Abstract
Global warming has increased the frequency of extreme weather events, including heatwaves, over recent decades. Heat early warning systems are being set up in many regions as a tool to mitigate their effects. Such systems are not yet implemented in the West African Sahel, partly because of insufficient knowledge on the skill of models to predict them. The present study addresses this gap by examining the skill of the ECMWF ENS extended-range forecasting system (ENS-ext) to predict Sahelian heatwaves out to subseasonal lead-times. It also assesses the importance of tropical modes of variability, which were previously identified as important large-scale drivers of heatwave occurrence in the Sahel. The results show that ENS-ext is able to predict Sahelian heatwaves with significant skill out to lead-week 2–3. With increasing lead-time, heatwaves are more predictable at nighttime than at daytime. Likewise, the pre-monsoon season heatwaves have a longer predictability than those occurring in late winter. The model is also able to relatively well simulate the observed relationship between heatwave occurrence and tropical mode activity. Furthermore, the prediction skill is better during the active phases of the modes, suggesting that they are good sources of heatwave predictability. Therefore, improving the representation of tropical modes in models will positively impact heatwave prediction at the subseasonal scale in the Sahel, and gain more time and precision for anticipatory actions.
Highlights
The recent developments in climate change are marked by an increased occurrence of extreme weather and climate events, including heatwaves (Stott 2016)
Climate projections anticipate an increase of the magnitude, spatial extent and frequency of extreme heat events (Russo et al 2016; Dosio 2017; Sylla et al 2018) that could only aggravate the thermal risk in the region
The AMJ season has a longer lead-time predictability than the FM season, likewise nighttime heatwaves are better predicted at longer lead-times than their daytime counterparts
Summary
The recent developments in climate change are marked by an increased occurrence of extreme weather and climate events, including heatwaves (Stott 2016). There has been an upward trend of heatwaves both at the global and regional levels (Perkins-Kirkpatrick and Lewis 2020), with future projections warning of even more severe thermal discomfort (Xu et al 2020; Raymond et al 2020) for the human community. Over the recent decades and in agreement with the global trend, they have been more frequent, more intense (especially at night) and longer lasting (Fontaine et al 2013; Ringard et al 2016; Moron et al 2016; Oueslati et al 2017; Barbier et al 2018). Climate projections anticipate an increase of the magnitude, spatial extent and frequency of extreme heat events (Russo et al 2016; Dosio 2017; Sylla et al 2018) that could only aggravate the thermal risk in the region
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