Impact of Small-Scale Rainfall Variability on Larger-Scale Spatial Organization of Land–Atmosphere Fluxes

Abstract

A coupled modeling framework is used in this study to investigate the effect of subgrid-scale rainfall variability on the spatial structure of the evolving storm and on other surface variables and water and energy fluxes. The Fifth-Generation Pennsylvania State University?National Center for Atmospheric Research Mesoscale Model coupled with the Biosphere?Atmosphere Transfer 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 propagation of small-scale rainfall heterogeneities through the nonlinear land?atmosphere system. It was found that including subgrid-scale rainfall variability (here on the order of 3 km) affects the spatial organization of the storm system itself, surface temperature, soil moisture, and sensible and latent heat fluxes. These effects were found to occur at spatial scales much larger than the scale at which rainfall variability was prescribed, illustrating the pronounced nonlinear spatial dynamics of the land?atmosphere system and its important role on hydrometeorological predictions.