Microphysical and precipitation characteristics of West African convection observed by polarimetric radar

Convection occurring during the West African monsoon is responsible for a significant amount of annual precipitation in the Soudanian zone (9º-12ºN) of Africa. Although the thermodynamics and organization of wet season West African convection has been the subject of many recent studies, the microphysics and subsequent precipitation processes are still not well understood. This study examines the microphysics of these convective storms using two polarimetric radars from France, the X-band XPort and C-band Ronsard radars. The radars were positioned in Benin during the Special Observing Period (SOP) of the African Monsoon Multidisciplinary Analysis (AMMA) project from June to October 2006. During this time, several squall lines, MCS and ordinary convective storms were observed. Polarimetric radar observations of several storms are presented. Differences between convection occurring before the onset of the monsoon, during the peak of the monsoon, and late in the monsoon period are also investigated.

Bulk hydrometeor types are inferred using polarimetric-based hydrometeor classification algorithms. The vertical extent and variability of hydrometeors occurring within different modes of convection are explored. Polarimetric radar observations are also used to estimate rainfall associated with different types of West African convection. Rainfall estimates are compared with ground-based disdrometer observations and available TRMM PR rain retrievals. The convective fraction, rain rate frequency, and rain volume fraction of the different cases are examined.