An Overview of the Swell Dynamics and Their Implications over Africa: Significance to Climate Change and Forcing

There is a growing interest in climate dynamics as the quantity and quality of new observational and theoretical applications are increasing. The ideas involved in understanding large-scale atmosphere-land-ocean dynamics and their interactions continue to hold special fascination because of their central importance for both theoretical and practical applications. This paper presents a theoretical assessment of the African swell dynamics imploring atmospheric formulation. Africa exhibits substantial inter-annual and inter-decadal climatic variability due to cyclone activity, storm surges and sea waves. Most of these surges and corresponding swell trains form over the tropical environment as easterly waves propagate westward across the Indian Ocean primarily between 10° and 20° S, termed source region. Localized sea surface temperatures (SSTs) and ocean upwelling play a vital role to provide moist enthalpy to power the surges. Also, multi-decadal variations in major wave activity are associated with SST changes in the Atlantic because tropical North Atlantic correlates positively with major hurricane activity. A key remote factor is temperature variability in the central and eastern equatorial Pacific associated with El Niño Southern Oscillation. The continuous erosion, perennial ocean surges, coastal swells and associated flooding due to the wave energy and its pounding effect are of great concern. Just like in most parts of the world where development of these systems is critical, they need to be closely watched particularly over southern Africa.