After looking at fifteen years of climate data, scientists from the University of Washington (UW) found that the Moon may influence rainfall on Earth – less rainfalls take place when the Moon is directly overhead in the sky.
Tsubasa Kohyama, a doctoral student in atmospheric sciences at the University of Washington, hypothesised that there might be a connection between oscillating air pressure and atmospheric waves. He and John Wallace, a professor of Atmospheric Sciences at the University of Washington, and former director of the Joint Institute for the Study of the Atmosphere and Ocean (JISAO), began analysing over a decade’s worth of climate data to confirm his assumption.
The data collected by the National Aeronautics and Space Administration and the Japan Aerospace Exploration Agency’s Tropical Rainfall Measuring Mission (TRMM) over a period of fifteen years – from 1998 to 2012 – confirmed the fact that the moon is linked with Earth’s rainfall.
According to Kohyama, whenever the moon is overhead or underfoot, the air pressure is also higher, which allows for more moisture. In other words, Earth’s atmosphere protrudes toward the moon – when the moon is at its peak – due to gravitational pull, which then also increases the atmospheric pressure. “It’s like the container becomes larger at higher pressure,” Kohyama stated.
A previous study from 2014 – which was also conducted by Professor Wallace and Kohyama – found that during certain phases of the moon, the pressure on Earth’s surface increased. That took place especially when the moon was directly underfoot or overhead.
Kohyama and Professor Wallace said that this is the first study to conclusively connect rainfall on Earth with the tidal force of the moon.
However, the average person will not notice a difference in rainfall when the moon is overhead or underfoot, the researchers explained. The new findings are only important for scientists in the field, since the change in rainfall due to the moon is about one percent of the overall rainfall variation. No one should be carrying an umbrella just because the moon happens to be at its peak, Kohyama noted.
The new data could be eventually used by atmospheric scientists to test various climate models, according to Prof. Wallace.
The findings were published on Saturday (Jan. 30) in the Geophysical Research Letters.
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