Seasonal and year-to-year variations of rainfall in the Sahara desert region based on TRMM PR data

[1] Using TRMM (Tropical Rainfall Measuring Mission) precipitation radar data and NCEP reanalysis data, this paper investigates seasonal and year-to-year variations of rainfall over the Sahara desert (20degrees -30degreesN, 10degreesW -30degreesE) from 1998 to 2001. Most rainfall occurs in the northern (southern) part from October to April (July to September). From May to June, precipitation occurs in both areas. Seasonal migration of the main rainfall area results from changes of rainfall types associated with the change of zonal wind and specific humidity in Northern Africa. While the mid-latitude westerly at 200 hPa is dominant when rainfall occurs in the northern part, the African Easterly Jet (AEJ) at 600 hPa and the lower layer moisture affect rainfall in the southern part. Year-to-year rainfall amount variations are also related to zonal wind changes, such as southward migration of the westerly and northward migration of the AEJ.