Researchers at the Swiss Federal Institute of Technology in Zurich (ETH) have come up with a new explanation for the heatwave that has taken hold in Europe.
Two forces appear to be at work. The first is a large body of hot or high pressure air in the troposphere, at 5,000 to 10,000 metres above sea level, that blocks westerly Atlantic air currents and low pressure systems. These high pressure systems can be as wide as 2,000 kilometres.
The second is known as latent heat. When you sweat the evaporating water cools your body. Heini Wernli’s team at ETH discovered a meteorological phenomenon that appears to do this in reverse. As large bodies of air rise, instead of the water evaporating generating a cooling effect, it condenses creating heat. The heat generated causes the air to rise further and helps to create these stable high pressure systems in the troposphere that cause blockages.
The researchers analysed 21 years of data from balloons, aircraft, satellites and the ground, which showed higher levels of latent heat generation preceding high pressure blockages. In the future this know how could help to predict heatwaves.
Read full 24 Heures article here (in French)