Moon’s tidal forces affect amount of rainfall on Earth
When the moon is high in the sky, it creates bulges in the planet’s atmosphere that creates imperceptible changes in the amount of rain that falls below.
New University of Washington research to be published in Geophysical Research Letters shows that the lunar forces affect the amount of rain – though very slightly.
“As far as I know, this is the first study to convincingly connect the tidal force of the moon with rainfall,” said corresponding author Tsubasa Kohyama, a UW doctoral student in atmospheric sciences.
Kohyama was studying atmospheric waves when he noticed a slight oscillation in the air pressure. He and co-author John (Michael) Wallace, a UW professor of atmospheric sciences, spent two years tracking down the phenomenon.
Satellite data over the tropics, between 10 degrees S and 10 degrees N, shows a slight dip in rainfall when the moon is directly overhead or underfoot. The top panel shows the air pressure, the middle shows the rate of change in air pressure, and the bottom shows the rainfall difference from the average. The change is 0.78 micrometers, or less than one ten thousandth of an inch, per hour. Image: University of Washington
Air pressure changes linked to the position of the moon was 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 position of the moon.
“When the moon is overhead or underfoot, the air pressure is higher,” Kohyama said.
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.”
Kohyama and Wallace used 15 years of data collected by NASA and the Japan Aerospace Exploration Agency’s Tropical Rainfall Measuring Mission satellite from 1998 to 2012 to show that the rain is indeed slightly lighter when the moon is high. The change is only about 1 percent of the total rainfall variation, though, so not enough to affect other aspects of the weather or for people to notice the difference.
“No one should carry an umbrella just because the moon is rising,” Kohyama said.
Instead, this effect could be used to test climate models, he said, to check if their physics is good enough to reproduce how the pull of the moon eventually leads to less rain.
Wallace plans to continue exploring the topic to see whether certain categories of rain, like heavy downpours, are more susceptible to the position of the moon, and whether the frequency of rainstorms shows any lunar connection.
The research was funded by the National Science Foundation, the Takenaka Ikueikai Scholarship Society, and the Iizuka Takeshi Scholarship Foundation.
See more here: washington.edu
Header image: Medium
Please Donate Below To Support Our Ongoing Work To Defend The Scientific Method
PRINCIPIA SCIENTIFIC INTERNATIONAL, legally registered in the UK as a company 
incorporated for charitable purposes. Head Office: 27 Old Gloucester Street, London WC1N 3AX.
Trackback from your site.
Jerry Krause
| #
Hi PSI Readers,
I was considering retiring from making comments here because my comments generate so few other comments from you. Even those which I consider to be extreme fundamental unimportance like common observations which absolutely prove the greenhouse theory of atmospheric carbon dioxide and similar gas to be absolute wrong. I am waiting to read about a debate whether the EARTH STANDSTILLS as if the Galileo’s telescopic observations did not absolutely prove that the idea that Earth did STAND STILL was absolutely wrong.
Alan, I have tried to find your comment again about temperature averages to a hundredth, or even, a thousandth of a degree relative the range of maximum-minimum temperatures measured during most any time and location. For now I read: “The change is 0.78 micrometers, or less than one ten thousandth of an inch, per hour.”
My comment is a question: Do you, a possible reader of this, believe that this student and his emeritus professor has ever tried to measure an hour’s precipitation to a thousandth of an inch???
And another question: Does everybody, but me, live in a fantasy world where ANYTHING IF POSSIBLE???
Have a good day, Jerry
Reply
Jerry Krause
| #
Hi again,
And a truth is that I often do not try to proofread before I submit because I have found that I never catch all my mistakes when I try to proofread.
But I trust that there of those of you who recognize my mistakes know, from the context, what I intended to write (type).
Again, have a good day, Jerry
Reply
Jerry Krause
| #
Hi again,
And a truth is that I often do not try to proofread before I submit because I have found that I never catch all my mistakes when I try to proofread.
