Future Changes in Winter-Time Extratropical Cyclones over South Africa
from CORDEX-CORE Simulations
Abstract
Extratropical cyclones (ETCs) significantly impact mid-latitude weather
patterns and are crucial for understanding the societal implications of
regional climate variability, climate change, and associated extreme
weather. In this study, we examine the projected future changes in
winter-time ETCs over South Africa (SA) using simulations from
CORDEX-CORE Africa. We utilized three regional climate models (RCMs),
each driven by three different global climate models (GCMs) that
simulate both the current climate and a future climate experiencing
strong human-induced warming. From these, we assess changes in ETC
frequency, track density, intensity, storm severity, and associated
rainfall. The results indicate a significant reduction in the aggregate
ETC frequency and track density, although track density is projected to
increase prominently along the western coastal regions. Intensity
projections show mixed trends, with an aggregate decrease in peak
relative vorticity and an increase in minimum mean sea level pressure,
suggesting weaker future cyclones. Examining the Meteorological Storm
Severity Index (METSSI) reveals notable regional variations in future
storm severity. Average rainfall associated with ETCs is projected to
decrease across SA, especially around Cape Town, highlighting a
potential shift in the spatial distribution of rainfall with substantial
consequences for water supply. We further investigated extreme ETCs
(EETCs) and found that the trends for EETCs are generally similar to
those for ETCs, with a notable decrease in frequency but regional
variations in storm severity. These findings underscore the importance
of developing targeted adaptation strategies to address the projected
impacts of future ETCs on SA’s climate and communities.