiger Kunst gepflegt worden, indem die Gelehrten häufig lateinisch
geschrieben hatten. Die mündliche Sprache des Volks, welche in
Florenz mit besonderer Schönheit und Reinheit gebraucht wird, hat

64. Boccaccio als der Erste in seinen Erzählungen mit ihrer natürlichen
Anmut und Mannigfaltigkeit verwendet und zugleich mit so grosser
Kunst gepflegt, dass sie in seinen Händen sich in etwas ganz neues
und herrliches verwandelte.
In den Büchern des Dekameron zu lesen, ist für einen, welcher
seine Lust an einer schönen und lebendigen Sprache hat, nicht
anders als ein Wandeln unter blühenden Bäumen und als ein Baden
in einem reinen Gewässer. Die Worte klingen so frisch, als wären sie
soeben erschaffen und vorher noch in keinem Munde gewesen; in
jedem kleinen Satze springen klare, lachende Quellen auf, und die
Sätze tanzen bald leicht und zierlich, bald rollen sie tönend und
wohllaut hin. Vielen will es scheinen, es habe Boccaccio zuweilen
seiner Sprache Gewalt angetan, und es mag ein wenig Wahrheit
daran sein. Während er die Worte aus der Sprache des [pg 31]
Volkes von Gassen und Märkten nahm, bildete er hinwieder den Bau
seiner Perioden vornehmlich nach dem Muster der römischen Redner
und Autoren, zumal des Cicero, den er ungemein verehrte.
Dadurch mag vielen, auch wenn sie der heutigen italienischen
Sprache mächtig sind, das Lesen des Dekameron ein schweres und
mühsames Werk erscheinen. Allein es ist nicht nur der Anfang dieses
Buches der langen Perioden wegen schwieriger zu lesen als die
Folge, sondern es pflegen ohnehin nach einigen Versuchen die
meisten an dieser Sprache ein solches Gefallen zu finden, dass sie
schnell einige Übung darin erlangen. Und vornehmlich darf
derjenige, welchem etwa das Lesen des Dante zu schwerster Mühsal
gereichte, so dass er ermüdet davon abliess, durchaus nicht
fürchten, hier auf dieselben Schwierigkeiten zu stossen. Kurzum, wer
einigermassen italienisch versteht, möge sich nicht scheuen, das

65. Dekameron im originalen Texte zu lesen.*
Sobald er nur einige
Übung [pg 32] erlangt hat, wird ihm über den Seiten dieses Buches
sein, als höre er Vögel zwitschern, Kinder lachen und Wasser
rauschen, eine solche innere Kraft und freudige Lebensfülle ist in
dieser Sprache verborgen.
Was das Dekameron als Dichtung anbelangt, so ist es überaus
merkwürdig zu sehen, wie alle Kräfte und Vorzüge des Dichters,
welcher ja auch eine nicht geringe Zahl von anderen Werken
geschrieben hat, in diesem einen Hauptwerke sich schön und
harmonisch vereinigen. Die früheren, allmeist in Neapel
entstandenen Dichtungen des Meisters handeln fast ohne eine
einzige Ausnahme von der Liebe, und die Erzählung „Fiammetta“ ist
bei weitem die schönste unter ihnen. Jedoch weiss in allen diesen
Dichtungen Boccaccio nichts anderes darzustellen als seine eigenen
Gefühle und Liebesgedanken, [pg 33] ohne genügende
Mannigfaltigkeit, und die Verse, soweit es sich um solche handelt,
sind mit grossem Fleisse, aber geringer Erfindungskraft dem Muster
des Petrarca nachgeformt, wie denn stets die jungen Poeten solche
Berühmtere nachzuahmen bestrebt waren. Von diesen Dichtungen
erwecken mehrere eine Ahnung von seinem späteren Werke, als
habe die Idee desselben ihm schon längere Jahre am Herzen
gelegen.

