Wet and dry spells within particularly wet and dry summers in the South African summer rainfall region

摘要: Atmospheric moisture transport over southern Africa and surrounding oceans is consid- ered during wet dry conditions the South African summer rainfall region. Wet syn- optic spells within austral summers are examined. A link between synoptic seasonal timescales investigated using statistics of spells. Dry exhibit divergent flux Africa, with inflow from mid-latitude ocean regions to south. Cyclonic features off east coast may exist attract away Africa. For spells, there tends be increased tropical or subtropical south- west Indian Ocean (SWIO), either associated ridging along a deep low interior. Seasonal modulations intensity heat Angola/Namibia appear important for influencing early (OND) late (JFM) This act as source temperate troughs their cloudbands that major synop- tic rain-producing systems. (dry) often southward (northward) shift strengthening (weakening) ITCZ southeastern found related distribution season, such wetter sea- sons tend have longer more intense rather than greater number