Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 8 3 2008 10.5194/acpd-8-8773-2008 http://www.atmos-chem-phys-discuss.net/8/8773/2008/ http://www.atmos-chem-phys-discuss.net/8/8773/2008/acpd-8-8773-2008.html http://www.atmos-chem-phys-discuss.net/8/8773/2008/acpd-8-8773-2008.pdf 8773 8816 2008-05-16 Effect of explicit urban land surface representation on the simulation of the 26 July 2005 heavy rain event over Mumbai, India M. Lei D. Niyogi climate@purdue.edu C. Kishtawal R. A. Pielke A. Beltrán-Przekurat T. E. Nobis S. S. Vaidya Purdue University, Department of Earth and Atmospheric Sciences and Department of Agronomy, West Lafayette, IN 47906, USA SAC/ISRO, Ahmedabad 380015, India University of Colorado at Boulder, CIRES, Boulder, CO 80309, USA Indian Institute of Tropical Meteorology, Homi Bhabha Road, Pune 411008, India We investigate whether explicit representation of the urban land surface improves the simulation of the record-breaking 24-h heavy rain event that occurred over Mumbai, India on 26 July 2005 as the event has been poorly simulated by operational weather forecasting models. We coupled and conducted experiments using the Regional Atmosphere modeling system (RAMS 4.3), with and without an explicit urban energy balance model-town energy budget (TEB) to study the role of urban land – atmosphere interactions in modulating the heavy rain event over the Indian monsoon region. The impact of including an explicit urban energy balance on surface thermodynamic, boundary layer, and circulation changes are analyzed. The results indicate that even for this synoptically active rainfall event, the vertical wind and precipitation are significantly influenced by urbanization, and the effect is more significant during the storm initiation. Interestingly, precipitation in the upwind region of Mumbai city is increased in the simulation, possibly as a feedback from the sea breeze – urban landscape convergence. We find that even with the active monsoon, the representation of urbanization contributes to local heavy precipitation and mesoscale precipitation distribution over the Indian monsoon region. 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