Submitted to: Precipitation Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 6/25/1998
Publication Date: N/A
Technical Abstract: Large spatial gradients in precipitation intensity may be observed at any instant in severe thunderstorms and heavy rainfall events. On longer time scales, however, we anticipate that such gradients will be smoothed out and spatially more homogeneous rainfall distributions will result. Nonetheless, it is not uncommon to observe significant rainfall accumulation differences over short distances. We document spatial gradients in rainfall accumulations over various space and time scales using data collected within (rain gauge) and above (radar) the Goodwin Creek research watershed located in northern Mississippi. The catchment is under radar coverage from several NEXRAD WSR-88Ds, the closest being the Memphis (Tennessee) WSR-88D, at a distance of approximately 120 kilometers. Rainfall accumulation differences in excess of several tens of millimeters are observed in daily rain gauge totals over distances as little as one kilometer. We use radar data to show that such extreme spatial rainfall gradients are the result of multiple storms tracking over the same location or produced by stationary systems. Selected examples from different geographic locations illustrate that the spatial rainfall gradients observed at Goodwin Creek are by no means unique to that particular setting. This knowledge is crucial to the understanding of subgrid scale effects on the radar rainfall measurement.