66. BOCCACCIOS Handschrift
Aber wie ein frischer und tüchtiger Mann erst in den Jahren der
völligen Reife die schwere Kunst des Lebens lernt, die darin besteht,
dass der einzelne Mensch seine Schicksale und Gefühle gleich der
Welle im Meer ansehen und mit heiterer Bescheidenheit im
grösseren Leben der Gesamtheit verbergen kann, so besann sich
auch dieser Boccaccio erst in späteren Jahren, als schon die
Leidenschaft seiner Jugendzeit verglommen war, auf alle seine
Kräfte. Was er von Kind auf, aus seiner Bastardkindschaft her, und
alsdann in Florenz und Neapel und auf manchen Reisen erfahren
hatte, wurde nun zu plötzlicher Klarheit erhoben und im stillen
entbunden. Nicht [pg 34] weniger die Leiden und die Wollust der
Frauenliebe als der Zauber des Reisens und Schauens, die Erlebnisse
und Sitten der Studenten ebenso wie die Sorgen und Plagen der
Kaufleute, die Gebräuche, Tugenden und Laster derer, die bei Hofe
und die in der Wechselbank und die auf den Märkten oder zu Schiffe

67. leben und ihr Brot zu erwerben suchen, die Eigenschaften der
Narren wie der Weisen, die Lebensart der Priester, der Richter, der
Soldaten, der Seefahrer, der Frauen, der Dirnen sowie alles Ernste,
Schöne, Seltsame, Lächerliche und Traurige des menschlichen
Lebens, soweit nur jemals ein Mensch es erfahren und beobachtet
hat — dieses alles zog er nun aus seinem Gedächtnisse hervor.
Gewisslich sind von den hundert Erzählungen des Buches
Dekameron nur sehr wenige von Boccaccio selbst erfunden worden.
Vielmehr hatte er die einen erzählen hören, die anderen selbst erlebt
oder sich zutragen sehen, andere auch aus alten Sagen und Liedern
und Fabeln genommen. Nur ein Tor möchte wünschen, er hätte sie
alle selbst sich [pg 35] ausgedacht. Im Gegenteil ist es einer der
grössten Vorzüge des Dekameron, dass es gleich einem Speicher
oder Juwelenschrank die Erfahrungen und Schicksale unzähliger
Menschen und Zeiten in sich beschlossen hält. Viele von den
Geschichten kamen aus dem Morgenlande, aus Griechenland und
aus Frankreich, Spanien und Germanien her, viele sind schon sehr alt
gewesen, andere wieder erst von gestern. Dass aber ein einzelner
Mann diese zahllosen kleinen Stücke in seinem Gedächtnis
gesammelt, alsdann geordnet und verbessert und am Ende zu einem
grossen, wundervollen Ganzen zusammengesetzt hat, dazu in einer
von ihm selbst geschaffenen, vollkommenen Sprache — und das
Ganze so ebenmässig, rein und klar und in sich selber einig, als wäre
alles am selben Tag und aus demselben Geist entstanden — dieses
ist, so oft man es auch betrachte, ein fast unbegreifliches Wunder.
Begebenheiten und Lehren, Spässe und weise Erfahrungen, die eine
uralt, die andere frisch von der Gasse, die eine von Hofe, die andre
aus dem Bettelvolk, die eine arabischen, die andre deutschen, [pg