But I trust that there of those of you who recognize my mistakes know, from the context, what I intended to write (type).
Again, have a good day, Jerry
Reply
MattH
| #
Which begs the question. If you take the same lack of care and precision with your experiments, how many laboratories have you blown to smithereens Jerry.
Fishermen in this part of the world have an observation that if the weather is rough on a full moon the whole following month will have relatively rough weather up until the next full moon.
In the recent article on “Maori science?” suggesting the moon at 18.6 year minor standstill correlates with El Nino events I suggested Ken Ring has a theory about correlation between the moon and earthquakes.
What I did not elucidate further is that Mr. Ring’s theory is that full moons in lunar perigee have an influence on major earthquakes. This is a theory often refuted but supported by a small number of scientists.
Mr. Ring’s weather map predictions are absolute garbage if used to predict sea state conditions (swell waves wind) but some farmers give credence to rain predictions based on lunar predictions.
OK then.
Reply
Jerry Krause
| #
Hi MattH,
You just wrote:and asked: “Which begs the question. If you take the same lack of care and precision with your experiments, how many laboratories have you blown to smithereens Jerry.”
First, I ask you: Should I really point out that you should have ended your question with a question mark instead of the period? My answer is NO! Because your error doesn’t change the intent of the words of your question.
I seem to remember that I have written here that as a good EXPERIMENTAL SCIENTIST that I, as an youth, spent hours weighing (massing) small vials to a reproducible few micrograms. With the result that my data did not look like a shotgun pellet pattern of maybe 24 pellets (hence 48 reproducible massing because the vials needed to be massed before and after. Whereas a post-doc could do this massing in 30 minutes and her experimental data did look much more like a shotgun pellet pattern when graphed while my data, when graphed, looked like a nearly smooth continuous curve even when straight lines were drawn from one data point to the next.
So, the answer to your first question is: NONE!!!
Matt you also just wrote: “This is a theory often refuted but supported by a small number of scientists.” The only thing which can support a SCIENTIFIC THEORY is OBSERVED (MEASURED IN SOME CASES) DATA. And any SCIENTIFIC THEORY should initially be an attempt to explain some reproducible data or an unconsidered possibility which might need to be considered (Einstein)
Historical cases in point: the sun rose and set daily. In this case there were two, somewhat obvious. explanations. Another early controversy was the question: Is matter endlessly divisible or is it particle like where the ultimate particle cannot be easily divided?
Thank you for your comments. For they provide context for my comments.
Have a good day, Jerry
Reply
MattH
| #
Hi Jerry.
Good spotting on the question mark. When I was involved in small time politics I came up with the saying, “hypocrisy is a beautiful thing”. I am still trying to dig the log out of my eye.
Have a great day Jerry. It is a perfect clear sky summer morning here. No wind yet.
Matt.
Reply
Jerry Krause
| #
Hi MattH,
Relative to: “No wind yet.” Take a look at a very ABNORMAL ATMOSPHERE over Salem that extends nearly to the Rockies. (http://weather.uwyo.edu/cgi-bin/sounding region=naconf&TYPE=TEXT%3ALIST&YEAR=2022&MONTH=01&FROM=2912&TO=2912&STNM=72694&ICE=1)
This is a really huge volume of atmosphere complete with a very significant air temperature inversion at it base. Someone needs to explain the cause of this abnormal atmosphere. Will wait to see if anyone else even notices it. For first it needs to be noticed before it can be explained.
Have a good day, Jerry
Reply
Jerry Krause
| #
This is a test.
(http://weather.uwyo.edu/cgibin/soundingregion=naconf&TYPE=TEXT%3ALIST&YEAR=2022&MONTH=01&FROM=2912&TO=2912&STNM=72694&ICE=1)
For the previous link was merely copied and pasted and what you see didn’t work. So I have tried a bit of editing and I, at this point, have no idea that this will work.
Reply