Could ERA5 Deliver Better Climate Services Than ERA-Interim over the West African Sahel Region?

Our paper assessed the improvement performance of the reanalysis (ERA5) compared to ERAI (ERA-Interim) both from the ECMWF (European Center for Medium-Range Weather Forecast) in representing the WAM (West African Monsoon) dynamic. Our aim is to evaluate the reliability of ERA5 to deliver better climate services than ERAI in the West African Sahel region. Two complementary observational databases namely the CRU (Climate Research Unit) and the GPCC (Global Precipitation Climatology Center) data are used to evaluate precipitation and temperature representation by the two reanalysis. Otherwise, the representation of some major features of the WAM system, such as the SHL (Saharan Heat Low), the AEJ/TEJ (African and Tropical Easterly Jets) was assessed using the two reanalysis data. The obtained results show a better representation of the seasonal accumulated precipitation and average temperature by ERA5 compared to ERAI with higher spatial correlation and lower bias relative to the observations. Furthermore, ERAI appears to be rainier than ERA5 but ERA5 produces more heavy rainfall days. During the period of intense monsoon, the frequency of the SHL is higher for ERAI which would favor intensification of monsoon inflow and depth. The lower SHL frequency observed in the ERA5 could explain the observed weakening intensity of AEJ which is favorable for moist conditions over the Sahel. These findings confirm the progress made by ERA5 compared to ERAI in representing the WAM dynamic and demonstrate its reliability for delivering better climate services over the West African Sahel.