Comparison of space and ground-based radar reflectivity and derived rainfall

Data from the African Monsoon Multidisciplinary Analyses (AMMA) and NASA-AMMA (NAMMA) 2006 field campaigns were used for a comparative analysis with TRMM precipitation radar (PR) products. Approximately 20 cases were analyzed of varying spatial extent of the meteorological echo. Six mesoscale convective systems, many of which were associated with African easterly waves, are included in our study. Previous studies suggest that rainfall from MCS storms contribute nearly 90% of the seasonal precipitation in the Sahelian region.

Examination of AMMA/NAMMA radar data from three sites: Niamey, Niger; Kawsara, Senegal; and Praia, Cape Verde Islands was emphasized, given quantitative radar data were obtained at these locations. The ground-based scan domains corresponded to continental, coastal and maritime locations, respectively. The Niamey (MIT) and Praia (TOGA) are C-band Doppler radars, while the Praia (NPOL) is an S-band dual polarization Doppler radar. TRMM PR orbital tracks within 120 km proximity to each radar location were matched with ground-based full volume scans.

Horizontal reflectivity maps and vertical reflectivity profiles were analyzed for relative agreement and distribution of reflectivity as a function of regional location. Additionally, the latitudinal location of all radars was near 15°N, a transitional region in terms of the northward propagation of the Gulf of Guinea moist air mass that is transported during the monsoon season. This transition region allows for a variety of spatial extent and regime types of observed systems. Reflectivity data from each radar were used to derive rainfall estimates. Comparison of the rainfall estimations allows insight into instrument agreement and quality of the rainfall estimated products via TRMM.