Modeling Rain Rate Distribution Per Diameter Class from Disdrometer Data Collected in Northern Benin (AMMA Campaign): A New Relationship Between Radar Reflectivity and Rainfall Rate.

Abstract

We analyzed the DSD with a new function R(D) which is equal to the rain rate per interval of raindrop diameters. The expressions of some weather variables (radar reflectivity Z, liquid water content W and rainfall rate RT ) were written with the function. The disdrometer data collected in northern of Benin during the African Monsoon Multidisciplinary Analysis (AMMA), were divided into two samples: DATA A and DATA B written in rain rate distribution per diameter class form (R-DSD). The R-DSD of DATA A classified by intervals of rainfall rates are averaged. Gamma function with three parameters (R T , Dc and μ) models these averaged R-DSD. Various relations are established between the parameters of these averaged R-DSD. Thus, when the moments of these R-DSD are parameterized only by the rain rate RT , we make a relationship between the radar reflectivity Z and rain rate RT . Using the sample DATA B allows us to estimate Z by this relation, on one hand, and by the classical Z-R T relation. The comparison of the two estimations allows us to state that the new Z-RT relation is in the same order as the classical Z-R T relation.