Understanding the Indian monsoon behavior in a changing climate using the IITM Earth System Model: Implications for monsoon predictability

R. Krishnan
Indian Institute of Tropical Meteorology

  15 May, Noon, in 2155

Observations indicate that the Indian landmass experienced significant surface warming at a rate exceeding 0.6oC (100 years)-1, since beginning of the 20th century. Precipitation datasets reveal a decreasing trend in summer monsoon rains over the region by about 7% since 1950s, together with significant increases in the frequency and intensity of heavy precipitation (intensity > 100 mm day-1) occurrences that have adversely affected the regional hydro-climate. We conducted numerical simulation experiments using the IITM Earth System Model (IITM ESM), which has been developed from the NCEP CFS-v2 climate forecast system, to understand the impact of climate change on the Indian summer monsoon. The IITM ESM is a radiatively balanced climate modeling framework that has been developed at the Centre for Climate Change Research (CCCR), Indian Institute of Tropical Meteorology (IITM), Pune for studying long-term climate variability and change, as well as the Earth System response to human-induced climate change.

The results from the present study point to the role of human-induced climate change on the declining trend of summer monsoon precipitation over the Indian subcontinent. In particular, the IITM-ESM simulations suggest that the combined influence of anthropogenic aerosol forcing and global warming has likely suppressed organized summer monsoon convection, weakened the monsoon circulation and in turn caused decrease of precipitation over the region. The detailed physical mechanisms of the Indian monsoon response to Greenhouse Gas (GHG) and anthropogenic aerosol forcing would be discussed during the presentation. The present findings have implications for the role of climate change on the subseasonal-to-seasonal predictability of the Indian summer monsoon.