Spatial Variation and Trend of Extreme Precipitation in West Africa and Teleconnections with Remote Indices

Abstract

Extreme precipitation is a great concern for West Africa country, as it has serious consequence on key socio-economic activities. We use high resolution data from the Climate Hazards Group InfraRed Precipitation Stations (CHIRPS) to determine the spatial variability, trend of 8 extreme precipitation indices in West Africa and their relationship to remote indices. Spatial variability of extreme is characterized by maximum precipitation over the orographic regions, and in southern Sahel. The trend analysis shows a decrease of dry condition in Sahel and Sahara, and an increase tendency of wet indices over western Sahel and southern Sahel. The correlation analysis reveals that extreme precipitation in Sahel is strongly teleconnected to the Eastern Mediterranean Sea (EMS), whereas western and western-north Sahel is associated with both Atlantic Meridional Mode (AMM), Maiden Julian Oscillation phase 8 (MJO8), El Niño 3.4 index (NINO.3.4), and Trans-Atlantic-Pacific Ocean Dipole Index (TAPODI) but with different characteristics or directions. Guinean coast extreme precipitation is highly associated with Atlantic zone 3 SST anomaly (ATL3), Northern Cold Tongue Index (NCTI), TAPODI but also with an opposite sign with NINO.3.4 and in somewhat with the MJO8.

Interannual Variability and Trends of Extreme Rainfall Indices over Benin

“…[17] also indicated significant downward trends in wet indices across the Volta Lake and over central portions of Ghana, while small upward trends were found over northern parts of Ghana. The trend analysis over West Africa [9] shows a decrease of dry conditions in Sahara and Sahel, whereas an increasing trend in wet conditions was observed over western and southern Sahel.…”

“…An overall intensification and a positive scaling signal with North Hemispheric temperature is identified in annual summer and winter single day to monthly maximum rainfall over Central Europe [15]. In West Africa, downward trends in dry conditions were found in Sahel and Sahara, while upward trends of wet indices were found over western and southern Sahel [9]. Ref.…”

“…[37] over Cameroon for SDII and P. In the northwestern area of Benin, there is sometimes high extreme rainfall because this region is a mountain region and therefore it is dominated by orographic precipitation. At a large scale, an upward trend pattern is detected from Sahel to the Gulf of Guinea coast in the West Africa for extreme rainfall intensity indices (P, SDII, RX1day and RX5day) with the highest values of intensity indices near highland regions [9]. The annual number of heavy wet days (R10) and very heavy wet days (R20) has the same spatial pattern over Benin.…”

“…Many studies have investigated the potential cause of extreme rainfall change over West Africa [9,17,44,45]. They state that West African extreme rainfall is highly influenced by the large scale ocean surface temperature and atmospheric conditions in the tropical Atlantic.…”

“…West Africa is particularly vulnerable to the impact of extreme rainfall events due to a constantly increasing population and a lack of adequate adaptation strategies [9]. As with all the West African countries, Benin is also vulnerable to extreme rainfall impact because its economy is based on rain-fed agriculture.…”