On the question of the recovery of the rains in the West African Sahel

Various reports have suggested that there has been a recovery of the rainy season in Sahelian West Africa in recent years. In this study, rainfall time series for West Africa are updated to the year 2003 by using rainfall estimates from the Tropical Rainfall Measuring Mission (TRMM). Emphasis is on the period 1998-2003. Analyses include time series for eight zones, in the latitudes from 12 degrees N to 20 degrees N; maps of seasonal and August rainfall in these years; and various measures of the seasonal cycle. A comparison is made with the prolonged periods of wetter and drier conditions than prevailed earlier in the century: the extreme wet decade of the 1950s and the 30-year climatological normal for the very dry period 1968-97. Results show that there has been some recovery with respect to this very dry period. The recovery was generally weaker in August (which is generally the wettest month) than during the season as a whole. The recovery was most marked in the western Sahel. The exception was the northern-most zone (the Saharan margin, 18 20 degrees N), which remained relatively dry. In the three zones to the south seasonal totals exceeded the long-term mean in all years and conditions were comparable to or wetter than those occurring during the wet decade of the 1950s. The wettest years were 1998, 1999 and 2003. The results also suggest a limited recovery in the eastern Sahel/Soudan. Rainfall returned to pre-drought levels in the two southern-most Sahel zones (12-16 degrees N), but in the two northern zones (16-20 degrees N), the drought appears to have intensified. In the southern-most zone (the central Sahel, 12-14 degrees N), conditions in recent years seem to have been particularly favorable and comparable to the 1950s and 1960s. August trends were markedly similar to these seasonal trends. As in the western region, the wettest years were 1998, 1999 and 2003, but only 2000 was markedly drier than the other five. (c) 2005 Elsevier Ltd. All rights reserved.