Impact of Northwest Pacific anticyclone on the Indian summer monsoon region

Influence of northwest (NW) Pacific anticyclone on the Indian summer monsoon (ISM), particularly over the head Bay of Bengal and monsoon trough region, is investigated. Strong NW Pacific anticyclone during summer induces negative precipitation anomalies over the head Bay of Bengal and Gangetic Plain region. Westward extension of moisture divergence and dry moisture transport from NW Pacific associated with anticyclone (ridge) and local Hadley cell-induced subsidence are responsible for these negative precipitation anomalies. The impact is maximum when the anticyclone and Indian Ocean basin warming co-occur. This contributes significantly to year-to-year variability of ISM.