Rainfall analysis of the sahelian drought in the gambia

Abstract

Using rainfall data from five stations in The Gambia, it is shown that there has been a very marked decrease in annual rainfall over the last thirty years. This decrease is thought to be due to a reduction in the number of rain-producing synoptic situations rather than a decrease in intensity of rainfall.Using monthly data for the five stations and decadal and daily data for one station, it is demonstrated that the characteristics of the rainfall season have varied systematically over the years. Although the length of the season is virtually unaltered there is a marked reduction of rainfall in the middle of the season, so that there is a tendency towards bimodality, which could have serious consequences for rain-fed agriculture.

Changing patterns of rain-days in Nigeria

“…For Sahelian West Africa, Dennett et al (1985) reported a significant decrease in August and September rainfall amounts for the period 1941-1983 while Hutchinson (1985) also reported a similar result for the Gambia based on data analysed for the period, 1941-1982. However, it has been shown in this study that the decline in rainfall-producing situations represented by rain-days has affected all months of the Sahelian rainy season in Nigeria -July to October -from 1939 to 1985.…”

“…Although the trends in climatic data are seldom linear (Mitchell et al 1966), the linear regression method has been used to search for trends in many climatic time series (e.g. Ayoade 1973;Hutchinson 1985;Subbaramayya and Bhanu Kumar 1987). In testing for non-randomness in a trend, Mitchell et al (1966) suggested the use of either Mann-Kendall ('r) or Spearman (rs) rank statistics.…”

“…Studies of long-term variability of annual fainfall (Lamb 1982;Nicholson 1983), of annual and rainy season monthly rainfalls (Dennett et al 1985;Hutchinson 1985) and of changing spatial pattern of annual and rainy season monthly rainfalls (Gregory 1983) have all indicated a long run of dry years for sub-Saharan West Africa dating back to the 1940s. Such a consistent decline in rainfall totals for the annual and monthly periods could result from a consistent decrease in the daily intensity of rain storms or it could be due to a progressive decrease in the frequency of rain-producing situations.…”

Towards a wetter Sudano‐Sahelian ecological zone in twenty‐first century Nigeria

“…Short-term and long-term trends that recur regularly can thus be referred to as shortterm and long-term periodicities, respectively. A review of the literature indicates apparent evidence of rainfall trends and periodicities in West Africa (Hutchinson, 1985;Adejuwon et al, 1990;Folland et al, 1991).…”

Identification of and Response to Drought by Local Communities in Fulladu West District, the Gambia

“…The climate of the area shows considerable variability not only in annual rainfall, but also in the timing of the onset and close of the rainy season (Anyadike, 1993;Hutchinson, 1985;Department of Water Resources Records, 1950-90). It has experienced recurrent and increasingly frequent agricultural droughts during much of the 1970s and 1980s.…”