How dependent is climate change projection of Indian summer monsoon rainfall and extreme events on model resolution?
by K. Rajendran, S. Sajani, C. B. Jayasankar and A. Kitoh
Advances in climate modelling now provide the opportunity for utilizing global general circulation models (GCMs) at very high-resolution for projections of future climate and extreme events. Diagnostics of global atmospheric GCM simulations at different horizontal resolutions of 20, 60, 120 and 180 km reveals the marked skill of 20 km mesh GCM (MRI-AGCM3.2S) in capturing regional characteristics of climatological summer monsoon rainfall over India and its frequency distribution, and mean annual variation of rainfall over most of the homogeneous regions of India. Future projections by time-slice simulations of MRI-AGCM3.2S under global warming scenario show widespread but spatially varying increase in rainfall over interior regions of peninsular, west central, central northeast and North East India (~ 5-20% of seasonal mean) and significant reduction in orographic rainfall over the west coast (~ 10-15%, consistent with the recent observed trends). MRI-AGCM3.2S projects spatially heterogeneous increase in warm days and extreme hot events (highest decile) over India.