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On the Causes of the Minor Dry Season over the Coastal Region of the Northern Gulf of Guinea

DOI: 10.4236/acs.2018.82009, PP. 121-133

Keywords: Dry Season, West African Monsoon, Gulf of Guinea, Coastal Upwelling, Convective Rainfall

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Along the littoral shelf of northern coast of the Gulf of Guinea (GG), a minor dry season of the rainfall regime is concomitantly observed with the occurrence of a major coastal upwelling in July-August-September (JAS). It was then supposed that this upwelling drives that minor dry season. But no previous studies have tried to understand this minor dry season and, this study is the first focusing on this question. The investigations undertaken to explain this dry season on the Ivorian littoral shelf with the ERA-Interim data from the European Centre for Medium Range Weather Forecasts over the 1980-2016 period have shown that the minor dry season is driven by the Northward migration of the Inter Tropical Convergence Zone (ITCZ) during this period and, enhanced by the occurrence of the major coastal upwelling of the northern GG at the same time. These two phenomena interact as follow: i) the ITCZ is located in JAS far in the north cutting off convective processes along the coast, ii) the air on the coastal region is poor in humidity, iii) the air temperature on the bordering region of the GG is cooled by the coastal upwelling to value less than 26°C and not favorable for providing convection.


[1]  Sultan, B. and Janicot, S. (2000) Abrupt Shift of the ITCZ over West Africa and Intra-Seasonal Variability. Geophysical Research Letters, 27, 3353-3356.
[2]  Le Barbé, L., Lebel, T. and Tapsoba, D. (2002) Rainfall Variability in West Africa during the Years 1950-1990. Journal of Climate, 15, 187–202.<0187:RVIWAD>2.0.CO;2
[3]  Gu, G. and Adler, R.F. (2004) Seasonal Evolution and Variability Associated with the West African Monsoon System. Journal of Climate, 17, 3364-3377.<3364:SEAVAW>2.0.CO;2
[4]  Hagos, S.M. and Cook, K.H. (2007) Dynamics of the West African Monsoon Jump. Journal of Climate, 20, 52-64.
[5]  Thorncroft, C.D., Nguyen, H., Zhang, C. and Peyrillé, P. (2011) Annual Cycle of the West African Monsoon: Regional Circulations and Associated Water Vapour Transport. Quarterly Journal of the Royal Meteorology Society, 137, 129-147.
[6]  Kouadio, Y., Ochou, D.A. and Servain, J. (2003) Tropical Atlantic and Rainfall Variability in Cote d’Ivoire. Geophysical Research Letters, 30, 1-4.
[7]  Yoroba, F., Diawara, A., Kouadio, K.Y., Schayes, G., Assamoi, A.P., Kouassi, K.B., Kouassi, A.A. and Toualy, E. (2011) Analysis of the West African Rainfall Using a Regional Climate Model. International Journal of Environmental Sciences, 1, 1335-1349.
[8]  Cautenet, S. and Rosset, R. (1989) Numerical Simulation of Sea Breezes with Vertical wind Shear during Dry Season at Cape of Three Points, West Africa. Monthly Weather Review, 117, 329-339.<0329:NSOSBW>2.0.CO;2
[9]  Caniaux, G., Giordani, H., Redelsperger, J-L., Guichard, F., Key, E. and Wade, M. (2001) Coupling between the Atlantic Cold Tongue and the West African Monsoon in Boreal Spring and Summer. Journal of Geophysical Research, 116, C04003.
[10]  Wang, G. and Eltahir, E.A.B. (2000) Ecosystem Dynamics and the Sahel Drought. Geophysical Research Letters, 27, 795-798.
[11]  Fontaine, B., Trazaska, S. and Janicot, S. (1998) Evolution of the Relationship between Near and Global and Atlantic SST Modes and the Rainy Season in West Africa: Statistical Analyses and Sensitivity Experiments. Climate Dynamics, 14, 353-368.
[12]  Tompkins, A.M. (2001) On the Relationship between Tropical Convection and Sea Surface Temperature. Journal of Climate, 14, 633-637.<0633:OTRBTC>2.0.CO;2
[13]  Nicholson, S.E. and Grist, J.P. (2001) A Conceptual Model for Understanding Rainfall Variability in the West African Sahel on Interannual and Interdecadal Timescales. International Journal of Climatology, 21, 1733-1757.
