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)

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.

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.

Domain Information

Central Latitude- 20oN Central Longitude- 80

oE

57 X 51 Points

50oE to 105

oE 5

oS to 45

oN

Grid distance- 110 Km

Data used

10’ USGS elevation data.

GLCC Landuse data.

OI SST

NCEP Reanalysis data-II

June 1994 July 1994

KUO

Rainfall (mm/day)

June 1994 July 1994GRELL

No snow 0.5 m. snow

June 1994

No snow 0.5 m. snow

July 1994

ConclusionsThe 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.