The Projected Changes of Precipitations over Niger Under the Scenarios RCP 4.5 and RCP 8.5

The socio-economic activities of Niger rely on agriculture which is strongly affected by changes in precipitation during the rainy season.The ultimate aim of this study is to assess the projected changes of precipitation over Niger under the Representative Concentration Pathways(RCP)scenarios 4.5(RCP 4.5)and RCP 8.5 using multi-RCM(Multi-Regional Climate)model approach.The observation data are from CHIRPS(Climate Hazards Group InfraRed Precipitation with Station)and the RCMs are from the SMHI(Swedish Meteorological and Hydrological Institute)model(RCA4)driven by ten(10)different GCMs(General Circulation Model)(e.g.,CCCma,CSIRO,ICHEC,IPSL,MIROC,MOHC-HadGEM2,MPI,NCC-NorESM1,NOOA,and NRCM)within the framework of CORDEX(Coordinated Regional Climate Downscaling Experiment)Africa experiment.The reference and projections periods in this study are respectively 1981-2005 for the present and 2011-2100 for the near,medium and far future divided into three periods,2011 to 2040(P1),2041 to 2070(P2)and 2071 to 2100(P3).The methodology used,consists of assessing the performance of the multi-RCMs of RCA4 model(with respect of CHIRPS)in simulating the precipitations changes by computing the spatial distribution and anomalies of precipitations;and their indices of RMSE(Root Mean Square Error),the bias,SPI(Standardized Precipitation Anomaly Index),correlation coefficient,statistical t-test,spatial evolution rate and the rate of temporal change.After the validation of the multi-RCMs RCA4 models,the ensemble mean of the models is used to assess the projected changes of precipitations over Niger in the future.The results show that most of the multi-RCMs capture the four climatic zone except for IPSL.While the ensemble mean of the models simulates(as compared to CHIRPS)more accurately the monthly,annual precipitations anomalies and their indices than individual’s models in the reference period,some RCMs(e.g.,CSIRO-IPSL and CCCma-HadGEM)poorly reproduce them.The projected changes of precipitations indicate for the scenario RCP 4.5 respectively a moderately surplus of precipitation years in the period P1 and moderately deficit years in the period P2 while the period P3 shows a small upward precipitation trend.In contrary,for the scenario RCP 8.5,all the three periods(P1,P2 and P3)indicate an intensification of precipitation leading to a longer wet period which may lead to extreme precipitations and flooding.Moreover,both scenarios have projected an increase of total monthly precipitation in May and September and a decrease in July and August respectively which will likely lead to an early onset and late cessation of the rainy season;and a shift of the peak of the rainy season.Therefore,this study shows the need of a monitoring system for the projected changes of precipitation in the near future to anticipate urgent action in wet/dry periods to adapt to a changing climate.