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Simulation of the Indian monsoon using the RegCM3-ROMS regional coupled model

Ratnam, J. Venkata, Giorgi, Filippo, Kaginalkar, Akshara, Cozzini, Stefano
Climate dynamics 2009 v.33 no.1 pp. 119-139
climate models, energy, monsoon season, rain, surface temperature, wind
A regional coupled atmosphere-ocean model was developed to study the role of air-sea interactions in the simulation of the Indian summer monsoon. The coupled model includes the regional climate model (RegCM3) as atmospheric component and the regional ocean modeling system (ROMS) as oceanic component. The two-way coupled model system exchanges sea surface temperature (SST) from the ocean to the atmospheric model and surface wind stress and energy fluxes from the atmosphere to the ocean model. The coupled model is run for four years 1997, 1998, 2002 and 2003 and the results are compared with observations and atmosphere-only model runs employing Reynolds SSTs as lower boundary condition. It is found that the coupled model captures the main features of the Indian monsoon and simulates a substantially more realistic spatial and temporal distribution of monsoon rainfall compared to the uncoupled atmosphere-only model. The intraseasonal oscillations are also better simulated in the coupled model compared to the atmosphere-only model. These improvements are due to a better representation of the feedbacks between the SST and convection and highlight the importance of air-sea coupling in the simulation of the Indian monsoon.