Large-scale summer monsoon rainfall over India and its relation to 850 hPa wind shear

Abstract

The daily variations of the horizontal wind shear at the 850 hPa level between a southern region (5-15°N, 40-80°E; Zone 1) and a northern region (20-30°N, 70-90°E; Zone 2) during the period 1979-2002 were investigated. Investigations revealed that the changes of this wind shear on a daily basis are directly related to the large-scale rainfall over the Indian region during the monsoon season. The wind shear of zonal wind together with Zone 2 is useful for determining active, weak and break periods of the Indian summer monsoon (ISM). Thus, the Horizontal Wind Shear can be used as a dynamical circulation Index (HWSI) for studying ISM variability. Copyright © 2007 John Wiley & Sons, Ltd.