Statistical characteristics of rainstorms derived from weather radar images

Abstract

The hydrologic response of urban catchments is sensitive to small scale space-time rainfall variations. A stochastic rainfall model must reproduce important statistics at these scales. Using an extensive database of weather radar images for the Sydney region, a detailed study of the variation of important statistics within and between storms is undertaken. The statistics include wet area ratio, correlation length scales, and transformation parameters to render the rainfield approximately Gaussian. It was found that large variation occurred within and between storms and that uni- and bivariate AR(1) models could adequately describe within-storm variation. The results suggest that key statistics describing the stochastic evolution of rainfields at 10-minute, 1 km2resolution exhibit strong time dependence. This has significant implications for the development of stochastic rainfall models at this scale.