European mega-heatwaves linked to drought

August 21, 2019

Heatwaves in Europe have become increasingly frequent and intense in recent years. This summer, Western Europe has already been hit by two severe heatwaves. Researchers from Ghent University and Wageningen University & Research have found a common ingredient of such European mega-heatwaves: drought conditions in the regions the wind blows from.

Relying on satellite observations and modelling techniques, the researchers quantify the degree to which air masses warm up in drought locations to then contribute to the escalation of temperatures in the regions downwind. This researcher, funded by the European Research Counsel (ERC), implies a sequence of natural disasters, in which upwind droughts help unleash downwind heatwaves.

Sudden changes in wind direction, transporting heat from these arid locations, can lead to abrupt temperature increases. These ‘heat torrents’ fuelled by upwind droughts were responsible for about 30% of the heat anomaly during the 2003 and 2010 European mega-heatwaves.

Air from North Africa intruding into European mainland

According to lead author Dominik Schumacher (Ghent University), the situation during the heatwaves experienced this summer has been similar. “Normally hot air cools down above oceans and vegetation. But travelling over drought-struck France and Spain, hot and dry air from North Africa could intrude far into the European mainland”. This situation would be analogous to the heatwaves experienced in 2003 and 2010, when the air did not come from the Sahara but from regions in Eurasia that were experiencing extreme droughts.

Better prepared for heatwaves

This study, funded by the European Research Council (ERC), links upwind droughts to downwind heatwaves for the first time. The results art particularly relevant in the face of climate change. “Our atmosphere is slowly but steadily heating up due to climate change,” Schumacher adds. “Drought conditions are projected to aggravate, which could trigger even more extreme mega-heatwaves in the future”.

Developing adaptation strategies is complex according to co-author Jordi Vilà-Guerau de Arellano (Wageningen University & Research). “Weather warm air masses travelling above very dry soil conditions become even warmer and they further enhance the local heatwaves. This additional heat is arriving suddenly and intensely, like a torrent. This unpredictability and the interactions between local and continental conditions, needs to be account for in heatwave adaptation strategy."