HR: 16:40h
AN: A34A-03    [Abstracts]
TI: Land-Ocean Coupling as a Mechanism for Interannual Variability Over West Africa
AU: * Nicholson, S E
EM: sen@met.fsu.edu
AF: Florida State University, Dept. of Meteorology Florida State Univ., Tallahassee, FL 32306-4520 United States
AU: Barcilon, A
EM: barcilon@met.fsu.edu
AF: Florida State University, Dept. of Meteorology Florida State Univ., Tallahassee, FL 32306-4520 United States
AU: Grist, J P
EM: jeremygrist@yahoo.co.uk
AF: Southhampton Oceanography Centre, University of Southampton Waterfront Campus,, Southhampton, SO14 3ZH United Kingdom
AB: The development of the rainy season over West Africa is strongly influenced by sea-surface temperatures over the Gulf of Guinea. The connection is linked to a dynamical process that modulates the southwesterly flow over the tropical Atlantic and the Guinea Coast and thereby determines the position of the African Easterly Jet (AEJ) over the continent. Superimposed upon this is the influence of the Tropical Easterly Jet (TEJ), which varies greatly in intensity and location over West Africa. Wet years in the semi-arid zone of West Africa (the Sahel-Soudan) are linked to a strong westerly jet in the lower troposphere, the effect of which is to weaken the AEJ and displace it northward. Along with the northward displacement, strong convective activity is also displaced into the higher latitudes of the semi-arid zone. A strong TEJ in wet years works in tandem with these other systems to enhance convection. During dry years the westerly jet does not develop and the AEJ is stronger, but it lies along a more southward track. This displaces the maximum convective activity equatorward and reduces its intensity, producing abnormally dry conditions in the semi-arid zone. The location and weakened intensity of the TEJ further reduce convection. A comparison with dynamic processes at similar latitudes over Central Africa, where land-ocean contrast plays no role, shows significant differences in the factors regulating precipitation and in the nature of interannual variability. These scenarios described above explain decadal scale variations in precipitation over West Africa.
DE: 3339 Ocean/atmosphere interactions (0312, 4504)
DE: 3309 Climatology (1620)
DE: 1812 Drought
DE: 1854 Precipitation (3354)
DE: 1620 Climate dynamics (3309)
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting