9502817 Vernekar The objective of this project is to investigate various aspects of the behavior of the Indian monsoon. The principal investigator will develop a regional model which is appropriate for testing hypotheses concerning mechanisms governing the onset of the monsoon, the northward propagation of the onset over the Indian subcontinent, monsoon break periods, and monsoon withdrawal. Towards this end, the principal investigator already has successfully linked the National Meteorological Center's (NMC) eta model to the global general circulation model to simulate monsoon behavior. The eta model is used primarily for short-range predictions and simulates a number of physical processes including the physics of the boundary layer, the diurnal cycle, radiation interactions with clouds, and convection. The surface physics module, currently a simple slab energy and bucket hydrology model, will be replaced with a state-of-the-art biosphere model. This biosphere model should provide more realistic representations of the hydrologic cycle as governed by soil moisture and vegetation. Once implemented, the coupled model's simulated surface fluxes will be compared with observations. The coupled model will then be used to simulate the monsoon from the beginning of May to the end of September. To assess the ability of the model to simulate the space-time variability of the monsoon, the time- averaged fields as well as the transient characteristics produced will be compared with those from observation. Finally, the various hypotheses of monsoon behavior will be tested with the coupled model. ***