68. 36] die dritte französischen Ursprungs, lustige und klägliche, edle
und gemeine, diese alle zusammen zu einem einzigen prächtigen
Werk vereinigt, aneinander gefügt und wie die Steine eines
Geschmeides jede die Nachbarin hebend und verzierend, und
dennoch jede einzelne bis in die geringsten Teile mit aller Kunst und
Sorgfalt ausgebaut und zur Vollkommenheit gebracht! Wahrlich,
wenn Boccaccio in seinem Leben eine grosse Torheit und Sünde
begangen hat, so war es, als er sein unsterbliches Werk selber als
eine müssige und leichtfertige Jugendarbeit und Verirrung
verleumdete.
Allerdings genoss er zu seinen Lebzeiten den meisten Ruhm
nicht um der Novellen, sondern um seiner gelehrten Werke willen,
von welchen heute nur noch die Vita di Dante einigen Wert hat.
Dennoch zählte er zu den unterrichtetsten Männern seiner Zeit, und
indem er einen schönen lateinischen Stil schrieb, sich sehr um die
alten Autoren bemühte und auch die damals nur wenig gepflegte
Kenntnis des Griechischen auszubreiten bestrebt war, hat er ebenso
wie Petrarca einen ruhmvollen [pg 37] Anteil an der Begründung des
italienischen rinascimento.
Von der Beschaffenheit, Einrichtung und Konstruktion des
Dekameron will ich später sprechen. Über das Schicksal desselben ist
wenig zu sagen, als dass es — unendlichen Anklagen und
Verleumdungen zum Trotze — schon nach kurzer Zeit über mehrere
Länder verbreitet war, auch seither in vielen Übersetzungen und
hunderten von Ausgaben immer wieder gedruckt worden ist.
Unglücklicherweise ist keine Handschrift der Novellen von der
eigenen Hand des Boccaccio erhalten geblieben, und lange Zeit
wurde mit dem Texte so nach Willkür umgesprungen, dass es erst

69. später fleissigen Gelehrten gelang, ihn so ziemlich wieder auf den
status quo ante zu bringen.
Das Dekameron hat häufige Wiedergeburten im Geiste anderer
grosser Dichter und Künstler gefeiert. Gleichwie in dem Schauspiel
„Nathan der Weise“ die dritte Novelle, von den drei Ringen, eine
neue Gestalt annahm und wieder Tausende erfreute, so haben
früher und später viele andere, vor [pg 38] allem Shakespeare, aus
dem Schatze des Florentiners geschöpft, dessen Spuren in
zahlreichen Dichtungen aller Völker zu finden sind. Nicht weniger
haben die Zeichner und Maler sich an ihm vergnügt und viele seiner
Novellen in Bildern dargestellt; und noch im Jahre 1849 hat der
britische Malermeister Millais aus der Novelle vom Basilikumtopf (Tag
4, Novelle 5) eine Szene in einem berühmten Gemälde abgebildet.
Der vielen anstössigen Stellen wegen hat man schon früher des
öfteren sogenannte verbesserte und purgierte Ausgaben
veranstaltet. Was in solchen Fällen, zumeist von geistlichen Herren,
am Text verballhornt und geschändet worden ist, lässt sich leicht
denken. Dabei kümmerte man sich übrigens wenig um die derben
und heiklen Stellen, sondern vor allem um jene, in welchen
Boccaccio der Geistlichkeit unliebsame Wahrheiten gesagt hat.
Einmal, ums Jahr 1570, wurden zu Florenz vier Herren ernannt zu
der Aufgabe, das Dekameron endgültig von allen gegen die
Satzungen der Kirche verstossenden Stellen zu säubern. Da wurden,
wo immer es nötig [pg 39] schien, aus den Mönchen Bürger und
Ritter, aus den Nonnen Edeldamen gemacht, zwei von den Novellen
wurden zu einem mysteriösen Unsinn verbessert, und als nach
langer Mühe die Ausgabe vollendet war, zeigte es sich, dass den
Herren eine der heitersten Geschichten durch die Finger geschlüpft

