LOW LEVEL JETSTREAM OF ASIAN SUMMER MONSOON AND ITS VARIABILITY

Asian summer monsoon rainfall affecting Indian Subcontinent and other Asian regions is the product of the global and local anomaly in the general circulation features. Awareness of the need to understand and predict the monsoon over India have recently generated much interest in the possible relationships between the amount and distribution of Indian monsoon rainfall and antecedent regional and global features. A strong cross-equatorial Low Level Jet-stream (LLJ) with core around 850 hPa exists over the Indian Ocean and south Asia during the boreal summer monsoon season, June to September. LLJ has strong horizontal shear in the planetary boundary layer and is important for the development of rain producing weather systems. The LLJ is the main conduit for transporting moisture generated over Indian Ocean to the monsoon area. The intraseasonal oscillation of LLJ controls this moisture distribution. Here it is described about the intraseasonal variability of LLJ and its relation with convective heating of the atmosphere and the role of horizontal wind shear of LLJ in the episodes of intense rainfall events observed over the west coast of India and monsoon depression genesis.