Weather and climate extremes, such as heat waves (HWs), have become more frequent due to climate change, resulting in negative environmental and socioeconomic impacts in many regions of the world. The high vulnerability of South African society to the impacts of warm extreme temperatures makes the study of the effect of climate change on future HWs necessary across the country. We investigated the projected effect of climate change on future of South Africa with a focus on HWs using an ensemble of regional climate model downscalings obtained from the Conformal Cubic Atmospheric Model (CCAM) for the periods 2010–2039, 2040–2069, and 2070–2099, with 1983–2012 as the historical baseline. Simulations were performed under the Representative Concentration Pathway (RCP) 4.5 (moderate greenhouse gas (GHG) concentration) and 8.5 (high GHG concentration) greenhouse gas emission scenarios. We found that the 30-year period average maximum temperatures may rise by up to 6 °C across much of the interior of South Africa by 2070–2099 with respect to 1983–2012, under a high GHG concentration. Simulated HW thresholds for all ensemble members were similar and spatially consistent with observed HW thresholds. Under a high GHG concentration, short lasting HWs (average of 3–4 days) along the coastal areas are expected to increase in frequency in the future climate, however the coasts will continue to experience HWs of relatively shorter duration compared to the interior regions. HWs lasting for shorter duration are expected to be more frequent when compared to HWs of longer durations (over two weeks). The north-western part of South Africa is expected to have the most drastic increase in HWs occurrences across the country. Whilst the central interior is not projected to experience pronounced increases in HW frequency, HWs across this region are expected to last longer under future climate change. Consistent patterns of change are projected for HWs under moderate GHG concentrations, but the changes are smaller in amplitude. Increases in HW frequency and duration across South Africa may have significant impacts on human health, economic activities, and livelihoods in vulnerable communities.

Globally, subtropical circulation in the lower troposphere is characterized by anticyclones over the oceans. Subtropical anticyclones locate over subtropical belts, modulating weather and climate patterns in those regions. The Mascarene High is an anticyclone located over the Southern Indian Ocean and has a vital role in weather and climate variability over Southern Africa. The warm Western Indian Ocean is a major source of moisture for the subcontinent also permitting tropical cyclone genesis. In this study, we review the dynamics of the Mascarene High, its interactions with the ocean, and its impact on weather and climate over Southern Africa. We also review studies on the evolution of subtropical anticyclones in a future warmer climate. The links between SST modes over the Indian Ocean and the strengthening and weakening of the Mascarene High have been demonstrated. One important aspect is atmospheric blocking due to the Mascarene High, which leads to anomalous rainfall and temperature events over the subcontinent. Blocking leads to landfall of tropical cyclones and slow propagation of cut-off lows resulting in severe weather and flooding over the subcontinent. Understanding how expansion of the Mascarene High due to warming will alter trade winds and storm tracks and change the mean climate of Southern Africa is crucial.

Extreme rainfall associated with mid-tropospheric cut-off low (COL) pressure systems affected the entire east coast of South Africa during April 2022, leading to flooding and destruction of homes, electricity power lines, and road infrastructure, and leaving 448 people confirmed dead. Therefore, this study investigated the evolution of the two COLs and their impacts, including the occurrence of extreme rainfall and cold weather over the southeast coast of the country. We analysed observed and reanalysis meteorological data and mapped areas at risk to impacts of flood hazards on the east coast of South Africa. Extreme rainfall (>500 mm) accumulated over 16 days was observed along the east coast, with the amount of rainfall progressively decreasing inland. We found that the rainfall associated with the first COL was significantly enhanced by the interactions between a strong low-level onshore airflow across the Agulhas Current and the coastal escarpment, resulting in deep convection and lifting. An unusual surface cyclone with tropical characteristics developed over the subtropical southwest Indian Ocean, driving onshore southeasterly winds which enhanced low-level convergence. Moreover, the flood risk results revealed that, amongst others, land cover/use (52.8%), elevation (16.8%) and lithology (15.5%) were the most important flood predictor variables in this study. Much of the study area was found to have very low (28.33%), low (31.82%), and moderate (21.66%) flood risk, whilst the high- and very-high-risk areas accounted for only 17.5% of the total land area. Nonetheless, the derived flood risk map achieved an acceptable level of accuracy of about 89.9% (Area Under Curve = 0.899). The findings of this study contribute to understanding extreme rainfall events and the vulnerability of settlements on South Africa’s east coast to flood risk, which can be used towards natural disaster risk reduction.

