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 assi...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.展开更多
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)dyn...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.展开更多
文摘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.
基金funded by the National Ministry of High Education,Research and Technological Innovation of the Republic of Niger through the Scientific Research and Technological Innovation Support Funds(FARSIT).
文摘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.
