Temporal changes in seasonal precipitation over the Sahara Desert from 1979 to 2016

摘要

Rainfall variability dominates livelihoods in all countries of Saharan Africa.To better understand the processes involved in Sahara precipitation changes,we used the Global Precipitation Climatology Center(GPCC)dataset to examine dry and wet seasonal trends in the Sahara region from 1979 to 2016.We also used the European Centre for Medium-Range Weather Forecasts(ECMWF)to evaluate the general atmospheric circulation associated with seasonal change of Sahara precipitation.The Mann-Kendall test and Theil sens'slope estimator methods were adopted to test and estimate the significance and weight of precipitation trend,respectively.The results revealed that Sahara precipitation has increased significantly.The seasonal evaluation shows a positive trend of 0.42 mm/decade and 1.43 mm/decade in JAS(June,August,and September)seasons for the northern and southern Saharan Desert,respectively.Moreover,the JFMA(January,February,March,and April)period shows a negative trend but not statistically significant.An examination of the general circulation and moisture transport changes suggested an increase of rainfall in southern Sahara.The wet period is also driven by northward penetration of moisture originating from the Sahel region,African Easterly Jet(AEJ),and weakening in the upper tropospheric zonal wind.Summer rainfall has also been likely associated with positive anomalies of sea surface temperature(SST)in the North Tropical Atlantic(NTA)and the Mediterranean Sea.