Spatial patterns of seasonal scale trends in extreme hourly precipitation in South Africa

Hourly precipitation data from 1998 to 2007 spread across 102 stations in South Africa were analyzed for trends in extreme hourly precipitation events. The analyses were conducted at the seasonal scale for summer and winter for nine different variables. The results of our analysis showed predominantly positive trends during summer, with the strongest trends concentrated in the coastal areas in the southeast. The spatial variations in the trends were reversed during the winter season, with negative trends observed in the coastal areas and positive trends occurring in the interior. The summer patterns also overlap with areas experiencing overall increasing trends in annual extreme precipitation as well as a stronger diurnal cycle identified in recently published literature.

► Trends in extreme precipitation events during summer were predominantly positive across South Africa.
► The strongest positive trends were observed along the southeastern and western coasts.
► Neutral to weak positive trends were found to be scattered within small areas in the interior.
► During winter, the coastal areas experienced negative trends, with positive trends in the interior high altitude areas.
► Fewer variations in the winter due to large synoptic processes compared to localized convective processes in summer.