Interannual variability of precipitation in May over the South Asian monsoonal region.

ABSTRACT This paper investigates the interannual variability of precipitation over the South Asian monsoonal region in May, during which the South Asian summer monsoon is generally established. The South Asian monsoonal region in this study is referred to as a broad area that includes the Arabian Sea, the Indian peninsula, the Bay of Bengal, and the Indochina peninsula. The precipitation exhibits a significant enhancement in May, compared to that in the previous month. The present results indicate that the interannual variability of May precipitation in this region is significantly regulated by two independent factors: The Europe-West Asia ( EWA) teleconnection and El Niño Southern Oscillation. The EWA teleconnection pattern is characterized by the see-saw pattern of upper-tropospheric geopotential height anomalies between the Europe and the Iranian plateau. Both the factors modulate the meridional gradient of tropospheric temperature and lower-tropospheric zonal winds, and thus affect the rainfall in the monsoonal region. Therefore, both the extratropical circulation teleconnection and tropical forcing are crucial for inducing rainfall variability in May over the monsoonal region. [ABSTRACT FROM AUTHOR]