Climatologically tuned reflectivity-rain rate relations and links to area-time integrals

Abstract

Relations between either the point- or beam-averaged effective reflectivity, Ze, and surface rain rate, R, are determined by a probability matching method. The cumulative density functions (CDF) of reflectivity and rain rate are matched at pairs of Ri, Zi which give the same percentile contribution. One obtains range dependent Ze-R relations by stratifying the Ze data by range. Truncation of the Ze distribution by too large a threshold causes the threshold rain rate retrieved from the radar data to exceed that in the matching gage distribution. Forcing a match between the mean rate measured by the gages and those retrieved by use of a set of trial Ze-R equations provides for the adjustment of the final Ze-R relation and compensates for the truncation. The radar retrieved CDFs of rain rate then replicate the CDF of gage measured rates nicely. -from Authors