70. war, und jenes Dekameron hatte statt hundert nur neunundneunzig
Novellen. Ausserdem ist das Buch häufige Male „für die Jugend“
ediert worden und wird es in Italien „per giovani modesti“ heute
noch.
Besonders schlimm erging es ihm mehr als hundert Jahre nach
seines Verfassers Tod, zur Zeit des wohlbekannten oder
übelbekannten Savonarola. Dieser wütende und vermutlich
geisteskranke Mönch, welcher nach Kräften dazu beitrug, Florenz
und Italien dem Untergang näher zu bringen, hat ausser einer
Menge von anderen schönen Dingen auch sehr viele Exemplare des
Dekameron öffentlich verbrennen lassen.
Wo jedoch eine kräftige Quelle aus der Erde gebrochen ist, hat
das Verbauen und das Exorzieren niemals viel geholfen, und es [pg
40] ist schwerer, etwas geistig Lebendiges zu ertöten, als etwas
Totes wieder zum Leben zu bringen. So hat denn auch Boccaccio
manche Zeitgenossen und Nachfolger gehabt, deren erloschenen
Ruhm die Gelehrten mit unsäglichen Mühen bis auf heute herüber
geschleppt haben, indessen er selber inmitten aller Keulenschläge
am Leben blieb und heute noch den gleichen Glanz und Zauber hat
wie seinerzeit.
Indem ich dieses schreibe, träumt mir von einem
Cypressenbaum am Hügelabhang zwischen Vincigliata und
Settignano, wo ich vor Zeiten zum erstenmal, im Grase liegend, das
köstliche Buch genoss. Es lief ein lauer Wind talab, mit Blütenduft
von Limonen und Mandeln beladen, es lag ein süsses Licht über
Florenz und allen Bergen, und es sang aus einem fernen Garten eine
welsche Laute herüber, allein ich sah es nicht und hörte es nicht; ein

71. süsserer Duft und ein viel köstlicherer Klang stieg mir aus den
gelben Blättern des alten Buches zu Häupten.
[*] Wodurch aber niemand von der Lektüre einer Übersetzung abgeschreckt
werden soll! Vor den zahlreichen verkürzten und verstümmelten
Ausgaben aber sei dringend gewarnt! Das Dekameron muss notwendig
unverkürzt gelesen werden. Zur Zeit ist die einzige vollständige, übrigens
ganz vortreffliche deutsche Übersetzung die von Schaum, deren neue
Ausgabe in drei Bänden 1903 im Insel-Verlag in Leipzig erschienen ist.
[pg 41]

72. Das Buch Dekameron ist auf eine solche Art eingerichtet, dass seine
hundert Novellen an zehn Tagen von zehn jungen und edlen Leuten
erzählt werden, und darunter sind sieben Mädchen und drei
Jünglinge. Auf diese Weise kommt daher jede Novelle nicht aus
unbestimmter Ferne, sondern frisch aus dem Munde eines jungen
Erzählenden zu uns her geklungen. Und überdies ist also diese Zahl
von hundert Geschichten und Schwänken von einer lebendigen
Erzählung umflochten, hat auch jeder von den zehn Tagen seine
besondere Art und Färbung.
Die Erfindung des Boccaccio ist diese: Zur Zeit des schwarzen
Todes, welcher die Stadt Florenz im Jahre 1348 heimsuchte, waren
in dieser Stadt alle früheren Ordnungen und Gewohnheiten
vollkommen aufgelöst. Es lagen in den Häusern, auf den Treppen
und vor den Türen, ja in allen Gassen da und dort teils Tote, teils
Todkranke umher, und die Gefahr der Ansteckung war so gross, [pg
42] dass Eltern und Kinder, Brüder und Schwestern einander flohen
und die Erkrankten einsam und ohne Pflege dahinsterben liessen,
welche Zustände Herr Boccaccio im Beginn seines Buches mit der

