California droughts caused mainly by changes in wind, not moisture

California droughts caused mainly by changes in wind, not moisture
California as viewed from the International Space Station. Credit: NASA, Stuart Rankin

Droughts in California are mainly controlled by wind, not by the amount of evaporated moisture in the air, new research has found.

The findings were published in Geophysical Research Letters, a journal of the American Geophysical Union, on June 30. The research increases the understanding of how the water cycle is related to and could eventually help in predicting and floods, said lead author Jiangfeng Wei, a research scientist at The University of Texas at Austin's Jackson School of Geosciences.

"Ocean evaporation provides moisture for California precipitation but is not the reason for droughts there, although the ocean evaporation is slightly lower during droughts," Wei said.

The researchers analyzed 30-year data sets that recorded precipitation, ocean evaporation, surface wind speed and atmospheric pressure on and near the west coast of the United States. These are all factors that influence the water cycle in California. One of the difficulties of studying the , Wei said, is that the water sources for precipitation cannot be directly observed, so the team also used a mathematical moisture-tracking method and high-resolution model simulations.

Their analysis showed that although moisture evaporated from the Pacific Ocean is the major source for California precipitation, the amount of water evaporated did not strongly influence precipitation in California, except in the cases of very heavy flooding. That's because the amount of water evaporated from this ocean region does not change much year by year, researchers found, and did not cause rain to occur more or less often.

"Ocean evaporation has little direct influence on California because of its relatively weak variability," Wei said.

Instead, the researchers found that disturbances in atmospheric circulation, the large-scale movement of air, have the most effect on drought because they can affect factors that will cause it to rain more or less.

The study co-authors are Qinjian Jin, a postdoctoral researcher at the Massachusetts Institute of Technology who earned his Ph.D. at the Jackson School; Zong-Liang Yang, a professor in the Jackson School's Department of Geological Sciences; and Paul Dirmeyer, a professor at George Mason University.

Most of California has been in a severe drought since 2011, although a strong El Niño in the winter of 2015 helped diminish the drought. The current drought is caused by a high-pressure system that disturbs the atmospheric circulation. The development of the high-pressure system is related to a sea surface temperature pattern in the Pacific Ocean, according to research cited by the study.

"Although this is a very rare event, the probability of this kind of high-pressure system is likely increasing with global warming," the authors said.

Yang said that the research could aid in the prediction of droughts and floods by improving scientific understanding of the intricate factors that influence rainfall the most.

"The topic is extremely timely as current and future climate change would mean more changes in extreme events such as droughts and floods," Yang said. "Understanding this asymmetric contribution of ocean evaporation to drought and flooding in California will ultimately help us make better predictions."


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NASA maps El Nino's shift on US precipitation

More information: Jiangfeng Wei et al, Role of ocean evaporation in California droughts and floods, Geophysical Research Letters (2016). DOI: 10.1002/2016GL069386
Journal information: Geophysical Research Letters

Citation: California droughts caused mainly by changes in wind, not moisture (2016, July 5) retrieved 20 May 2019 from https://phys.org/news/2016-07-california-droughts-moisture.html
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Jul 05, 2016
o monkeygoracle... where are youuuu, i am waiting for youuuu.....

Jul 06, 2016
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Jul 06, 2016
The "droughts" are caused mostly by Marxist one-party rule in California. The agricultural industry has been decimated by the environuts' concern for the snail darter over people, diverting precious water away from the once luscious Central Valley, which is now becoming another dustbowl.

The political corruption and greed in Sacramento in the '80s, when CA had a much lower population, prevented addressing the water resources problem back then. Now it's way too late - and there's a useless choo-choo way over budget that must be completed first.

Smothering regulations and taxes are forcing businesses to leave. Their answer? More regulations and higher taxes; yeah, that'll fix it.

Jul 06, 2016
"Throughout history, poverty is the normal condition of man. Advances which permit this norm to be exceeded — here and there, now and then — are the work of an extremely small minority, frequently despised, often condemned, and almost always opposed by all right-thinking people. Whenever this tiny minority is kept from creating, or (as sometimes happens) is driven out of a society, the people then slip back into abject poverty.

This is known as "bad luck."

― Robert A. Heinlein

California, and, after 8 years of an anti-American president, the United States, are now in the beginning of an extended run of "bad luck."

Jul 06, 2016
o monkeygoracle... where are youuuu, i am waiting for youuuu.....

The science oozing from your posts is cutting edge stuff....what are you, an 11 year old?

Aaaa heeeere you are, i was waiting for youuuu, Science oozing ? it sure is, highlighting those who contribute sprightly to the forum is my specialty, but so is highlighting those doing monkey business, ....guess in which category youuuuu are classified in.... :D now.... let's have some fun, starting with pronouncing science, before you can begin to understand science, go look in the mirror and practice saying it ! Eeeveryday now..... you can do it.. ;)

Jul 06, 2016
What are you, another antisciencemarmoset puppet? If not I guess you're such an idiot that you identify with other idiots. Either way, you're a pitiful puddle of sick.


One in about 30 odd puppets, posting dumbfounded comments is his life, how sad it must be, posting 24/7 without eating or sleeping. But hey... i'm having so much fun... :D

Jul 06, 2016
This comment has been removed by a moderator.

Jul 07, 2016
What are you, another antisciencemarmoset puppet? If not I guess you're such an idiot that you identify with other idiots. Either way, you're a pitiful puddle of sick.


Well disney godfather, I only post here as myself under my own name. Unlike the juvenile 3 word mishmash handles that clearly all originate from the den of stupidity...AKA home of the whopper,

Aaaa heeeere you are, i was waiting for youuuu, Science oozing ? it sure is,


Really? Please point it out, all I see is trash talk and a strikingly low IQ for someone operating a computer....


Aaaahh....Naaa i got pletnty of friends here they are all respectable scientists, on th other han, all you see is the usual for you, you an your socks are drowned in science on this site but somehow cant seem to either see it or understand it, one thing i've realise is that you an your socks like to compete for bananas.. monkey wants another banana :D

Jul 07, 2016
Go back to your jar of Nutella, you nasty troll. Maybe laced with Lithium? It'll help that uncontrollable laughter. It'll make you less of a threat to others, too.


Yeah monkey gorailicle's got a row of 30 odd socks that hasn't been washed for years incluing bschotty, the stench itself might be worse than any kind of warming even if i must say so myself.

Jul 07, 2016
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Jul 07, 2016
I love it when a monkey tries to preach to the science community, it's like a hamster running his wheel, getting nowhere..... in this case antigoricale's sock biscuitt swinging those tree branches in circles...ooopp, remember.... gotta stop for that banana or you'll fall down.... ;)

Jul 07, 2016
The only solution is to create more debt and pay interest to ziofascists so they can fund more "studies"
The "droughts" are caused mostly by Marxist one-party rule in California. The agricultural industry has been decimated by the environuts' concern for the snail darter over people, diverting precious water away from the once luscious Central Valley, which is now becoming another dustbowl.
Yes I read about some county where come bug was declared endangered by some city bureaucrat, who prior had purchased a large tract of land. The ban on development made her land tract increase 20 times in price

Jul 07, 2016
Yes I read about some county where come bug was declared endangered by some city bureaucrat, who prior had purchased a large tract of land. The ban on development made her land tract increase 20 times in price
And she was Jewish, right?

You're never gonna live that down. You know that, right? The funniest part was when you started hinting I was a Jew. It was absolutely classical paranoid ideation. Thanks for participating in the sociology experiment.

Jul 09, 2016
This comment has been removed by a moderator.

Jul 10, 2016
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