Effect of Tibetan snow on Indian Summer monsoon rainfall using RegCM3

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Effect of Tibetan snow on Indian Summer monsoon
rainfall using RegCM3
M. S. Shekhar (India) B. R. S. B. Basnayake (Sri
Lanka) A. U. Ahmed (Bangladesh) Group-16
Workshop on Theory and use of Regional Climate
Model (RegCM3)
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Introduction
? The summer monsoon of southwest Asia is the
largest anomaly of general circulation
? Interannual variations of summer monsoon
rainfall affects agriculture, water resources
and the economy of the country.
? The slowly varying boundary conditions at the
surface of earth provides required memory in the
climate system to predict averaged monsoon
circulation and rainfall.
? There exist an inverse relationship between
Indian summer monsoon rainfall and the extent of
Eurasian snow cover in the preceding season.
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Objectives
? To simulate Indian summer monsoon circulation
features and Rainfall over the Indian region
using NCEP/NCAR reanalysed data in RegCM3.
? To conduct sensitivity experiments by using
snow depth over Tibet to study its effect on
Indian summer monsoon rainfall.
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Central Latitude- 20oN
Central Longitude- 80oE
57 X 51 Points
Domain Information
50oE to 105oE
5oS to 45oN
Grid distance- 110 Km
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Data used
10 USGS elevation data. GLCC Landuse data. OI
SST NCEP Reanalysis data-II
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Rainfall (mm/day)
June 1994
July 1994
KUO
June 1994
July 1994
GRELL
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0.5 m. snow
No snow
June 1994
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0.5 m. snow
No snow
July 1994
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Conclusions
The Regional Climate Model (RegCM3) is able to
simulate the monsoon circulation over India
reasonably well.
The rainfall simulated in mm/day in Grell
convection scheme is closer to the observed
rainfall of the India Meteorological Department
compared to the Kuo.
The inverse snow-ISMR relationship is confirmed
by using snow depth as the boundary condition in
RegCM3.
The All India rainfall is reduced by almost
20-25 in the high Tibetan snow experiment than
in the control experiment.