Cold Microphysical Effects on Surface Rainfall Variability in the Tropics

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0125706GeorgakakosThe focus of the two-year research project is to quantify the relativeimportance of (a) the large-scale forcing fields of water vapor andthermal buoyancy versus (b) the storm microphysics for the developmentof the spatio-temporal characteristics of convective oceanic surfacerainfall variability. Of particular interest is to understand theeffects of cold microphysical properties on rainfall variability atvarious spatiotemporal domains and resolutions. The research studiesoceanic rainfall as a first step toward the understanding of the causesof rainfall variability by separating the large scale forcing andmicrophysics from the complex terrain influences present in continentalrainfall. The research results are of fundamental importance forhydrometeorology and hydrology, and they may be used in applicationssuch as (a) downscaling or upscaling rainfall estimates obtained byremote sensing or by large-scale climate models, or (b) hydrologicdesign studies requiring rainfall estimates of high spatio-temporalresolution. Statistical-dynamical numerical models of rainfall genesisand evolution are combined with data from national large-scaleexperiments to achieve the goals of the project. State equations forthe vertical momentum, mass and energy conservation are integratedefficiently using typical vertical profiles of the state variables,estimated from field experiments in convective regimes. A number ofquantitative hypothesis are tested regarding the causes of rainfallvariability in domains of a 256-km length, with spatial resolution of 1km and temporal resolution of 1 min. The models are used in aMonte-Carlo framework that incorporates uncertainties in observed data,large-scale forcing fields, and model microphysical parameterizations,including possible feedbacks from the generated cloud to the near fieldlarge-scale forcing.