Impact of small-scale rainfall variability on larger-scale spatial organization of land-atmosphere fluxes

A coupled modeling framework is used in this study to investigate the effec t of subgrid-scale rainfall variability on the spatial structure of the evo lving storm and on other surface variables and water and energy fluxes. The Fifth-Generation Pennsylvania State University-National Center for Atmosph eric Research Mesoscale Model coupled with the Biosphere-Atmosphere Transfe r Scheme is combined with a dynamical/statistical scheme for statistically downscaling rainfall. Model simulations with and without including subgrid- scale rainfall variability are compared at the grid scale to quantify the p ropagation of small-scale rainfall heterogeneities through the nonlinear la nd-atmosphere system. It was found that including subgrid-scale rainfall va riability (here on the order of 3 km) affects the spatial organization of t he storm system itself, surface temperature, soil moisture, and sensible an d latent heat fluxes. These effects were found to occur at spatial scales m uch larger than the scale at which rainfall variability was prescribed, ill ustrating the pronounced nonlinear spatial dynamics of the land-atmosphere system and its important role on hydrometeorological predictions.