73. grössten Genauigkeit und Sichtbarkeit uns schildert. Bei solcher
grausamen Verwirrung und Schrecknis trafen sich eines Morgens
sieben junge Damen in der herrlichen Kirche Santa Maria Novella,
welche zwar damals noch der berühmten Wandmalereien des
Ghirlandajo entbehrte, aber auch schon zu jener Zeit eine der
schönsten Kirchen von Florenz gewesen ist.
Diese Sieben, da sie sich unter gemeldeten Umständen nicht
allein in beständiger Todesgefahr, sondern auch jeglicher Freude und
Lustbarkeit durchaus beraubt sahen, beschlossen auf den Rat der
Pampinea, welche die Älteste von ihnen war, sich in Gesellschaft auf
das Land zu begeben und dort einige Zeit in Ruhe und heiteren
Gesprächen zu verweilen, wobei sie die gegenwärtige Trauer und
Bangnis ein wenig vergessen könnten. Und siehe, während sie noch
über einige etwa passende Begleiter und über den [pg 43] Ort ihres
Aufenthaltes beratschlagten, traten drei edle Jünglinge in dieselbe
Kirche, von welchen jeder in eine unter diesen Damen verliebt war.
Ihnen eröffnete Pampinea, welche mit einem derselben verwandt
war, ihr Vorhaben und forderte sie auf, als Führer und Kavaliere mit
ihnen zu kommen; und sogleich waren die jungen Herren, wie man
sich denken kann, von Herzen gern dazu bereit. Auch diejenigen von
den Mädchen, welche anfänglich einige Scheu gehabt hatten,
freuten sich nun darüber, denn es war sogleich vereinbart worden,
dass Sitte und Ehrbarkeit in jeder Weise gewahrt blieben.
Also begab sich diese hübsche und fröhliche Gesellschaft edler
junger Leute aus der Stadt und hatte die Wahl des Aufenthaltes
zwischen gar vielen Landsitzen, denn infolge der Pest stand auch auf
dem Lande alles leer und verlassen. Nur zwei Meilen weit vor den
Toren fand sie denn auch auf einem Hügel gelegen einen Palast in

74. der schönsten Umgebung, von Blumenmatten, wohlriechenden
Gebüschen und Bäumen und fliessendem Wasser umkränzt, mit
Garten, Hof und Brunnen; [pg 44] auch waren Säle, Kammern und
Keller wohl versehen. Hier liessen sie sich mit grossem Vergnügen
samt ihrer mitgebrachten Dienerschaft nieder, und der Jüngling
Dioneus war der Erste, welcher allen vorschlug, die Sorgen in der
Stadt dahinten zu lassen und sich, so lange es ihnen gefiele, heitere
Tage zu machen.
Alsbald schien es ihnen, auf den Rat der Pampinea, gut, dass an
jedem Tage einer aus der Gesellschaft zum Könige ernannt würde,
welcher die übrigen samt der Dienerschaft zu beherrschen und alles
zum Wohlbehagen und zu guter Unterhaltung dienliche anzuordnen
habe. Und es wurde für diesen ersten Tag als Königin die Pampinea
gewählt. Diese wieder bestimmte einen aus der Dienerschaft zum
Seneschall, andere zum Aufwarten, zum Kochen und zu sonstigen
Diensten, wie in einem wohleingerichteten Hofstaat. Hierauf begab
sich jedermann, wohin er wollte, und betrachtete die schönen
Gärten, Säle, Lauben, Wiesen, Brunnen und Quellen, bis es Zeit zu
Tische war. Die Tafel war voll von trefflichen Speisen und ganz mit
Ginsterblüten [pg 45] bestreut, es fehlte nicht an blanken Gläsern
noch an Handwasser und weissem Linnengedeck. Nach der Mahlzeit
aber suchte jeder sich einen Ort zur Ruhe und schlief eine Weile, bis
die Königin aufs neue alle zusammen berief und auf einen schattigen
Rasenanger führte. Nachdem sie ein wenig getanzt und gesungen
hatten, standen wohl Schach- und Damenbretter und genug andere
Spiele bereit, allein der Königin und auch allen anderen schien es
unterhaltsamer und erfreulicher, dass jeder eine Geschichte, die er
wisse, vortrage. So erzählte also jeder eine nach seinem Belieben,

