The development of weather radar as a research and operational tool for hydrology in South Africa

Abstract

An overview of weather radar-related developments in South Africa, specifically aimed at hydrological research and operations, is given. Hydrometeorological applications of weather radar have their roots in the country's long-standing research effort on rainfall enhancement from summertime convective storms. This programme has developed the necessary infrastructure, expertise and related hardware and software to collect and archive high-quality radar data, analyse the information and conduct comparisons with conventional measurements on catchment scales. The high spatial and temporal resolution, and real-time nature of radar data have distinct advantages over even dense raingauge networks when catchment rainfall under convective conditions is estimated for flood hydrology. These advantages are highlighted by two case studies presented. The information gained from radar data has also provided insight into the structure of rain-producing systems, enabling the more accurate modelling of the phenomenon. Shortcomings of weather radar data for hydrological applications are described and the ongoing research efforts to address these shortcomings are highlighted. These include methods to reduce the impact of ground clutter, anomalous propagation, hail and the bright band on rainfall estimates. It also includes methods to extend the useful range of radar data for rainfall estimation, necessitated by the less-than optimal radar spacing over South Africa. Furthermore, some of the plans to optimise the use of the radar infrastructure are highlighted with specific reference to the radar networking system and how radar rainfall estimates might be integrated with satellite rainfall estimates and measurements by conventional gauges.