To issue warnings of thunderstorms, which have the potential for severe weather elements such as heavy rainfall and hail, is a task of all weather services. In data sparse regions, where there is no or limited access to expensive observation systems, satellite data can provide very useful information for this purpose. The Nowcasting Satellite Application Facility in Europe developed software to identify and track rapidly developing thunderstorms (RDT) using data from the geostationary Meteosat Second Generation satellite. The software was installed in South Africa and tested over the South African as well as the southern African domain. The RDT product was validated by means of 20 case studies. Over the South African region, validation was done by means of visual comparison to radar images as well as in a quantitative manner against the occurrence of lightning. Visual comparisons between the RDT product and images from satellite data as well as the occurrence of heavier rainfall were done over areas outside South Africa. Good correlations were found between the identified storms and the occurrence of lightning over South Africa. Visual comparisons indicated that the RDT software can be useful over the southern African domain, where lightning and radar data are not available. Very encouraging results were obtained in the 20 case studies. The RDT software can be a valuable tool for general and aviation forecasters to warn the public of pending severe weather, especially in areas where other data sources are absent or not adequate.

Severe weather events associated with strong winds and flooding can cause fatalities, injuries and damage to property. Detailed and accurate weather forecasts that are issued and communicated timeously, and actioned upon, can reduce the impact of these events. The responsibility to provide such forecasts usually lies with government departments or state-owned entities; in South Africa that responsibility lies with the South African Weather Service (SAWS). SAWS is also a regional specialised meteorological centre and therefore provides weather information to meteorological services within the Southern African Development Community (SADC). We evaluated SAWS weather information using near real-time observations and models on the nowcasting to short-range forecasting timescales during two extreme events. These are the Idai tropical cyclone in March 2019 which impacted Mozambique, Zimbabwe and Malawi resulting in over 1000 deaths, and the floods over the KwaZulu-Natal (KZN) province in April 2019 that caused over 70 deaths. Our results show that weather models gave an indication of these systems in advance, with warnings issued at least 2 days in advance in the case of Idai and 1 day in advance for the KZN floods. Nowcasting systems were also in place for detailed warnings to be provided as events progressed. Shortcomings in model simulations were shown, in particular on locating the KZN flood event properly and over/underestimation of the event. The impacts experienced during the two events indicate that more needs to be done to increase weather awareness, and build disaster risk management systems, including disaster preparedness and risk reduction.

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Nitrogen oxides (NOx = NO + NO2) are toxic air pollutants and play a significant role in tropospheric chemistry. Global NOx hotspots are the industrialised regions of the USA, Europe, Middle East, East Asia and eastern parts of South Africa. Lightning is one of the many natural and anthropogenic sources of NOx to the troposphere. It plays a role in the formation of particulate matter and tropospheric ozone, which are both linked to harmful health and climate effects. The discourse on NOx over the southern African continent has mainly focused on anthropogenic sources. However, lightning is known to be a main source of tropospheric NOx globally. It is therefore important to understand its contribution to the national and global NOx budget. Data from the South African Lightning Detection Network were used to approximate the influence of lightning on the NOx load over the country, and to develop a gridded data set of lightning-produced NOx (LNOx) emissions for the period 2008 2015. The Network monitors cloud-toground lightning strikes; and theoretically has a detection efficiency of 90% and a location accuracy of 0.5 km. An emission factor of 11.5 kg NO2/flash was employed to calculate the LNOx budget of ~270 kt NO2/year. The calculated LNOx was 14% of the total NOx emission estimates published in the EDGAR v4.2 data set for the year 2008. The LNOx emission inventory will improve model performance and prediction, and enhance the understanding of the contribution of lightning to ambient NO2.

NoneSocio-hydrology research is concerned with the understanding of how humanity interacts with water resources. The purpose of this study was to assess the disparity between global and African trends as well as developments in the research domain of socio-hydrology. From the viewpoint of a multitude of research themes, multi-author collaborations between African and international researchers and the number of publications produced globally, the results reveal that the field of socio-hydrology is still underdeveloped and yet nascent. At a global level, the USA, China, and the Netherlands have the highest number of scientific publications, while in Africa, South Africa dominates, although these scientific publications are significantly much lower than the global output. The output of scientific publications on socio-hydrology research from Africa increased from 2016, with significant output reached in 2019. Water management and supply, hydrological modelling, flood monitoring as well as policies and decision-making, are some of the dominant themes found through keywords co-occurrence analysis. These main keywords may be considered as the foci of research in socio-hydrology. Although socio-hydrology research is still in the early stages of development in Africa, the cluster and emerging themes analysis provide opportunities for research in Africa that will underpin new frontiers of the research agenda encompassing topics such as the (1) impacts of climate change on socio-hydrology; (2) influence of socio-hydrology on water resources such as surface water and groundwater; (3) benefits of socio-hydrological models on river basins and (4) role of socio-hydrology in economic sectors such as agriculture. Overall, this study points to a need to advance socio-hydrology research in Africa in a bid to address pressing water crises that affect sustainable development as well as to understand the feedback mechanisms and linkages between water resources and different sectors of society. Significance:•The field of socio-hydrology is still under-researched in Africa.• Limited research could be attributed to a lack of expertise, resources and data limitations.• Socio-hydrology research is likely to be strengthened through collaborations between Africa and other developed countries.• Existing gaps present opportunities to advance socio-hydrology research in Africa.