75. und am Ende der zehn Novellen war es Abend geworden, und sie
beschlossen diesen ersten Tag damit, dass Emilia eine schöne
Canzone sang, während Lauretta einen Tanz dazu aufführte, von
Musikinstrumenten begleitet.
Darauf übertrug die Königin ihr Regiment an Philomena, und
diese hübsche und kluge junge Dame ordnete an, es sollten am Tage
ihrer Regierung solche Geschichten erzählt werden, in welchen einer
aus grossem Unheil unerwartet doch noch entrinnt und ein
glückliches [pg 46] Ziel erreicht. In einer ähnlichen Weise verliefen
alle zehn Tage und zwar in dieser Ordnung:
Erster Tag: Unter der Königin Pampinea erzählt ein jeder, was
ihm beliebt und einfällt.
Zweiter Tag: Unter der Königin Philomena werden die Schicksale
solcher vorgetragen, welche unerwartet aus grossem Unheil zu
neuem Glücke hervorgingen.
Dritter Tag: Unter der Königin Neiphile spricht man davon, wie
einer durch Scharfsinn ein ersehntes Ziel erreichte oder etwas
Verlorenes zurück gewann.
Vierter Tag: Unter dem König Philostratus redet man von
Verliebten, deren Liebe ein tragisches Ende nahm.
Fünfter Tag: Unter der Königin Fiammetta werden Geschichten
erzählt, in welchen Liebende nach allerlei Hindernissen und Unfällen
doch noch zum Glücke gelangen.
Sechster Tag: Unter der Königin Elisa ist die Rede von schnellen
und witzigen Aussprüchen, Antworten und Neckereien.
Siebenter Tag: Unter dem Könige Dioneus [pg 47] werden
Streiche erzählt, welche Ehemännern von ihren Weibern gespielt
wurden.

76. Achter Tag: Unter der Königin Lauretta spricht man von
Streichen und Possen, welche so wohl Eheleute wie beliebige andere
Personen einander gespielt haben.
Neunter Tag: Unter der Königin Emilia trägt ein jeder vor, was
ihm behagt.
Zehnter Tag: Unter dem König Pamphilus ist die Rede
ausschliesslich von Taten des Edelmutes und der Hochherzigkeit.
Ausserdem dass jede dieser hundert Novellen durch die Art und
Person dessen, der sie erzählt, einen besonderen Ton und eine
eigene Art von Anmut gewinnt, sind die Erzählungen unter einander
noch auf vielfache und zierliche Weise verbunden. Denn indem
zumeist über die soeben vorgetragene Novelle sich ein kürzeres oder
längeres Gespräch in der Gesellschaft entspinnt, knüpft alsdann der
nachfolgende Erzähler fast immer an dieselbe an und bringt eine
Historie zum Vortrag, welche das angeschlagene Thema von einer
neuen Seite beleuchtet und deutlicher macht, jedoch ohne dass
hierdurch jemals [pg 48] der Anschein der Eintönigkeit erweckt
würde. Denn bei mancher Ähnlichkeit des Themas ist dennoch jede
von diesen Novellen von allen anderen scharf unterschieden, und es
gibt keine zwei darunter, die man so leicht mit einander verwechseln
könnte. Nächstdem aber ist jeder Schatten von Gleichförmigkeit
auch noch durch andere feine Künste vermieden worden, indem
z. B. Dioneus, welcher der Hauptspassvogel der Gesellschaft ist,
stets mit völlig unerwarteten neuen Einfällen dazwischen tritt, auch
allerlei Anspielungen und Neckereien zwischen den Erzählenden
vorfallen.

77. DIE KIRCHE SAN STEFANO IN FLORENZ
Dazu kommt, dass jeder von den zehn Tagen seine eigene
Geschichte hat, mit allerlei kleinen Zwischenfällen, so dass wir

78. ausser den täglich erzählten zehn Geschichten auch die übrigen
Beschäftigungen und Lustbarkeiten der Gesellschaft erfahren.
Daneben ist der Ort, an welchem sie sich aufhält und welchen sie
zwischenein auch wechselt, mit Hainen, Teichen, Bächen, Blumen,
Wild und Fischen stets auf das Anmutigste und Lebhafteste
geschildert, wodurch im Gemüt des Lesenden teils ein fortwährendes
Behagen, [pg 49] teils auch eine milde, angenehme Sehnsucht nach
solchen auserlesen köstlichen Gegenden erregt wird. Denn der
Dichter hat dieselben zwar einigen Örtern ähnlich gebildet, welche
man in der Nähe von Florenz und namentlich im Tal des Mugnone
antrifft, allein dennoch hat er sie in solcher Art geschmückt und
dargestellt, wie es nur ein wahrer Künstler vermag, so dass sie alle
etwas Verschöntes und wahrhaft Paradiesisches an sich tragen.
So ist denn unter den zahlreichen Büchern, in welchen ein
Einzelner viele verstreute Erzählungen gesammelt hat, in aller Welt
kein einziges, welches irgendwie an Schönheit und Kunst dem
Dekameron vergleichbar wäre. Der es seinerzeit geschrieben hat, tat
es zum Trost der unglücklichen Liebenden und vornehmlich zur
Erfreuung der Frauen, welchen denn auch das ganze Werk in einem
vortrefflichen Prologe zugeeignet ist.
[pg 50]

