Numerical simulation of African rainfall : Continental and regional outlook based on ERA-Interim reanalysis

Abstract

Numerical simulation of African rainfall Continental and regional outlook based on ERA-Interim reanalysis The estimation of rainfall at continental scale over Africa is an ongoing issue due to its importance for rainfed agro-pastoral activities and also because of the lack of reliable in-situ observations. In that context numerical simulations and remote-sensing can provide useful estimates to constitute spatialized series of this parameter. In the present study the European Center for Medium Range Weather Forecasts reanalysis (ECMWF/ERA-Interim) are used to reproduce the average characteristics of rainfall over the African continent for the period 2001-2010. An assessment is conducted with RFEv2 estimates from NOAA as reference data. The performances of this satellite product are discussed here within from the results of validation studies over several regions in Africa. The results show that the reanalysis are able to simulate the rainfall seasonnal cycle over specific areas of the continent. However, biases are identified where local conditions play a major role in triggering convection (orography) or over areas where the reanalysis fail to correctly simulate the large-scale circulation (Sahel, Congo basin). It also appears that the reanalysis display too frequent rainy days and too few intense rainfall situations. Nevertheless, despite the biases regarding annual rainfall, it turns out that this data shows some skill in accounting for positive or negative seasonal rainfall anomalies over several regions.