Abstract
This study is motivated to highlight the variability of recent drought hotspots in the region of southern Africa in terms of the seasonal and annual rainfall regimes and their possible spatial linkage with the 1950-2020 seasonal El Niño/Southern Oscillation (ENSO). Some evidence is found on possible links between the occurrence of drought hotspots in the region in terms of seasonal and mean annual runoff and warm ENSO events. This was revealed by the existence of a strong and nearly-strong positive linear correlation between Seasonal and annual rainfall depths and the warm seasonal ENSO indices explained by the southern oscillation index represented by the sea level pressure (SLP) anomalies data obtained from the National Oceanographic and Aeronautics Administration (NOAA). Considering the entire southern African region, 41% of the surface areas exhibit moderate (r > 0.25) and strong (r > 0.5) correlation coefficients in terms of the December to February quarter rainfall and ENSO indices. Above 50% confidence interval in the correlation between seasonal rainfall and ENSO during DJF quarters is found in 74% of the surface area of the region of southern Africa. The high confidence interval of the positive correlation coefficients is an indication that substantial variance of precipitation during ENSO years is accounted for by the warm ENSO events. The areas with pronounced lower rainfalls and droughts associated with ENSO activity in the region include larger and some pockets of various countries in southern Africa, including but not limited to Angola, Botswana, Lesotho, Namibia, Zambia, Zimbabwe, South Africa and Mozambique. The recent drought events of 2019/2020, and previously in 2015/16 in this region with wider regional impacts can be explained by the ENSO phenomena.
Highlights
El Niño/Southern Oscillation (ENSO) events dramatically alter oceanic conditions, climate and weather patterns across the globe and significant correlations between large-scale regional precipitation patterns and ENSO episodes have been identified for several specific regions around the world
This was revealed by the existence of a strong and nearly-strong positive linear correlation between Seasonal and annual rainfall depths and the warm seasonal ENSO indices explained by the southern oscillation index represented by the sea level pressure (SLP) anomalies data obtained from the National Oceanographic and Aeronautics Administration (NOAA)
50% confidence interval in the correlation between seasonal rainfall and ENSO during DJF quarters is found in 74% of the surface area of the region of southern Africa
Summary
ENSO events dramatically alter oceanic conditions, climate and weather patterns across the globe and significant correlations between large-scale regional precipitation patterns and ENSO episodes have been identified for several specific regions around the world On a seasonal time-scale, the ENSO phenomenon affects the atmospheric circulation outside the tropics [7] [8]. ENSO is an atmospheric phenomenon that has long been known to have a characteristic manifestation in Southern Africa whereby warm-phase episodes are associated with droughts while cold-phase episodes lead to wetter than normal conditions. The influence of ENSO events is profoundly felt outside the tropics as well including southern Africa as noted in recent literature on evolution of southern African summer precipitation as noted by Monerie et al [18] Hoell et al [19] [20]; on ENSO teleconnections e.g. Jury [2], Archer et al [21] Winsemius et al [22] Alemaw & Chaoka [23] and seasonal rainfall predictions as noted by Rautenbach [15] Landman & Klopper [14]
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