Dott. Alfonso Crisci

1. FONDAZIONE PER IL CLIMA E LA SOSTENIBILITA’
Spatial time series breakpoint and coherency analysis of
climate-vegetation relationship in eastern Africa
Crisci A.1, Grasso V. 1,Capecchi V. 1,Genesio L.1, Bacci M.1, Tarchiani V.1,Di Vecchia A.1 and Vignaroli P.2
1 National Research Council of Italy - Istitute of Biometeorology (CNR-IBIMET) ; 2 Climate and Sustainability Foundation (FCS)
Introduction Results
Food security in East Africa region essentially depends on the Focusing on Ethiopia country, where agriculture sector accounts for
47% of the GDP, provides 85% of employment and 90% of foreign
stability of rain-fed crops farming, which renders its society
currency earning, some preliminary results obtained using this
vulnerable to climatic fluctuations. These ones in Africa are methodology are shown.
most widely and directly related to rainfall. The CPSZ2 project is Legend
an initiative of Joint Research Centre of European Union to Eth_g2
Time Series Analysis
upgrade ad modernize the Crop Production System Zones Priority MUs
No changes
Database of the IGAD Region (CPSZ). The CPSZ database, Low
Medium
realized by FAO and co-funded by the Italian Cooperation is a
High
unique information system for the agricultural monitoring and
early warning activities on the seven countries of the Horn of
Africa: Djibouti, Eritrea, Ethiopia, Kenya, Sudan, Somalia and
Uganda.
In four different district ( Gambella, Oromia, Afar and SNNP) some
administrative unit have shown significant breakpoints in indicators
series as highlighted in orange and red in the map. Years presenting
breakpoints are: 2000, 2002, 2004/2005, with slight differences in
IGAD NDVI climatology IGAD Potential Evapotraspiration IGAD Length of season map function of the methodology employed. In the period 1999-2009, driving
forces of high impact events as reported by Google News
Methods ArchiveSearch queries, are evaluated to be different for each area both
The relationships between recent spatial rainfall variability and from quantitative and qualitative point of view.
vegetation dynamics has been investigated for East Africa In Gambella unit sociological factor linked to refugees displacement
territories. NDVI (Normalized Difference Vegetation Index) from have prevailed, while in other areas major drought episodes signature
( 1999/2000 and 2002/2003) or heavy floods (2006) have emerged. GE
SPOT-4 Vegetation satellite 1 km resolution and RFE (Rainfall
mash–up main elements are shown for the Oromia-Arsi units as
Estimates) from Famine Early Warning Systems Network (FEWS
demonstration in the following figures.
NET) are used. The survey is performed at administrative level
Oromia Arsi
scale using 10-day summaries extracted from raster dataset for
BFAST breakpoints analisys NDVI
each spatial area unit, thanks to specific polygonal theme. Data
time span covers two different periods: 1996-2009 for rainfall
estimates and 1999-2009 for NDVI.
BFAST breakpoint analysis ( Verbesselt et al, 2010) on 10-day
rainfall estimates and on NDVI time series for each administrative
unit has been carried out for IGAD regions. Moreover to
understand the spatial and temporal patterns of ecosystem BFAST breakpoints analisys rainfall
dynamics in response to climatic variability, NDVI–rainfall
relationships are investigated using wavelet spectral coherence
between time series (Maraun and Kurths, 2004) . Hot spot detection
methodology is obtained from time series analysis carried out on
the RFE and NDVI time series. The main drivers for hot spot
detection are: (i) the significant annual breakpoints detected and
(ii) the temporal range of coherence between NDVI and rainfall.
These ones indicates the zones where and when significant
changes in agricultural production systems might have occurred.
For each mapping unit, the significant breaks detected over the
Google News ArchiveSearch
time series of indicators could be related to the response of 1999-2009 annual frequency NDVI-rainfall time series NDVI-rainfall time series
wavelets coherency
vegetation and to the agro-climatic conditions. The score reports wavelets phase
framework built using the two techniques provides three classes of
magnitude of change: low, medium and high level; the results are References
incorporated as theme layer trough GIS procedure. To facilitate the Google ArchiveSearch 2009 http://news.google.com/archivesearch/advanced_search
Verbesselt J., Rob Hyndman R., Zeileis A., Culvenor D, Phenological change detection while accounting for abrupt and gradual trends in
dissemination and sharing of information an interactive map has satellite image time series, 2010, Remote Sensing of Environment, Volume 114, Issue 12, ISSN 0034-4257,
DOI:10.1016/j.rse.2010.08.003.
been implemented with Google Earth® (GE) mash-up. Finally a Web Maraun, D., & Kurths, J. 2004, Nonlinear Process. in Geophys., 11, 505
ArchiveNews Google service has been nested inside the GE mash-
Contacts
up to give further informative reading keys on hystorical variation
occurred in the investigated areas. www.ibimet.cnr.it
Africa projects & initiatives: Patrizio Vignaroli, p.vignaroli@ibimet.cnr.it
A demo on Ethiopia is shown in the results section Lorenzo Genesio, l.genesio@ibimet.cnr.it
Statistical Methodology: Alfonso Crisci, a.crisci@ibimet.cnr.it
Communication: Valentina Grasso, vgrasso@ibimet.cnr.it
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