Dynamics of the Conformal-Cubic Atmospheric Model projected climate-change signal over southern Africa

摘要

The projected climate-change signal in simulations by the Con formal-Cubic Atmospheric Model (CCAM) over southern Africa is presented, with particular emphasis on the projected changes in circulation over the region. Current (1975-2005) and future (2070-2100; A2 scenario) climate simulations are used for this purpose. In the austral winter of the future climate, frontal rain bands are displaced to the south as a result of the subtropical high-pressure belt intensifying to the south of the subcontinent. In spring and autumn, mid- and upper-level highs are simulated to become more prominent over the eastern and central parts of southern Africa. The enhanced subsidence associated with these systems results in generally lower rainfall totals over much of the south-eastern subcontinent. To the north of these highs, enhanced westward moisture advection contributes to increased rainfall totals over northern Mozambique, whilst along the western periphery of the anomalously strong highs, enhanced southward moisture advection results in higher rainfall totals over Namibia, Botswana and the central and western interior of South Africa. In mid-summer, the Indian Ocean High (IOH) is simulated to intensify most over the south-western Indian Ocean (IO). This seemingly results in the more frequent occurrence of the cloud bands that constitute the South Indian Convergence Zone (SICZ) over the Southeastern subcontinent - resulting in generally wetter conditions over this region.