Integration of Radar and Raingage Data for Improved Rainfall Measurement

Abstract

Oklahoma thunderstorm data were used to determine how the estimation of area rainfall by radar can be improved by using one or several raingages. The radar data were collected between 1964 and 1968 with the WSR-57 radar at the National Severe Storms Laboratory, Norman, Okla. The rainfall data were obtained from the Agriculture Research Service's dense network of raingages near Chickasha, Okla. The improvement of area rainfall measurements by combining radar measurements with discrete raingage measurements is demonstrated. It is shown, for example, that the rms error of radar measurements of storm rainfall amount, for a 1000 mi2 area, was reduced by 39% after the radar was calibrated with only one rain-gage. At least four uniformly spaced gages are required to measure storm rainfall amounts for the same area as accurately as the radar calibrated with only one gage. The present network of gages over the United States is approximately one gage per 1000 mi2. The ability of radar to measure rainfall variability accurately has been demonstrated; therefore, it is possible to assess objectively whether a particular gage measurement will be useful for adjusting radar rainfall measurements. With the recent development of an effective system for automatically digitizing and communicating radar data in a form suitable for computer processing, these findings make possible the development of an operational system for measuring rainfall with an accuracy and timeliness never before achieved.