Evaluation of satellite rainfall estimates in the Pra Basin of Ghana.

Abstract

Availability of gauged rainfall data in most developing countries at good resolution is usually a challenge since meteorological stations are usually located near urban areas. In cases where data is available some stations may still have a lot of missing values. However, in recent times, satellite derived rainfall estimates provide an alternate source of rainfall data in areas where conventional rainfall measurements are not readily available. This study evaluated the accuracy of three satellite rainfall products, TMPA 3B42RT, TMPA 3B42 and CMORPH, in the Pra basin of Ghana. Using the point-to-pixel method, data extracted from 0.25°× 0.25° satellite grids were compared with gauged rainfall measurements and analyzed using correlation coefficient (r), bias and percent bias (%Bias) as the performance evaluation methods. Seven (7) gauge stations with no missing data for the period 2003–2008 were used in the evaluation. The results, following the analysis of the data at daily, monthly, annual and seasonal timescales, showed that TMPA products performed better on all timescales considered. CMORPH on the other hand showed overestimation at all gauge locations. The TMPA 3B42 was seen to be the best amongst the three products. The overall rainfall in the basin was well depicted by the TMPA 3B42 and 3B42RT. Although there was not a perfect match between the 3B42RT and 3B42 products and the gauged rainfall, these products can be used to supplement gauged rainfall measurements in the basin and in estimation of rainfall in ungauged basins with similar characteristics.