Scientists break down 'eclipse wind' after 300 years of mystery

For a long time, scientists have noticed that the weather gets chillier during a solar eclipse, but have been completely baffled as to why that may be. Now, researchers finally believe they may have pinned down the cause for this eerie occurrence.

Meteorologists at the University of Reading, led by Dr Luke Barnard, were able to study this phenomenon by crowdsourcing data from 4,500 citizen scientists around the UK, in the National Eclipse Weather Experiment during the partial eclipse of 20 March 2015. Meanwhile, Professor Giles Harrison and Professor Suzanne Gray analysed data from the UK Meteorological Department, checking surface weather stations and roadside sensors for changes in temperature. 

The scientists found that the changes in wind pattern were caused by variations to the 'boundary layer', the layer of air that separates high-level winds from those below. This ‘eclipse wind’ is a change in wind direction and intensity that occurs when the moon temporarily blocks out the sun. As the sun is covered by the moon, the ground temperature rapidly drops, just as it does at sunset. When this happens, hot air stops rising from the ground and both the speed and direction of the wind changes.

Professor Giles said, "There have been lots of theories about the eclipse wind over the years, but we think this is the most compelling explanation yet… Our discovery was made possible thanks to data from the world's largest ever eclipse weather experiment combined with Met Office forecast data and measurement network observations. You can read more about the study here.