COLA Report 65

GCM Simulation of the relationship between spring Eurasian snow and Indian summer monsoon

A.S. Bamzai and L. Marx

March 1999


Abstract

In this study, we test the ability of the Center for Ocean-Land-Atmosphere Studies Atmospheric General Circulation model (COLA AGCM) to capture the inverse snow-monsoon relation observed in satellite-derived data. The effect of initial enhanced and reduced spring Eurasian snow mass on the evolution of subsequent Indian summer monsoon is examined through 11-member ensemble integrations from March 1 to October 1. The anomalies introduced are based on model snow mass climatology for spring; although large, they are more realistic than some of the snow mass anomalies used in past sensitivity experiments to test the snow-monsoon hypothesis.

The results of the sensitivity experiment indicate that remote responses to snow mass anomalies include significant changes in the sensible heat flux, latent heat flux and sea level pressure, leading to changes in summer precipitation over the land mass of the Indian subcontinent. For the pre-monsoon season, the ensemble average temperature of the atmospheric column for the enhanced snow mass is anomalously lower over large-scale regions of the Eurasian continent compared to the corresponding ensemble average for the reduced snow mass. Low level southwesterlies associated with the monsoonal circulation are greater for the reduced snow experiment. The results indicate the importance of land-surface processes in the evolution of monsoon circulation and lend hope to the use of Eurasian spring snow mass towards improved forecasting of the subsequent summer monsoon.

Complete copies of this report are available from:

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(301) 595-7000
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jperez@cola.iges.org

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last update: 9 February 1999
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