Rain drop size distribution variability and impact on X‐band polarimetric radar retrieval: Results from the AMMA campaign in Benin

Abstract

AbstractDuring the African Monsoon Multidisciplinary Analysis (AMMA) field campaign, polarimetric weather radars, a rain‐gauge network and disdrometers were available to analyse the convective systems and the rainfall in Benin. In this paper a three‐year dataset of drop size distributions is used to compute theoretical relationships between X‐band polarimetric variables and the rain rate, adjusted for the region of interest. The variability of these relationships from storm to storm and between rain types is studied. With an X‐band polarimetric radar the rain rate can be retrieved from the differential specific phase shift KDP, the specific attenuation AH, the reflectivity Z or differential reflectivity ZDR corrected for attenuation, or a combination of these variables. The set of coefficients needed to run the rain retrieval or the attenuation correction schemes under the conditions found in Benin are computed. The rain retrieval schemes are compared on the basis of simulations. The retrievals based on one single propagative variable like KDP or AH perform well. Preliminary results from direct comparisons between X‐band polarimetric radar estimates and rain‐gauges are consistent with the disdrometer‐based analysis. Copyright © 2010 Royal Meteorological Society