79. Man hört gar häufig sagen, das Dekameron sei ein unanständiges
und verwerfliches Buch. Und diejenigen, welche dies sagen und
gerne predigen, sagen es zum Teil nach dem blossen Hörensagen,
zum Teil aber kennen sie das verwerfliche Buch sehr gut und lesen
es in der Stille häufig. Was nun die Unanständigkeit betrifft, welche
stets in Büchern viel heftiger als im Leben bekämpft wird, so kann
und mag ich sie keineswegs leugnen. Als ich einstmals in demselben
Tal des Mugnone, wo es seinen Schauplatz hat, das Dekameron in
einem schönen Frühlingsmonat ganz durchlas, pflegte ich der
Wärme wegen frische Limonen dazu zu speisen. Und nun hatte ich
die Gewohnheit, dass ich bei jeder Novelle, die mir unanständig
erschien, einen Limonenkern in meine Tasche steckte, und als ich
ganz zu Ende gelesen hatte, zählte ich neununddreissig solche
Kerne. Hiernach wäre denn etwas mehr als ein Dritteil des
Dekameron von unanständiger Beschaffenheit.
[pg 51] Obwohl ich glaube, dass gerade diese neununddreissig
Novellen zu den schönsten und ergötzlichsten gehören, will ich doch
den Inhalt derselben nicht zu verteidigen unternehmen. Es ist eine

80. Ordnung der Natur, dass die Menschen gleich anderen lebenden
Geschöpfen ihre Art nicht (wie manche Pflanzen tun) sich durch
Knollen fortsetzen, sondern in zwei Geschlechter zerfallen, woraus
beiden Teilen ebenso wohl viel Vergnügen als häufiger Kummer
entsteht. Und es ist eine andere Ordnung (diese jedoch nicht von
der Natur), dass die meisten wohlgesitteten Menschen diese
natürlichen Dinge zwar billigen und ihren Gesetzen folgen, aber
durchaus nicht davon gesprochen wissen wollen. Und auch noch
viele, welche mündlich nicht selten davon zu sprechen und zu hören
pflegen, sehen es doch in gedruckten Büchern nicht gerne.
Unser Novellenbuch hat das Bestreben und die Eigenschaft, ein
Spiegel des wirklichen Lebens zu sein. Wie ich für sicher glaube, hat
wohl an der Hälfte aller wichtigen menschlichen Begebnisse,
Leidenschaften, [pg 52] Schicksale, Freuden und Leiden das
Verhältnis der Geschlechter grossen Anteil. Wenn nun das
Geschichtenbuch des Boccaccio nur zu einem Dritteil von solchen
Stoffen handelt, ist es also doch immer noch um ein Erkleckliches
anständiger und schamhafter als das Leben selber. Ausserdem sind
diese Stoffe von den Erzählern teils so zart und mit guten
Nutzanwendungen vorgetragen, teils so fein und erheiternd mit Witz
und Wortspiel verziert, teils auch so burlesk und drollig, dass ihnen
die natürliche Gemeinheit zum guten Teil genommen ist und dass sie
bei gesunden und vernünftigen Lesern gewiss keinen Schaden
anzurichten vermögen. Dazu kommt, dass neben diesen anderen so
viele Geschichten voll Reinheit und Edelsinn stehen, ja auch unter
denen, welche ausschliesslich von der Liebe handeln, finden sich
nicht wenige Beispiele von seltener Keuschheit, Treue und
Ehrbarkeit. Überdies war der Meister ehrlich genug, jeder Geschichte

