Evaluation of present-day rainfall simulations over West Africa in CORDEX regional climate models
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Abstract
The objective of this study is to evaluate the ability of seven CORDEX regional climate models (RCMs), driven by ERA-Interim reanalysis dataset to simulate the observed rainfall characteristics over West Africa during the period of 1990–2008. The seasonal climatology, annual rainfall cycles, interannual variability, 850 hPa specific humidity, and wind fields of the RCMs outputs were assessed over a number of spatial scales covering three climatically homogenous subregions (Guinea Coast, Savannah, and Sahel) and the entire West Africa domain. The ability of the RCMs to simulate the response to El Nino and La Nina events were further assessed. Results indicate that the RCMs captured the spatial pattern of rainfall and the three distinctive phases of the West African monsoon reasonably. It is worth noting that RCA and CRCM5 failed to distinctively reproduce the monsoon jump while CCLM, HIRHAM, and REMO largely overestimated the amount of the pre- and the post-monsoon rainfall. The analysis also showed significant biases in individual models depending on the subregion and season under consideration. These biases appear to be linked to the model’s failure to resolve convective processes and topography accurately. The majority of the RCMs used were consistent with the ground observation in capturing the dry (wet) conditions associated with the El Nino (La Nina) events. Statistical analysis conclusively revealed that the RCMs performance varies over the subregions and seasons, implying that no single model is best at all time. In general, REGCM3 was found to be the most outstanding of all the RCMs and is therefore recommended for use in rainfall assessment over West Africa.
Keywords
CORDEX-Africa West African monsoon Climatology Precipitation characteristicsNotes
Acknowledgements
The authors appreciate WCRP and START for setting up and funding the CORDEX-Africa analysis initiative and the University of Cape Town for leading the training and analysis program. We are very grateful to regional downscaling groups who kindly shared the downscaled data used in this analysis. We are grateful to the services that have operated the TRMM and CRU and also the African rainfall database of the Institute of Geophysics and Meteorology, University of Cologne, Germany, for the provision of the ground observation data. The efforts of Mr. Abolude Akintayo Temiloluwa and the two anonymous reviewers are also acknowledged.
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