Understanding the variability of heatwave characteristics in southern Africa

Abstract

Southern Africa is among the regions facing the impacts of weather-related extremes (e.g., droughts, floods and heatwaves). In this study we investigate the spatial and temporal variability of heatwave characteristics (duration, number, frequency, amplitude, and cumulative magnitude) over the southern African region during the extended austral summer (November to March) for the period of 1981/82–2017/2018. Heatwaves were identified using three different approaches, namely, the 90th percentile of minimum daily temperature (CTN90pct), the 90th percentile of daily maximum temperature (CTX90pct) and the Excess Heat Factor (EHF), which is a relatively new method. We performed a Principal Component Analysis (PCA) on each of the five heatwaves characteristics to extract the dominant modes. We inspected the role of large-scale climate drivers on the different modes of heatwave characteristics. The results reveal that all the three heatwave definitions capture the key spatial patterns of heatwave characteristics over the southern African region. However, compared to other two definitions, the minimum temperature-based definition recorded fewer heatwave events over the bulk southern Africa. The El Niño Southern Oscillation (ENSO) was identified as one of the key climate drivers associated with different heatwave characteristics over the southern African region. The findings from this study expand our understanding of heatwaves variability over southern Africa. Moreover, results from this study are relevant to the heatwave forecasting over southern Africa.