92nd American Meteorological Society Annual Meeting (January 22-26, 2012)

Thursday, 26 January 2012: 2:15 PM
Global Light Rainfall Retrieval and Its Importance in Quantification of Sea Surface Water Exchange
Room 256 (New Orleans Convention Center )
Ali Behrangi, JPL/California Institute of Technology, Pasadena, CA; and S. wong, B. H. Lambrigtsen, and E. J. Fetzer

Our recent study using TRMM Multisatellite Precipitation Analysis (TMPA; 3B42-V6) and estimates of surface evaporation fluxes (E) from the Goddard Satellite-based Surface Turbulent Fluxes (GSSTF) suggests that the quasi-globally and climatologically averaged surface water exchange (P-E) over the ocean is not zero and is much more negative than what is obtained from the reanalysis data product. The inconsistency in P-E between the observed and reanalysis data mainly occurs over the subtropical ocean where light rainfall is abundant. While many factors can contribute to this, poor detection and quantification of light rainfall from the majority of sensors used in global precipitation estimation is an important factor that needs to be carefully analyzed. Using coincident observation of precipitation data from Cloudsat, AMSR-E, and AMSU, and also by analyzing TRMM precipitation data, we assess how well these sensors are capturing light rainfall. We also quantify the frequency and amount of light rainfall that is likely missed from different cloud types. Our analysis of light rainfall fraction and volume not only demonstrates the importance of capturing light rainfalls to close the global surface water exchange, but also provides means to evaluate how well climate models can capture light rain events. We believe the launch and operation of GPM is an important step towards improved detection and quantification of light rainfall. This is essential in assessing the changes in water and energy cycles in a warming climate.

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