Interannual variability of African wave activity in a general circulation model

• Published in: International journal of climatology Vol. 18; no. 12; pp. 1305 - 1323
• Main Authors: Thorncroft, C. D., Rowell, D. P.
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01-10-1998; Wiley
• Subjects: African wave activity; Earth, ocean, space; Exact sciences and technology; External geophysics; general circulation model; General circulation. Atmospheric waves; interannual variability; Meteorology; West Africa; Africa; Rain; Seasonal anomaly; General circulation models; Intraseasonal variation; Correlation analysis; Easterly wave; Atmospheric wave; Interannual variation
• ISSN: 0899-8418; 1097-0088
• DOI: 10.1002/(SICI)1097-0088(1998100)18:12<1305::AID-JOC281>3.0.CO;2-N

African easterly waves are an important part of the tropical climate, impacting on daily rainfall patterns as well as being the precursors for most Atlantic hurricanes. Despite their importance, the interannual variability of these waves is not well known or understood. This study shows that a general circulation model exhibiting a realistic amplitude of interannual seasonal mean rainfall variability in the tropical west African region, exhibits marked interannual variability in African easterly wave activity. Seasonal anomalies of this wave activity have been shown to be homogeneous over tropical north west Africa and are positively correlated with (i) the seasonal mean rainfall and associated convective heating in the Guinea Coastal region; and (ii) the strength of the easterlies in the region of and to the north of the African easterly jet. It is further concluded that the intraseasonal variations of African easterly jet instability must be considered for a more complete understanding of interannual African easterly wave variability. © 1998 Royal Meteorological Society