Role of Indian Ocean sea surface temperatures in modulating northwest Indian winter precipitation variability

Summary The interannual variability of North-West India Winter Precipitation (NWIWP) has been examined in association with the variability of sea surface temperature (SST), surface air temperature (SAT) and upper tropospheric (200 hPa) wind patterns over India and the surrounding regions. We have considered data for a period of 54 years (1950–2003). During the years of excess NWIWP, the SST was above normal over the equatorial Indian Ocean, SAT was below normal over east Mediterranean Sea and over the Himalayan region and upper tropospheric westerlies strengthen and shift southwards. Upper tropospheric westerlies over north and central India was found to be related with the SST anomalies over the equatorial Indian Ocean. The decrease of SAT over north India and surroundings may largely be a manifestation of cooling brought about by excessive precipitation and sweep of cold air advection in rear of the storms. The intensifying of upper troposphere westerlies embedded with a jet increases the upper level divergence over north India due to increased horizontal shear resulting in intense anticyclone at upper troposphere.