Studying Himalayan Snow - Indian Monsoon Relationship by Some LULCC Sensitivity Experiments in REGCM4.0

This study re-examines the relationship between Himalayan snow and Indian monsoon and impact of land surface degradation due to depletion of Himalayan glaciers on Indian monsoon precipitation and circulation patterns using land-use land-cover change (LULCC) sensitivity experiments. For performing the sensitivity experiments, simulations are done using Biosphere Atmosphere Transfer land Surface (BATS) scheme coupled regional climate model (RegCM4.0) simulations is done at 0.44 o resolution using NNRP2 data as boundary forcings for evolution of meteorological variables. Results from sensitivity experiments (heavy snow and tundra) confirm that precipitation has decreased over whole Indian mainland (significant at 99% level of confidence) but increased over North India, Pakistan, Western Ghats, Arabian Sea and Bay of Bengal. From our analysis though strength of south-westerlies over Arabian Sea and easterlies over Bay of Bengal has increased but reduced mid-tropospheric north–south temperature gradient has actually weakened the Indian summer monsoon rainfall by not allowing the easterlies reach the land regions of Indian subcontinent. Results from second sensitivity experiment (representing land degradation over the Himalayan region) shows that over Indian subcontinent 2 metre- temperature, temperature upto 700 hPa increases. Runoff increases in the arid regions, whereas over Indo-Gangetic plains and east India runoff decreases.