Evaluation of Global Rainfall Products for Hydrological Modelling and Water Resources Management in Nigeria, Part I: Zonal and Temporal Analyses

Abstract

In a bid to provide alternative to ground observations (station data) and solve the problem of inadequate rainfall data for various climatic researches in Nigeria, six widely available reanalysis and simulated rainfall products were extensively evaluated for the period 1980–1999 (20 years), using observed rainfall data for 18 stations over Nigeria. The products evaluated were Climate Research Unit (CRU), Global Precipitation and Climatology Project (GPCP), Regional Climatic Model Version3 (RegCM3), Community Atmospheric Model Version3 (CAM3), CPC-Merged Analysis of Precipitation (CMAP) and University of Delaware Precipitation (UNIDEL). The country was grouped into Forest, Savanna and Sahel ecological zones on which the evaluation of the products was based. Annual Mean, Coefficient of Variation and time series Plots used to determine the degree of agreement between the rainfall products and station  observations (raingauge data). It was found that the performance of the products was generally better in the Sahel and in the dry  seasons than other two zones and the wet seasons, respectively. Generally, the results show that UNIDEL is the most reliable of the six products while CAM3 is the least. Although variability was high for all the products, the results could serve as basis for calibrating the products over Africa and with caution, the products could still be useful in various areas of water resources planning and development which include flood modelling, erosion control, irrigation scheduling, drainage engineering, etc.

Keywords: Evaluation, Rainfall products, Forest, Sahel, Savanna