23 Aug 2023
 | 23 Aug 2023
Status: this preprint is currently under review for the journal NHESS.

Simulated rainfall extremes over southern Africa over the 20th and 21st centuries

Nele Tim, Birgit Hünicke, and Eduardo Zorita

Abstract. In Southern Africa, precipitation is a crucial variable linked to agriculture and water supply. In addition, extreme precipitation causes devastating flooding, and heavy rainfall events are a significant threat to the population in this region. We analyse here the spatial patterns of extreme precipitation and its projected changes in the future. We also investigate whether the Agulhas Current, a major regional oceanic current system, influences those events. For this purpose, we analyse simulations with the regional atmospheric model CCLM covering the last decades and the 21st century. The simulations are driven by atmospheric reanalysis and by two global simulations. The regional simulations display the strongest precipitation over Madagascar, the Mozambique channel, and the adjacent mainland. Extreme rainfall events are most intense over the mountainous regions of Madagascar and Drakensberg and the African Great Lakes. In general, extremes are stronger in the Summer Rainfall Zone than in the Winter Rainfall Zone.

Extremes are projected to become more intense over the South African coast in the future. For the KwaZulu-Natal Province, the heaviest rainfall event in the future is twice as strong as the strongest extreme simulated in the historical period and the recently observed disastrous extreme event in April 2022. The impact of the Agulhas Current System on strong rainfall events over the South African coast does not clearly appear in the simulations.

Nele Tim et al.

Status: open (until 04 Oct 2023)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on nhess-2023-147', Anonymous Referee #1, 28 Aug 2023 reply
  • RC2: 'Comment on nhess-2023-147', Anonymous Referee #2, 07 Sep 2023 reply

Nele Tim et al.

Nele Tim et al.


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Short summary
Our study analyses extreme precipitation over southern Africa in regional high-resolution atmospheric simulations of the past and future. We investigated heavy precipitation over Southern Africa, coastal South Africa, Cape Town, and the KwaZulu-Natal province in eastern South Africa. Coastal precipitation extremes are projected to intensify, double in intensity in KwaZulu-Natal, and weaken in Cape Town. Extremes are not projected to occur more often in the 21st century than in the last decades.