Fine-resolution analysis of the spatiotemporal characteristics of heatwaves in the Maloti-Drakensberg region, southern Africa: 1979–2021

Abstract

Consistent with global patterns, heatwaves have increased in frequency, duration and intensity across southern Africa; under enhanced global warming this is projected to worsen. Heatwaves have many adverse impacts, but in biologically unique mountainous regions, like the Maloti-Drakensberg region, impacts on ecological processes and hydrological cycles are particularly dire given their highly sensitive nature. Despite this, extreme temperature changes and interannual variability patterns remain understudied in mountainous regions, owing largely to remoteness and inaccessibility. This is especially true for the Maloti-Drakensberg region. Hence, using heatwave indices developed by the World Meteorological Organization (WMO) Expert Team on Sector-Specific Climate Indices (ET-SCI), we explored spatiotemporal patterns for the seasonal average number, length and magnitude of summer (November-March) heatwaves for 1979/80–2020/21 using the AgERA5 reanalysis. Although higher elevation regions typically experienced more frequent, longer-lasting heatwave events with higher interannual variability levels, on average the Maloti-Drakensberg region experienced 1.4 heatwave events, lasting for 6.5 days with a magnitude of 3.5°C2. Interannually, the El Niño-Southern Oscillation influenced variability of heatwave characteristics, with positive (negative) heatwave number and length anomalies predominantly detected during El Niño (La Niña) phases, while for heatwave magnitudes no clear pattern was evident. These heatwave aspects were predominantly characterised by increasing trends, however, few regions exhibited statistically significant trends. Overall, trends averaged 0.003 events/year, 0.03 days/year and 0.02°C2/year for the mean number, length and magnitude of heatwaves, respectively. These results highlight that the Drakensberg-Maloti region is vulnerable to an increasing frequency, duration and magnitude of heatwaves, however, implications thereof require further study.