It is well known that the moon’s gravity affects tides in the world’s oceans. Now scientists have found that the changing lunar phases also impact the amount of rainfall on our planet, albeit very slightly. Scientists at the University of Washington said the rain is slightly lighter when the moon is high. Findings of the study were published in the Geophysical Research Letters.
Rain is lighter when the moon is high in the sky
Tsubasa Kohyama, the lead author of the study and a doctoral student at the University of Washington, said when the moon is high in the sky, it causes bulges in the Earth’s atmosphere. It leads to imperceptible changes in the amount of rainfall. It is the first time that the lunar tidal forces have been convincingly connected with rainfall on Earth, said Kohyama.
Scientists were studying atmospheric waves when they noticed a slight oscillation in the air pressure. They spent over two years tracking down the phenomenon. Air pressure changes linked to the lunar phases were detected for the first time in 1847. A previous study published in 2014 used a global grid of data to confirm that air pressure on the Earth surface varies with the lunar phases.
The study is based on 15 years of data
The air pressure is higher when the moon is overhead or underfoot. When it is overhead, its gravity causes our planet’s atmosphere to bulge towards it. So, the weight or pressure of the atmosphere on that side of Earth goes up. Increased pressure leads to a higher temperature of air parcels below. Warmer air holds more moisture, so these air parcels are now farther from their moisture capacity.
Tsubasa Kohyama and his colleagues used 15 years of data collected by the Japan Aerospace Exploration Agency and NASA from 1998 to 2012 to show that the rainfall on Earth is lighter when the moon is high. However, it accounts for only 1% of the total rainfall variation, so it is difficult for people to notice the difference. Scientists said they would continue to explore the topic to find out whether the frequency of rainstorms has any lunar connection or whether heavy downpours are more susceptible to lunar phases.
