Poleward Shift in Monsoon Low Level Jetstream under Global Warming

Poleward shifts in the sub-tropical Jetstreams and mid-latitude storm tracks as well as Hadley Cell expansion have been identified as major effects of the global warming on the large scale atmospheric circulation systems. Anthropogenic weakening trends in the mean Indian Summer Monsoon (ISM) circulation and precipitation have been reported. We find that a poleward shift in the mean position of ISM southwesterly Low Level Jetstream (LLJ) has occurred in the recent decades and that shift will continue under projected global warming scenarios as assessed from the CGCM simulations. The projected shift in the mean position of the LLJ depends on the degree of warming, with the extreme warming scenario (RCP8.5) shows a shift of 1.6° northward by the end of the 21st century. These results assume significance as the LLJ plays a major role in bringing moisture from the Indian Ocean to the South Asian landmass.