Theme 7-7-Effect of anthropogenic radiative forcings in the simulation of long-term trend and variability in monsoon climate.

Abstract

Indian Summer Monsoon plays an important role in many of socio-economic activities in the Indian Subcontinent. Water resources are most susceptible to changes in monsoon climate. An accurate and reliable portrayal of change in monsoon climate due to climate change is therefore very important in the perspective of impact of climate change on water resources. The ability of current generation of global climate models, in their long term simulations, to replicate the observed atmospheric behavior on a wide range of spatial and time scales provides support in applying these models to the regional climate change projections induced by anthropogenic radiative forcings. The ability of a coupled atmosphere ocean climate model (ECHAM3 + LSG) at T21 resolution to simulate the trends and interannual variability in area-averaged annual mean surface air temperature and summer monsoon precipitation over Indian subcontinent in three different numerical experiments viz.; control, GHG and GHG plus aerosol is examined. The model has superior skill in reproducing the observed trend and interannual variability in area-averaged annual mean surface air temperature and interannual variability (in terms of standard deviation) of summer monsoon rainfall over Indian subcontinent during the past century in GHG plus aerosol experiment. The model’s inability to simulate the observed trend in monsoon rainfall over the area of interest realistically, in all the three experiments, is a reflection of the sensitivity of simulated rainfall to meso-scale forcings such as monsoon trough, effect of complex orography not resolved at a resolution and deficiencies of parameterization scheme for convection and land surface processes.