Sea surface temperature patterns in the Gulf of Guinea: their implications for the spatio-temporal variability of precipitation in West Africa

摘要

This study examined the sea surface temperature (SST) patterns in the Gulf of Guinea (GOG) and discussed their implications for the spatio-temporal variability of precipitation in West Africa. The SST data spanning over 49 years (1950-1998) at 2° × 2° resolutions were sourced from the archive of the International Research Institute for climate prediction. The specific locations where data were collected to represent the GOG are longitudes 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.