Climate change has increased the frequency of extreme weather events such as heavy rainfall leading to floods in several regions. In Africa, rural communities are more vulnerable to flooding, particularly those that dwell in low altitude areas or near rivers and those regions affected by tropical storms. This study examined flood vulnerability in three rural villages in South Africa’s northern Limpopo Province and how communities are building resilience and coping with the hazard. These villages lie at the foot of the north-eastern escarpment, and are often exposed to frequent rainfall enhanced by orographic factors. Although extreme rainfall events are rare in the study area, we analyzed daily rainfall and showed how heavy rainfall of short duration can lead to flooding using case studies. Historical floods were also mapped using remote sensing via the topographical approach and two types of flooding were identified, i.e., those due to extreme rainfall and those due to poor drainage or blocked drainage channels. A field survey was also conducted using questionnaires administered to samples of affected households to identify flood vulnerability indicators and adaptation strategies. Key informant interviews were held with disaster management authorities to provide additional information on flood indicators. Subsequently, a flood vulnerability index was computed to measure the extent of flood vulnerability of the selected communities and it was found that all three villages have a ‘vulnerability to floods’ level, considered a medium level vulnerability. The study also details temporary and long-term adaptation strategies/actions employed by respondents and interventions by local authorities to mitigate the impacts of flooding. Adaptation strategies range from digging furrows to divert water and temporary relocations, to constructing a raised patio around the house. Key recommendations include the need for public awareness; implementation of a raft of improvements and a sustainable infrastructure maintenance regime; integration of modern mitigations with local indigenous knowledge; and development of programs to ensure resilience through incorporation of Integrated Development Planning.

Mopani District Municipality in the northeast of South Africa is largely semi-arid and frequently affected by meteorological droughts. The recent 2015/16 event had devastating impacts on water levels, crop yields, livestock herds and rural livelihoods. We investigated the nature of the drought hazard; its impacts, including vulnerability of rural communities in Mopani District and adaptation strategies they have employed to cope with drought. A mixed methods approach with both quantitative and qualitative datasets was used. The district was divided into two distinct climatic areas: the drier eastern lowveld and the wetter western bushveld. Questionnaires were administered among community members whilst key informant interviews were conducted among relevant government and municipal officials. Climate data was used to characterize historical drought using a Standardized Precipitation and Evapotranspiration Index whilst vegetation anomaly maps were used to demonstrate impacts. Spatially distinct patterns of drought conditions were evident with harsh and dry conditions towards the east. It was found that nearly half the time there is some form of drought or another in the district mostly linked to the remote El Nino phenomenon. In several areas, rain-fed agriculture is no longer tenable, with a direct impact on rural livelihoods. A Household Vulnerability Index determined variable levels of vulnerability such that different strategies are employed to adapt to drought some of which cause environmental problems. Local government intervention strategies include supply of seeds and fertilisers, providing cheap fodder and supplying water using trucks. The findings of this study contribute to disaster risk reduction efforts in a region that is highly vulnerable to current and future climate-risks.

Satellite-derived rainfall and vegetation [normalized difference vegetation index (NDVI)] data for the period 1981–2000 are used to reveal spatial and temporal interrelationships via principal component analysis. The unimodal seasonal cycle peaks in austral summer over the Zambezi Valley and interior plateau. Spectral analysis indicates major cycles of intraseasonal rainfall events at ∼20 and 40 days in response to atmospheric wave forcing that is partially phase locked to the annual cycle. The spatial loadings exhibit a “center of action” along the eastern edge of the Kalahari (±23°E), extending from the western Zambezi toward central South Africa, spanning 20° of latitude. The loading pattern is consistent with tropical–temperate troughs and associated northwest (NW) cloud bands. Twenty-day rainfall oscillations occur over the Agulhas Current and Angola, hence NW cloud bands are a slower terrestrial harmonic of the faster modes at either end. NDVI also exhibits intraseasonal cycles operating near 40 days with spatial loadings collocated with the slow rainfall mode at a 10–20-day lag. It is postulated that an earlier rainfall event and subsequent “greening” results in a moisture flux that promotes the next rainfall event. This is reflected in a composite analysis of low-level velocity potential. The vegetation draws airflow toward itself in a self-sustaining way.