An area sees higher air pressure — and therefore less rain — when the moon is overhead or underfoot (meaning high overhead on the other side of the Earth), the scientists say. This is how it works, according to the press release:
"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."
We're talking about a very small change here — "only about 1 percent of the total rainfall variation," the university notes.
"No one should carry an umbrella just because the moon is rising," Kohyama says.
While we won't be able to perceive the moon's impact on rainfall, the data could be helpful for researchers making climate models, "to check if their physics is good enough to reproduce how the pull of the moon eventually leads to less rain," the press release states.
The moon's impact on ocean tides is well known. In a previous paper, the two scientists connected air-pressure changes to the position of the moon.