Journal Article

Assessment of ERA5 and ERA-Interim in Reproducing Mean and Extreme Climates over West Africa

Diro, Gulilat Tefera, Intsiful, Joseph Daniel, Babalola, Toju Esther, Gbode, Imoleayo Ezekiel

2023

Overview

In situ data in West Africa are scarce, and reanalysis datasets could be an alternative source to alleviate the problem of data availability. Nevertheless, because of uncertainties in numerical prediction models and assimilation methods, among other things, existing reanalysis datasets can perform with various degrees of quality and accuracy. Therefore, a proper assessment of their shortcomings and strengths should be performed prior to their usage. In this study, we examine the performance of ERA5 and ERA-interim (ERAI) products in representing the mean and extreme climates over West Africa for the period 1981–2018 using observations from CRU and CHIRPS. The major conclusion is that ERA5 showed a considerable decrease in precipitation and temperature biases and an improved representation of inter-annual variability in much of western Africa. Also, the annual cycle is better captured by ERA5 in three of the region’s climatic zones; specifically, precipitation is well-reproduced in the Savannah and Guinea Coast, and temperature in the Sahel. In terms of extremes, the ERA5 performance is superior. Still, both reanalyses underestimate the intensity and frequency of heavy precipitations and overestimate the number of wet days, as the numerical models used in reanalyses tend to produce drizzle more often. While ERA5 performs better than ERAI, both datasets are less successful in capturing the observed long-term trends. Although ERA5 has achieved considerable progress compared to its predecessor, improved datasets with better resolution and accuracy continue to be needed in sectors like agriculture and water resources to enable climate impact assessment.

• Publisher: Science Press,Springer Nature B.V,Department of Meteorology and Climate Science,Federal University of Technology Akure,P.M.B.704 Ilesa-Owo Expressway,Akure,Ondo State 340420,Nigeria%Department of Water Resources Management and Agro-Meteorology,Federal University Oye-Ekiti,371104,Nigeria%Canadian Network for Regional Climate and Weather Processes,University of Quebec at Montreal,201 President-Kennedy Avenue,Montreal,QC H2X 3Y7,Canada%Division of Mitigation and Adaptation,Green Climate Fund,Incheon 22004,South Korea
• Subject: Accuracy / Annual variations / Atmospheric Sciences / Climate and Weather Extremes / Climatic extremes / Climatic zones / Datasets / Drizzle / Earth and Environmental Science / Earth Sciences / Geophysics/Geodesy / Impact assessment / Interannual variability / Mathematical models / Meteorology / Numerical models / Numerical prediction / Original Paper / Precipitation / Prediction models / Water resources / Wet days