Evaluation of Rain Gauge Network Density and NEXRAD Rainfall Accuracy

The distribution of rainfall in space and time measured by a rain gauge network is a critical element in the management of precious water resources, whether the network is used alone or in combination with weather radar. In 2004, the District initiated a program to optimize the rain gauge network for purposes of near-real time and end of month adjustment of radar data. The rainfall measurement accuracy achieved by a given network density depends on the range correlation defined by radar and the point variance measured at each rain gauge in the network. The point variance and range parameter of the semivariogram vary across the analysis blocks intersecting the District. A variable number of gauges designed to achieve a constant accuracy requirement can be determined. Gauge-adjusted radar rainfall estimate variations based on rain gauge density were analyzed.