5.2
Characterizing the space-time variability of precipitation in the Himalayan range: analysis and synthesis
Ana P. Barros, Harvard University, Cambridge, MA; and T. Lang, S. Chiao, J. Putkonen, G. Kim, and E. Williams
Through diagnostic studies combining ground-based hydrometeorological observations, radiosonde profiles, METEOSAT and TRMM satellite data, as well as simulations using a Cloud Resolving Model, we were able to identify and characterize the dominant weather systems and associated precipitation processes in the Central Himalayas: a) monsoon depressions; b) wintertime storms; c) stationary orographic gravity waves; and d) ridge-locked convection. Our analysis shows that while the first two result from large-scale conditions, and exhibit strong inter-annual variability in frequency, intensity and spatial track; the second two modulate the diurnal cycle during the monsoon. This research leads us to a synthesis of Himalayan hydrometeorology that relies on three principal modes of space-time variability: 1) an inter-seasonal mode linked to large-scale dynamics that explains infrequent events producing significant amounts of precipitation over one-three day periods (wintertime storms and monsoon depressions); 2) a regional mode linked to ocean-land-atmosphere interactions over Northern-India and the Bay of Bengal at time-scales of days to weeks consistent with the succession of rainy and dry episodes during the break and active phases of the monsoon; and 3) an orographic mode that explains the spatial variability of the diurnal cycle on the Himalayan range during the monsoon. We take further our analysis by relating our findings to climate variability and change, and propose a conceptual framework to understand past climate regimes in the Himalayas that combine our findings with lessons learned from monsoon modeling experiments using Global Climate Models. .
Session 5, Orographic hydrometeorology and the associated challenges in both observation and forecasting (Room 6E)
Thursday, 15 January 2004, 9:00 AM-12:00 PM, Room 6E
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