On the impact of spatial variations of orographic frontal rainfall upon the probability matching method of radar rainfall adjustment

Assessments of the probability matching method (PMM) of adjusting radar mea surements of rainfall have largely been carried out for convective rainfall . Data from a two degree beamwidth C-band radar located close to the West P ennine moors in North West England have been used to extend these analyses to situations of orographic frontal rainfall. In this paper comparisons are made between river catchments in an area prone to low level orographic rai nfall and in an area where such effects are weak. Observed differences in t he probability density function of the rainfall are analysed. The impact of differences in the drop size distribution upon the adjustment technique ar e discussed. Finally ways in which the spatial variations may be accounted for in an operational adjustment procedure are noted. (C) 2000 Elsevier Sci ence Ltd. All rights reserved.