Wednesday, 16 January 2002: 5:15 PM
Spatial and Temporal Organization of Convective Activity in the Himalayan region during the Asian Monsoon
The spatial and temporal evolution of mesoscale convective weather systems and short-lived convection in Northern India, along the Himalayan range and in the Tibetan Plateau were analyzed during the 1999, 2000 and 2001 monsoon seasons using METEOSAT-5 IR imagery. Rainfall and lightning data were also used in the interpretation of the results. An interesting finding of this study was the delineation of space-time patterns in the life-cycle of convective systems which suggest landform and orographic controls in establishing a convergence zone in the valley of the Ganges between the Great Indian Desert to the West and the Khasi Hills to the East, which we call the Northern India Convergence Zone (NICZ). The NICZ exhibits strong nighttime activity with the development of disorganized short-lived convection (1-3 hours) along the front range of the Middle Himalaya at elevation between 2000 and 4000m. These systems are concurrent with nocturnal peaks of intense rainfall in the region between midnight and 3 AM. Consistent with solar forcing, convective cloud clusters predominate in the low level plains of the Uttar Pradesh and in the Tibetan Plateau during the afternoon and early evening. Finally, the intra-annual and inter-annual variability of convective activity in the NICZ was assessed with respect to large-scale synoptic conditions, monsoon activity in the Bay of Bengal, and the modulating role of orography.