Preprints
https://doi.org/10.5194/nhess-2023-147
https://doi.org/10.5194/nhess-2023-147
23 Aug 2023
 | 23 Aug 2023
Status: this discussion paper is a preprint. It has been under review for the journal Natural Hazards and Earth System Sciences (NHESS). The manuscript was not accepted for further review after discussion.

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.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.
Nele Tim, Birgit Hünicke, and Eduardo Zorita

Status: closed

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
    • AC1: 'Reply on RC1', Eduardo Zorita, 15 Nov 2023
  • RC2: 'Comment on nhess-2023-147', Anonymous Referee #2, 07 Sep 2023
    • AC2: 'Reply on RC2', Eduardo Zorita, 15 Nov 2023

Status: closed

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
    • AC1: 'Reply on RC1', Eduardo Zorita, 15 Nov 2023
  • RC2: 'Comment on nhess-2023-147', Anonymous Referee #2, 07 Sep 2023
    • AC2: 'Reply on RC2', Eduardo Zorita, 15 Nov 2023
Nele Tim, Birgit Hünicke, and Eduardo Zorita
Nele Tim, Birgit Hünicke, and Eduardo Zorita

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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.
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