The Reduction of Errors Caused by Bright Bands in Quantitative Rainfall Measurements Made Using Radar

Abstract

The presence of melting snow in a radar beam produces a highly enhanced return which can lead to large errors in estimates of areal surface rainfall made with radar. This paper describes an algorithm for use in real time to detect the presence of bright bands in conventional (non-Doppler) weather rádar data. The algorithm derives values for the characteristic parameters of height and intensity of the bright band which can then be used to calculate a correction. Detection relies on the fact that the bright band causes a peak in the apparent rainfall rate measured by the radar at a range dependent on its height above the radar and the elevation of the radar beam. Analysis of about 270 hours of data collected over a period of five months shows that the algorithm is reliable. It detects the bright-band effect when it occurs and there is sufficient precipitation present and does not raise any false alarms. When the precipitation is patchy it is able to identify the bright band correctly but not with enough confidence to apply a correction. When a correction is applied the ?error? is reduced by approximately 50% on average.