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Effect of Tibetan snow on Indian Summer monsoon rainfall using RegCM2.5

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Introduction The summer monsoon of southwest Asia is the largest anomaly of general circulation ... monsoon circulation features and ... – PowerPoint PPT presentation

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Title: Effect of Tibetan snow on Indian Summer monsoon rainfall using RegCM2.5


1
Effect of Tibetan snow on Indian Summer monsoon
rainfall using RegCM2.5
M. S. Shekhar S. K. Dash Indian Institute of
Technology Delhi Hauz Khas, New Delhi
-110016 India
Workshop on Theory and use of Regional Climate
Model (RegCM3)
2
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.
3
Objectives
? To simulate Indian summer monsoon circulation
features and Rainfall over the Indian region
using RegCM2.5.
? To conduct sensitivity experiments by using
snow depth over Tibet to study its effect on
Indian summer monsoon rainfall.
4
Domain Information
Central Latitude- 20oN
Central Longitude- 80oE
115 Points along the longitudinal direction
101 Points along the latitudinal direction
55oE to 105oE and 5oS to 45oN
Grid distance- 110 Km
Mercator Projection
Data used
PSU/NCAR global 30 resolution terrain and
landuse data. Monthly OI SST available from
NCEP ECMWF TOGA/WCRP uninitialized data 4 times
daily
5
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6
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7
Subdivisional Rainfall over India- 1994
8
Subdivisional Rainfall over India- 1995
9
All India Rainfall-1994 All India Rainfall-1995
Grell Snow IMD

June 8.06 7.73 17.54

July 32.66 23.91 35.67

Aug 31.67 29.97 29.14

Sep 19.94 19.88 23.16

92.33 81.49 105.51
Grell Snow IMD

June 24.64 18.18 27.46

July 30.05 24.24 40.54

Aug 22.2 16.99 29.92

Sep 12.72 10.14 15.37

89.61 69.55 113.29
10
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.
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