Large-scale conditions that result in wet summers over arid Western Southern Africa
type: CreativeWork
description: The summer (November-April) rainfall patterns across the western region of southern Africa are poorly understood compared to the rest of southern Africa. Although the western interior of southern Africa is considered mostly arid, it is prone to highly variable rainfall and flash floods, impacting vulnerable communities and unique ecosystems. The recent extreme rainfall during 2020/21 and 2021/22 have highlighted the impacts such wet summers can have on vulnerable communities. However, it is not only the rainfall patterns that are poorly understood but also the large-scale drivers that lead to wet conditions across the region. Using a combination of satellite-derived rainfall products and ERA5 reanalysis, this study highlights the complex factors leading to summers with extreme rainfall in this typically arid area over the period 1981-2022. In the analysis, it is highlighted that the wettest conditions typically occur during January to February (JF) and March to April (MA). Departing from traditional approaches, the analysis focuses on ND, JF, and MA to capture variations in circulation changes and rain-bearing system activity. JF stands out with higher rainfall amounts and more rainy days (>10mm), contributing significantly to the overall seasonal rainfall. The seasonal rainfall cycle peaks in February and March, with the rainy season typically spanning from November to April. Spatial distribution emphasizes the region's relative dryness compared to nearby areas, showcasing distinct seasonal fluctuations. Rainfall characteristics, including moderate and heavy rain days, exhibit temporal variability within the seasonal cycle. Furthermore, the significance of late summer rainfall in each bi-monthly period is highlighted. The analysis also highlights considerable interannual variability, with associations between rainfall and climate modes such as the El Niño-Southern Oscillation (ENSO) and the Southern Annular Mode (SAM). However, ENSO stands out as the main driver. T…
abstract: The summer (November-April) rainfall patterns across the western region of southern Africa are poorly understood compared to the rest of southern Africa. Although the western interior of southern Africa is considered mostly arid, it is prone to highly variable rainfall and flash floods, impacting vulnerable communities and unique ecosystems. The recent extreme rainfall during 2020/21 and 2021/22 have highlighted the impacts such wet summers can have on vulnerable communities. However, it is not only the rainfall patterns that are poorly understood but also the large-scale drivers that lead to wet conditions across the region. Using a combination of satellite-derived rainfall products and ERA5 reanalysis, this study highlights the complex factors leading to summers with extreme rainfall in this typically arid area over the period 1981-2022. In the analysis, it is highlighted that the wettest conditions typically occur during January to February (JF) and March to April (MA). Departing from traditional approaches, the analysis focuses on ND, JF, and MA to capture variations in circulation changes and rain-bearing system activity. JF stands out with higher rainfall amounts and more rainy days (>10mm), contributing significantly to the overall seasonal rainfall. The seasonal rainfall cycle peaks in February and March, with the rainy season typically spanning from November to April. Spatial distribution emphasizes the region's relative dryness compared to nearby areas, showcasing distinct seasonal fluctuations. Rainfall characteristics, including moderate and heavy rain days, exhibit temporal variability within the seasonal cycle. Furthermore, the significance of late summer rainfall in each bi-monthly period is highlighted. The analysis also highlights considerable interannual variability, with associations between rainfall and climate modes such as the El Niño-Southern Oscillation (ENSO) and the Southern Annular Mode (SAM). However, ENSO stands out as the main driver. T…
author: Kekana, Bohlale
language: en
keywords: Ocean, Atmosphere Science
date published: 2025
date modified: 2026-07-24T01:34:01Z
provider: University of Cape Town
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Department of Oceanography

PropertyValue
property ID: Handle
value: http://hdl.handle.net/11427/41632