10-An observational study of tropics mid-latitude interactions during different seasons.

Abstract

Over Indian region when the tropical easterly troughs and the extratropical westerly troughs come closer longitudinally, they interact and amplify each other, while maintaining their distinct identities. This level of interaction varies with season, and goes up in height from 350 hPa during winter to 500 hPa during monsoon. During interaction, in winter, pre- and post-monsoon seasons, the tropical easterlies extend considerably into northern latitudes in lower tropospheric levels. The extratropical westerlies extend considerably equatorward in upper tropospheric levels. In monsoon this interaction is responsible for the northward propagation of monsoon pulses from the equatorial region to the foot hills of the Himalayas. The tropics-mid-latitude interactions provide the necessary dynamics for the development and steering of the rain-giving systems in all seasons.