[14]  Diedhiou, A., Janicot, S., Viltard, A. and De Felice, P. (1998) Evidence of Two Regimes of Easterly Waves over West Africa and Tropical Atlantic. Geophysical Research Letters, 25, 2805-2808.
[15]  Bakun, A. (1987) The Guinea Current Upwelling. Nature, 271, 147-150.
[16]  Picaut, J. (1983) Propagation of the Seasonal Upwelling in the Eastern Equatorial Atlantic. Journal of Physical Oceanography, 13, 18-37.<0018:POTSUI>2.0.CO;2
[17]  Toualy, E., Stanojevic, G., Kouadio, K.Y. and Aman, A. (2012) Multi-Decadal Variability of Sea Surface Temperature in the Northern Coast of Gulf of Guinea. Asian Journal of Applied Sciences, 5, 552-562.
[18]  Ali, K.E., Kouadio, K.Y., Zahiri, E.P., Aman, A., Assamoi, A.P. and Bourles, B. (2011) Influence of the Gulf of Guinea Coastal and Equatorial Upwellings on the Precipitations along Its Northern Coasts during the Boreal Summer Period. Asian Journal of Applied Sciences, 4, 271-285.
[19]  Chilton, D.B., Esbensen, S.K., Schlax, M.G., Thum, N., Freilich, M.H., Wentz, F.J., Gentemann, C.L., McPhaden, M.J. and Schopf, P.S. (2001) Observations of Coupling between Surface Wind Stress and Sea Surface Temperature in the Eastern Tropical Pacific. Journal of Climate, 14, 1479-1498.<1479:OOCBSW>2.0.CO;2
[20]  Wallace, J.M., Mitchell, T.P. and Deser, C. (1989) The Influence of Sea Surface Temperature on Surface Wind in the Eastern Equatorial Pacific: Seasonal and Interannual Variability. Journal of Climate, 2, 1492-1499.<1492:TIOSST>2.0.CO;2
[21]  Semedo, A., Suselj, K., Rutgersson, A. and Sterl, A. (2011) A Global View on the Wind Sea and Swell Climate and Variability from ERA-40. Journal of Climate, 42, 1461-1479.
[22]  Dee, D.P., Uppala, S.M., Simmons, A.J., Berrisford, P., Poli, P., Kobayashi, S., Andrae, U., Balmaseda, M.A., Balsamo, G., Bauer, P., Bechtold, P., Beljaars, A.C.M., Van de Berg, L., Bidlot, J., Bormann, N., Delsol, C., Dragani, R., Fuentes, M., Geer, A.J., Haimberger, L., Healy, S.B., Hersbach, H., Holm, E.V., Isaksen, L., Kallberg, P., Kohler, M., Matricardi, M., McNally, A.P., Monge-Sanz, B.M., Morcrette, J.J., Park, B.K., Peubey, C., De Rosnay, P., Tavolato, C., Thepaut, J.N. and Vitart, F. (2011) The ERA-Interim Reanalysis: Configuration and Performance of the Data Assimilation System. Quarterly Journal of the Royal Meteorological Society, 137, 553-597.
[23]  Dee, D.P. and Uppala, S. (2009) Variational Bias Correction of Satellite Radiance Data in the ERA-Interim Reanalysis. Quarterly Journal of the Royal Meteorological Society, 135, 1830-1841.
[24]  De Leeuw, J., Methven, J. and Backburn, M. (2014) Evaluation of ERA-Interim Reanalysis Precipitation Products Using England and Wales Observations. Quarterly Journal of the Royal Meteorological Society, 141, 798-806.
[25]  Pfeifroth, U., Mueller, R. and Ahrens, B. (2013) Evaluation of Satellite-Based and Reanalysis Precipitation Data in the Tropical Pacific. Journal of Applied Meteorology and Climatology, 52, 634-644.
[26]  Di Giuseppe, F., Molteni, F. and Dutra, E. (2013) Real-Time Correction of ERA-Interim Monthly Rainfall. Geophysical Research Letters, 40, 3750-3755.
[27]  Huffman, G.J., Adler, R.F., Arkin, P., Chang, A., Ferraro, R., Gruber, A., Janowiak, J., McNab, A., Rudolf, B. and Schneider, U. (1997) The Global Precipitation Climatology Project (GPCP) Combined Precipitation Dataset. Bulletin of the American Meteorological Society, 78, 5-20.<0005:TGPCPG>2.0.CO;2
[28]  Huffman, G.J., Adler, R.F., Bolvin, D.T. and Gu, G. (2009) Improving the Global Precipitation Record: GPCP Version 2.1. Geophysical Research Letters, 36, LI17808.
[29]  Adler, R.F., Huffman, G.J., Chang, A., Ferraro, R., Xie, P.P., Janowiak, J., Rudolf, B., Schneider, U., Curtis, S., Bolvin, D., Gruber, A., Susskind, J., Arkin, P. and Nelkin, E. (2003) The Version-2 Global Precipitation Climatology Project (GPCP) Monthly Precipitation Analysis (1979-Present). Journal of Hydrometeorology, 4, 1147-1167.<1147:TVGPCP>2.0.CO;2


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