Recent changes in the circulation parameters and their association with Indian summer monsoon rainfall

The phenomena of Earth's climate system and its associated rainfall are mainly driven by the changes in various circulation parameters embedded with the local atmospheric instability. An attempt has been made in the present study to examine the recent changes in four selected regional circulation parameters viz., zonal wind at 200 hPa level over Tibetan Anticyclone region (TAU200), zonal wind at 100 hPa over peninsular India i.e. Tropical Easterly Jet (TEJU100), meridional wind (Somali Jet) at 850 hPa over Somali Coast (SJV850) and meridional wind at 850 hPa over Arabian Sea (ASV850) using NCEP/NCAR reanalysis dataset during the period 1949–2008. The influences of these circulation parameters in the Indian summer monsoon rainfall (ISMR) have also been brought out. ASV850 and TEJU100 show decreasing tendency which in turn leads to the weakening of the moisture transport mechanism over the Indian sub-continent during the monsoon season whereas the other parameters TAU200 and SJV850 show increasing tendency. TEJU100 shows highly significant decreasing trends throughout the monsoon months and season with a very strong positive relationship with ISMR. The intensity of the TAU200 on monthly scale seems to have less impact as compared to the other circulation parameters on ISMR during the warming scenario though it plays a vital role in modulating the general atmospheric circulation.

► Influences of 4 circulation parameters in ISMR have been examined.
► Significant recent changes have been noticed for TEJ and Somali Jet.
► ISMR seems to be largely modulated by the large-scale atmospheric circulation.