Relationship Between Tropical Atlantic Marine Heatwaves and Rainfall in West Africa During the Monsoon Period

The West African climate system is highly sensitive to oceanic conditions in the Gulf of Guinea (GG), where rising sea surface temperatures (SSTs) and marine heatwaves (MHWs) are emerging as key indicators of regional climate change. This study analyses the relationship between MHW during the monsoon period and rainfall in West Africa using 30‐year data (May–October) of daily SST and precipitation. Based on the SST dataset. MHW intensities allowed to delineate the oceanic zones of their occurrences. The results show that these events have enhanced over the last decade along the northern coast of the GG and at the equator. Different classes are defined in each oceanic area defined. The high intensities of the MHWs of the different classes are located in the upwelling zone along the northern coast of GG. The analysis of the cumulative annual rainfall shows that the wettest regions are situated in the western and eastern parts of the Guinean zone of West Africa. It’s interannual trend is not significant, even if there is a break in 2018. The first modes of the relationships between each class of MHWs and rainfall show significant correlations between MHWs and rainfall of the coastal area and in the Sahelian zone. Most of the MHWs at the northern coast of the GG and in the tropical Atlantic cold tongue area have a positive influence on rainfall. All MHW events associated with rainfall represent about half of the MHW events that occur at the northern coast of the GG. For the Atlantic cold tongue area, the percentage of MHW concomitant with rainfall is about two‐third. A rainfall deficit is observed in the Sahelian zone during MHW events. This indicates that the onset of a rainfall deficit north of 10°N and an excess to the south coincides with the warming of the surface waters of the GG. This study is a first step to understand the impact of MHWs on climate, and their relationships with weather catastrophic extreme events.