81. ihren kurzen Inhalt in Überschriften voranzustellen, so dass, wer
gewisse Dinge verabscheut, die davon handelnden Novellen
ungelesen überschlagen kann.
[pg 53] Ein besonderer Vorwurf wird ungerechter Weise dem
Dekameron darüber gemacht, dass die einzelnen Geschichten von
Erzählern beiderlei Geschlechts berichtet werden und dass die
jungen Damen nicht nur manche derbe Posse mit anhören, sondern
auch selbst solche erzählen. Mir ist zwar nicht bekannt, weshalb die
Frauen so viel mehr als die Männer vor jenen Dingen Scheu haben
sollten, auch kann man jeden Tag sehen, dass dem in Wirklichkeit
nicht so ist; dennoch hat auch hierfür der Meister sich fein und
deutlich entschuldigt, indem fast jede Novelle im Beginn oder am
Schlusse einleuchtend erklärt, warum und in welcher Absicht sie
erzählt sei. Die Einführung der Erzählungen heiklen Inhalts hat
Boccaccio auf eine ungemein heitere und kluge Weise gegeben.
Unter den drei Jünglingen der Gesellschaft befindet sich einer
namens Dioneus, ein Witzemacher, Spötter und Schalk vom reinsten
Wasser. Dieser nun ist der erste, welcher am ersten Tage es wagt,
eine sogenannte saftige Geschichte vorzutragen, und er behält sich
das Recht vor, ohne Zwang jedesmal gerade das zu [pg 54]
erzählen, was er im Augenblick besonders unterhaltend fände.
Dieser Dioneus fährt denn auch stets, ohne sich sonderlich an das
vorgeschlagene Thema zu halten, in der begonnenen Art fort, und
unter den zehn von ihm erzählten Novellen sind nur zwei, die nicht
anstössig wären, und auch von diesen beiden ist noch die eine,
obwohl frei von Liebesabenteuern, voll von anderen kräftigen
Scherzen und Spöttereien.

82. Die erste von Dioneus erzählte Posse, worin ein Mönch sich in
die Liebe einer Dirne mit dem Abte teilt, erregt bei den Damen
Erröten und Schelten. Allmählich wagen es nun auch die beiden
anderen Jünglinge, Ähnliches vorzutragen, bei den Mädchen
überwiegt bald das Gelächter den Unwillen, und nach und nach
entschlüpft auch ihnen da und dort eine derbe Historie, bis am Ende
die Scheu ganz überwunden ist und alle ihren natürlichen
Eingebungen folgen, so dass zuletzt auch von den Damen jede
wenigstens eine oder zwei derartige Anekdoten zum Besten gegeben
hat. Dioneus freilich bleibt hierin obenan, nicht nur was [pg 55] die
Anzahl, sondern auch was die Stärke seiner Possen betrifft. Welcher
Novelle in dieser schlimmen Hinsicht der Vorrang gebühre, mag
jeder für sich entscheiden. Aber auch davon abgesehen, dass alle
diese von der sinnlichen Liebe handelnden Stoffe mit vieler
Schönheit und Kunst vorgetragen werden, sind Reden und
Benehmen der zehn jungen Leute im übrigen so ehrbar und
tadelfrei, dass man wohl sehen kann, wie Reden und Tun zweierlei
Dinge sind und wie Freimütigkeit sich mit guter Sitte sehr wohl
verträgt. Darin könnte sogar mancher von den Erzählern der hundert
Novellen viel Nützliches lernen.
Im Ernst möchte ich keinem klugen Leser raten, die
unanständigeren Novellen des Dekameron völlig zu überschlagen.
Wer selbst von guter und reinlicher Natur ist, wird gewiss das
wirklich Unsäuberliche von selber liegen lassen. Davon abgesehen,
offenbart sich aber gerade in einigen der derberen Geschichten die
Art des Boccaccio am besten, so dass man in ihnen ebenso die
grosse Anschaulichkeit und Wahrheit der Darstellung [pg 56] wie die
Lebendigkeit der Sprache bewundern muss. Es sind von Alters her

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