According to AGU Publications, a recent study conducted by scientists at the University of Washington revealed that when the moon is high up in the sky, it creates bulges in the atmosphere that change the amount of rainfall on Earth. When the moon is overhead or underfoot (meaning high overhead on the other side of the Earth), an area will experience high pressure and less rainfall.
“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,” stated the University of Washington scientists in a press release.
Tsubasa Kohyama, an atmospheric sciences doctorate student, observed a slight difference in the Earth’s air pressure while studying atmospheric waves, which prompted Kohyama and atmospheric sciences professor John Wallace to investigate the occurrence. The recent UW study used a global grid of data to confirm that air pressure on the Earth’s surface varies with the moon phases, which strengthened Wallace and Kohyama’s inclination.
When the moon is overhead, its gravitational pull causes Earth’s atmosphere to bulge towards it. This pull increases the weight or pressure of the atmosphere on this side. The Moon’s force is trying to suck the Earth’s atmosphere closer to it, while affecting the amount of air inside it at the same time. According to the study, higher atmospheric air pressure increases the temperature of air particle on earth, which increases the amount of moisture that those particles can contain. This moisture capacity affects the amount of rain and lower humidity is less likely to result in precipitation according to Kohyama.
“No one should carry an umbrella just because the moon is rising,” Kohyama says.
Kohyama and Wallace studied data from NASA and the Tropical Rainfall Measuring Mission satellite of the Japan Aerospace Exploration Agency, which revealed that rain is lighter when the Moon is high. However, the change is only about one percent of total rainfall variation. This study allows scientists to form better climate models based on the Moon’s position and gives the general public insight on the Moon’s true affects on rainfall.