A modeling study of diurnal rainfall variations during the 21-day period of TOGA COARE |
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Authors: | Shouting Gao Xiaopeng Cui Xiaofan Li |
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Institution: | Laboratory of Cloud-Precipitation Physics and Severe Storms (LACS), Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029,Laboratory of Cloud-Precipitation Physics and Severe Storms (LACS), Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029,Joint Center for Satellite Data Assimilation and NOAA/NESDIS/Center for Satellite Applications and Research, Camp Springs, Maryland, USA |
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Abstract: | The surface rainfall processes and diurnal variations associated with tropical oceanic convection are
examined by analyzing a surface rainfall equation and thermal budget based on hourly zonal-mean data from a series
of two-dimensional cloud-resolving simulations. The model is integrated for 21 days with imposed large-scale vertical
velocity, zonal wind, and horizontal advection obtained from the Tropical Ocean Global Atmosphere Coupled
Ocean-Atmosphere Response Experiment (TOGA COARE) in the control experiment. Diurnal analysis shows that the
infrared radiative cooling after sunset, as well as the advective cooling associated with imposed large-scale
ascending motion, destabilize the atmosphere and release convective available potential energy to energize
nocturnal convective development. Substantial local atmospheric drying is associated with the nocturnal rainfall
peak in early morning, which is a result of the large condensation and deposition rates in the vapor budget.
Sensitivity experiments show that diurnal variations of radiation and large-scale forcing can produce a
nocturnal rainfall peak through infrared and advective cooling, respectively. |
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Keywords: | diurnal rainfall variation cloud-resolving simulation tropical oceanic convection TOGA COARE |
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