REAL-TIME CORRECTION OF WEATHER RADAR DATA FOR THE EFFECTS OF BRIGHT BAND, RANGE AND OROGRAPHIC GROWTH IN WIDESPREAD PRECIPITATION

A new method of correcting data from the United Kingdom operational weather radar network is described. The physically based scheme is designed to produce estimates of instantaneous precipitation rate at the surface by compensating for the effects of the bright band, range and low-level orographic growth. In a preliminary study, the characteristic shape of the vertical profile of reflectivity factor was examined using a climatological dataset derived from range-height indication scans recorded by a high-resolution radar. The results were then used to construct an idealized reflectivity factor profile. In the correction procedure, the heights of significant turning points in the profile are diagnosed from relevant meteorological data at each radar pixel. The parametrized profile is weighted by the radar-beam power profile and the surface precipitation rate found by an iterative method in real-time. The scheme has some important advantages over the alternative correction strategies. Detailed quantitative evaluation in typical cases of mainly frontal rainfall over southern England suggested that root-mean-square errors in estimates of instantaneous precipitation rates over 5 km pixels were reduced to less than half compared to the same radar data subject to only a fixed range correction.