Interconnections between SST and Extreme Rainfall in the Gulf of Guinea

Abstract

The gulf of Guinea and West Africa is characterized by extreme precipitation accounting for intense flooding and related disasters. It has therefore become imperative to understand the role of SST anomaly and other physical mechanisms that drives for the spatio-temporal variability and predictability of extreme precipitation in the West Africa region. This study was conducted to examine the interconnections between large scale SST anomalies in extreme precipitation over the coast of Guinea. The study employed Regional climate model 4.7 , the Advanced Weather Research and forecasting model at 5km resolution and GIS software called ILWIS software (version 3.2 Academic) to quantify the influence of SST anomaly on the spatio-temporal variation of precipitation over the Guinean coast. A control simulation driven reanalysis and monthly SST data generated from the National Oceanic and Atmospheric Administration NOAA Optimum interpolation at 2⁰ intervals from long 10 °W, 8 °W, 6 °W, 4 °W,2 °W, 0°, 2 °E, 4 °E, 6 °E, and 8 °E, and latitudes 5 °N, 3 °N, 1 °N, 1 °S, 3 °S, and 5 °S. 10 °W, 8 °W, 6 °W, 4 °W, 2 °W, 0°, 2 °E, 4 °E, 6 °E, and 8 °E, and latitudes 5 °N, 3 °N, 1 °N, 1 °S, 3 °S, and 5 °S. The results obtained show that the SST in the GOG generally decreases westward and southward, while the reverse of the case holds for its variability values. Detailed observations show that the SST is generally below the latitudinal average and its variability values, above the latitudinal average mainly between longitudes 8 °W and 2 °E. The results also show that during the period of July-August September, the SST is anomalously colder between longitudes 8 °W and 2 °E and the West African coastal border and latitude 3 °N. This area was observed as constituting the area of the coastal upwelling. The intra-annual distribution of the SST, as evident along latitudes 3 °N and 5 °N, shows two main regimes and two transitional periods in between the regimes. The first regime is November to May, and the second, July to September. The first regime transits to the second during the month of June and the second back to the first, during the month of October. The comparative analysis of the first and second half of the period of study indicates that the SST of the GOG has undergone some warming over time. The comparison also shows that although the SST has generally risen, an area of relatively cool SST near the Guinea coast has expanded from longitudes 7 °W–0 °W to 8 °W–3 °E