Washington DC: A team of scientists has shown that there is a degree of truth in the ancient folklore "rain follows the full and new phases of the moon."
The University of Washington research shows that the lunar forces affect the amount of rain - though very slightly.
Air pressure changes linked to the phases of the moon were first detected in 1847 and temperature in 1932 in ground-based observations. An earlier paper by the UW researchers used a global grid of data to confirm that air pressure on the surface definitely varies with the phases of the moon.
Corresponding author Tsubasa Kohyama said that when the moon is overhead or underfoot, the air pressure is higher.
Their new paper is the first to show that the moon's gravitational tug also puts a slight damper on the rain.
When the moon is overhead, its gravity causes Earth's atmosphere to bulge toward it, so the pressure or weight of the atmosphere on that side of the planet goes up. Higher pressure increases the temperature of air parcels below. Since warmer air can hold more moisture, the same air parcels are now farther from their moisture capacity.
"It's like the container becomes larger at higher pressure," Kohyama said. The relative humidity affects rain, he said, because "lower humidity is less favorable for precipitation."
The study will be published in Geophysical Research Letters