Interannual Variability of Rainfall over the West Africa Sahel

Aichetou Dia-Diop,Eric Efon,Andre Lenouo,Bouya Diop,Sinclaire Zebaze,Malick Wade,Rinelle Ngongang Djiondo

doi:10.4236/gep.2020.83007

Abstract

Interannual variability of the precipitation over West Africa Sahel is analyzed based on 32 years (1979-2010) from monthly and daily database of the Global Precipitation Climatology Project (GPCP). In this region, we found that there is a link between the West Africa Monsoon (WAM) and the daily means of the precipitation in the summer, unseasonal rains can occur in the transition seasons and even in the heart of the dry season. Rainfall is the most important element for agro-pastoral activities in this region. The 850-hPa wind and wind divergence structure show a maximum convection over Mountain region (Fouta-Djalon and Mont-Cameroon) which corresponds to the high precipitation and OLR observed in these regions. The trend and empirical orthogonal function (EOF) of the precipitation are presented, including the mid-July variability of the precipitation. The dominant EOF of GPCP precipitation accounts for around 25.3% of the variance with slightly large amplitude in the north while relatively small in the equatorial band respectively. The second and third EOF which accounts for 20.5% and 14%, describes a longitudinal contrast with a zonal gradient.

Highlights

Sahel is an area of semi-arid expanse of grassland, shrubs and small thorny trees found in Southern Sahara Desert (Nicholson, 2013)
The 850-hPa wind and wind divergence structure show a maximum convection over Mountain region (Fouta-Djalon and Mont-Cameroon) which corresponds to the high precipitation and outgoing longwave radiation (OLR) observed in these regions
The 850-hPa wind and wind divergence structure show a maximum convection over Mountain regions (i.e. Fouta-Djalon and Mont-Cameroon) which corresponds to the high precipitation and OLR observed in these regions

Summary

Introduction

Sahel is an area of semi-arid expanse of grassland, shrubs and small thorny trees found in Southern Sahara Desert (Nicholson, 2013). 5000 km across Africa from east to west and from the Sahara to the humid savannah at roughly 10 ̊N, even though more precisely, “Sahel” applies to a smaller region between latitudes 14 ̊N and 18 ̊N. Sahel includes the countries like Sudan, Chad, Mali, Senegal, Niger, Mauritania, Burkina Faso (northern part), Nigeria (northern part). Most of the local population in this region live in rural areas and practise agriculture. Variabilities of climatic parameters are of great importance to the region

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Conclusion