Cold Microphysical Effects on Surface Rainfall Variability in the Tropics

Hydrologic Research Center, San Diego CA

Investigators

Abstract

0125706 Georgakakos The focus of the two-year research project is to quantify the relative importance of (a) the large-scale forcing fields of water vapor and thermal buoyancy versus (b) the storm microphysics for the development of the spatio-temporal characteristics of convective oceanic surface rainfall variability. Of particular interest is to understand the effects of cold microphysical properties on rainfall variability at various spatiotemporal domains and resolutions. The research studies oceanic rainfall as a first step toward the understanding of the causes of rainfall variability by separating the large scale forcing and microphysics from the complex terrain influences present in continental rainfall. The research results are of fundamental importance for hydrometeorology and hydrology, and they may be used in applications such as (a) downscaling or upscaling rainfall estimates obtained by remote sensing or by large-scale climate models, or (b) hydrologic design studies requiring rainfall estimates of high spatio-temporal resolution. Statistical-dynamical numerical models of rainfall genesis and evolution are combined with data from national large-scale experiments to achieve the goals of the project. State equations for the vertical momentum, mass and energy conservation are integrated efficiently using typical vertical profiles of the state variables, estimated from field experiments in convective regimes. A number of quantitative hypothesis are tested regarding the causes of rainfall variability in domains of a 256-km length, with spatial resolution of 1 km and temporal resolution of 1 min. The models are used in a Monte-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 field large-scale forcing.