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

Abstract

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 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-AugustSeptember, 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.

Evaluation of the ECMWF Sub-seasonal to Seasonal Precipitation Forecasts during the Peak of West Africa Monsoon in Nigeria

“…On the contrary, the sign-test for synchronization returns a p > 0.5, i.e., statistically not significant; implying that correct SST forecasts over GoG may be due to chances. Since SST conditions over GoG directly modulates rainfall patterns over Nigeria (Lawal, 2015), Odekunle and Eludoyin (2008) are of the opinion that underestimation of SST anomalies by models, over GoG, may be one of the reasons why models underestimate rainfall accumulation over Guinea Area (latitude 5-8 • N).…”

“…Few of these, discussed in this study, are the El Nino Southern Oscillation (ENSO; Latif and Grotzner, 2000;Camberlin et al, 2001;Newman et al, 2003), the Inter-Tropical Discontinuity (ITD; Grist and Nicholson, 2001;Redelsperger et al, 2002;Omotosho and Abiodun, 2007), thermal lows (Parker et al, 2005;Lavaysse et al, 2006Lavaysse et al, , 2009Lavaysse et al, , 2010, African Easterly Jet (AEJ; Diedhiou et al, 1998;Grist and Nicholson, 2001;Afiesimama, 2007), and the sea surface temperature (SST) anomalies over the Gulf of Guinea (GOG; Omotosho and Abiodun, 2007;Odekunle and Eludoyin, 2008).…”

“…This makes the moisture laden southwesterly wind more buoyant in terms of moisture and energy (Odekunle and Eludoyin, 2008). The energized wind is capable of dynamically pushing the ITD deeply into the northern end of the country, thereby resulting in above-normal rainfall (Omotosho and Abiodun, 2007), especially along the coast.…”

Seasonal evapotranspiration signatures under a changing landscape and ecosystem management in Nigeria: Implications for agriculture and food security

“…3) . One point worth mentioning is that agriculture in this densely populated zone is rainfed, with the land-cover and surface albedo changing as a result of unsustainable food production systems, deforestation and climate change evidenced by increasing rainfall variability (UNEP, 2007;Odekunle and Eludoyin, 2008;Salako, 2008). For the southwest geopolitical zone of Nigeria (Fig.…”

The Late Onset of the 2015 Wet Season in Nigeria

“…Figures 13.1d,e show that the observed SSTs (www.esrl.noaa.gov/psd/data /gridded/data.kaplan_sst.html; Kaplan et al 1998;) over the Gulf of Guinea were warmer than normal during April-May 2015. Under these warmer-thannormal SST conditions, it should have been possible to advect sufficient moisture to support precipitation (Zheng et al 1999;Odekunle and Eludoyin 2008). It would also be expected that the moisture laden southwesterly trade winds would have become more energized, buoyant, and capable of dynamically pushing the ITD deeply into the northern end of the country, thereby resulting in above-normal rainfall both at the coastal and inland parts of the country (Omotosho and Abiodun 2007).…”