Clim. Dyn., 39, 239-258.

Very high resolution rainfall patterns measured by TRMM precipitation radar: Seasonal and diurnal cycles

Michela Biasutti
Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY.

Sandra E. Yuter and Casey D. Burleyson
Department of Marine, Earth and Atmospheric Sciences, North Carolina State University, Raleigh, NC.

Adam H. Sobel
Department of Applied Physics and Applied Mathematics, Department of Earth and Environmental Sciences, and Lamont-Doherty Earth Observatory, Columbia University, New York, NY.

Abstract

The TRMM Precipitation Radar is used to construct a high resolution (0.05x0.05) climatology of rainfall over the latitude band extending to about 37 North and South. This study describes climatological patterns of rainfall frequency and intensity at high spatial resolution, with special focus on the seasonal and diurnal cycles in the frequency of rainfall events. We use this Tropics-wide dataset to highlight small-scale precipitation features that are too fine to be captured by the most widely used satellite-based rainfall datasets. The results shed light on the roles of changes in the wind direction, the land-sea thermal contrast, small-scale variations in sea surface temperature, and orography in shaping the seasonal and diurnal cycles of rainfall. In some regions of the tropics, diurnally locked local circulations are largely responsible for sharp gradients in the spatial distribution of seasonal mean precipitation. In other regions, we show that climatological rainfall frequency changes very sharply at coastlines, even though rainfall in these regions is expected to be controlled by relatively large scale weather systems.