IUKWC Workshop November 2016: Developing Hydro-climatic Services for Water Security Session 4.5 Subimal Ghosh

1. Land Atmosphere Interactions during
Summer Monsoon
Subimal Ghosh
Department of Civil Engineering
IDP in Climate Studies
IIT Bombay
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2. Key Challenges in Hydro-meteorological
Simulations
Uncertainty across models
Bias in the models
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3. Climate Change Projections of Indian Monsoon and
Uncertainty: More Confusion, Less Consensus
 Ashfaq et al. (2009):
 Suppression
 Lee and wang (2014):
 Increase
 Chaturvedi et al. (2012):
 Increase
 Krishna Kumar et al. (2011):
 Increase
 Salvi et al. (2013):
 Non-uniform Changes with slight
increase for few scenarios
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4. Uncertainty: Not only in Future Projections but also
in present day Reanalysis4

5. But with an Improved Understanding this can
be Reduced
Sebastian et al. (2016), Scientific
Reports (Nature Publishing Group)
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6. Problems lie in the regional/ local scale simulations of
Rainfall, Evaporation
Needs improved understanding about regional processes
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7. And the Same is true at Seasonal Scale: Dry
Bias in Operational Model CFS V2
mm/day
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8. Easy Solution  Bias Correction: is it correct
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Atmospheric
Model
Bias
Correction
Hydrologic
Model
Bias corrections of the model output - a process I
liken to transforming elephants into mice. - Upmanu
Lall (AGU meet 2010)
We have bias correction methods for any sorts of bias 
We need physics based understanding of bias and physics guided model to correct them
 Can we explain a fraction of bias with understanding of land surface feedback?

9. Land Surface Feedback
Monsoon: Traditionally believed to
be governed by large scale
moisture transport from ocean
• What are their contributions?
• Can we quantify them?
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10. 12/7/2016 10
Schematic representation Precipitation Recycling
(Source: Dominguez, et al. 2006).
Evapotranspiration
Precipitable water
Time step
Local Recycling Ratio
(R or ρ)
Regional Recycling
Ratio
Recycled and Total
Precipitation
3
2
1
[(Change in atmospheric moisture storage) + (zonal moisture fraction) + (meridional
moisture fraction) ]= [ (evaporation)- (precipitation) ]
Conservation of atm. Water
vapor mass
Dynamic Recycling Model
The contribution of the
locally evaporated
water to the
precipitation in the same
region is known as
‘Precipitation Recycling’.
‘Precipitation Recycling’
is characterized by
Recycling Ratio.
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11. Recycling Ratio
Recycled
Precipitation
Recycling Ratio
Total Precipitation
Pathak et
al., (2015),
JHM
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12. Understanding Different Land and Oceanic
Sources

13. Contributions from Different Sources
Pathak et al. (2016), Jl of Climate

14. Good and Bad Monsoon Years

15. Intra-Seasonal Variations
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16. Contributions
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Pathak et al. (2016), Under Prep.

17. Impacts of Changes in LULC
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18. LULC Changes in India
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19. Impacts of LULC: Simulated Changes (WRF-CLM)
Partially Consistent with Observed Changes19
Paul et al. (2016)
Scientific Reports,
Nature Publishing Group

20. Acknowledgement
 Ministry of Earth Science (Hydrology) for funding the work
 Students
 Amey Pathak
 Supantha Paul
 Sahana A S
 Anjana Devanand
 Collaborators
 Roxy Mathew Koll (IITM)
 A K Sahai (IITM)
 Surya Chandra Rao (IITM)
 Praveen Kumar (UIUC)
 Raghu Murtugudde (UMD)
 Robert Oglesby (UNL)
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Thank You