An Analysis of Recent Rainfall Conditions in West Africa, Including the Rainy Seasons of the 1997 El Niño and the 1998 La Niña Years

Abstract

This article examines recent rainfall conditions throughout the Sahel and in other parts of West Africa in detail and presents an overview of changes in rainfall on timescales of decades for Africa as a whole. In West Africa, there has been a pattern of continued aridity since the late 1960s that is most persistent in the more western regions. Some recovery occurred in the easternmost sectors during the 1990s, with rainfall in some years being near or just above the long-term mean. Dry conditions continued during 1997, but that year was not unusually dry compared to others of the last two decades. Hence, it appears that the 1997 El Niño did not have a large impact in the region. A preliminary analysis suggests that in 1998 rainfall was still below the long-term mean in most of the Sahel, but the central Sahel of Niger experienced localized flooding due to high rainfall in September. Throughout the region, the wettest years of the last decades were 1978, 1988, 1994, and possibly 1998, but conditions in even these years exceeded the long-term mean in only a few sectors. A long-term change in rainfall has occurred in the semiarid and subhumid zones of West Africa. Rainfall during the last 30 yr (1968?97) has been on average some 15% to 40% lower than during the period 1931?60. A similar but smaller change has occurred in semiarid and subhumid regions of southern Africa.