Major heat waves driven by feedback cycle from drying soil

Nature : In Europe in 2003 and Russia in 2010, major heat waves were responsible for record-breaking high temperatures and large numbers of deaths. Diego Miralles of Ghent University in Belgium and his colleagues examined a wide range of data and believe they’ve found one of the significant contributors. Temperature and soil moisture measurements from before and during the heat waves revealed that soil drying was creating a feedback cycle that helped exacerbate the system. Heat waves occur when high-pressure systems become stationary and trap warm air near the ground. In the case of the two major heat waves, the systems formed in areas with low soil moisture. The system dried the ground even further, which fed more heat from the ground into the air. The extra heat couldn’t be dissipated by overnight cooling, creating a cycle of soil drying and air heating that repeated daily. The data doesn’t explain why the high-pressure systems remained stationary for so long and doesn’t address whether climate change will make such events more common or more intense.