When the moon blocks the sun's rays during a solar eclipse, onlookers often feel a sudden shift in the wind direction. The phenomenon is called an "eclipse wind," and for decades, scientists have struggled to explain why it happens.

Thanks to the National Eclipse Weather Experiment, astronomers and meteorologists are no longer in the dark.

To solve the mystery, a team of researchers from the University of Reading in England recruited several thousand citizen scientists to gather meteorological readings during last year's solar eclipse. The measurements showed the air at ground level quickly cools as the sun disappears behind the moon. Low-level winds also slacken.

Additional data from the Met Office and its roadside weather stations suggested the shift in wind direction is triggered by perturbations in the "boundary layer," the buffer of air dividing high-level winds from ground-level breezes.

"As the sun disappears behind the moon the ground suddenly cools, just like at sunset," Giles Harrison, a meteorology professor at Reading, explained in a news release. "This means warm air stops rising from the ground, causing a drop in wind speed and a shift in its direction, as the slowing of the air by the Earth's surface changes."

Harrison and his colleagues detailed their latest findings in two separate papers, both published in the journal Philosophical Transactions of the Royal Society A.

"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," Harrison added. "We thank the thousands of fellow scientists around the country whose measurements contributed to this research."