Fires Blast California. And it Will Get Worse

December 7, 2017

Apocalyptic images from fires around LA.

Time:

Southern California has felt yellow wind, orange wind, and red wind. But never purple wind. Until now.

The color-coded system showing the expected strength of the winds driving the region’s fierce wildfires has reached uncharted territory, pushing past red, which means “high” into the color that means “extreme.”

“The forecast for tomorrow is purple,” said Ken Pimlott, director at the California Department of Forestry and Fire Protection. “We’ve never used purple before.”

Scientific American:

Loss of ice cover in the Arctic could spur more droughts in California, according to a new study by federal researchers.

The study, published today in Nature Communications, finds that sea-ice loss in the Arctic could trigger atmospheric effects that drive precipitation away from California. The research was led by atmospheric scientists at the Lawrence Livermore National Laboratory.

It’s the same kind of effect that contributed to state’s historic dry period that ended last year. The five-year drought was exacerbated by an atmospheric pressure system in the North Pacific Ocean that researchers dubbed the “ridiculously resilient ridge,” which pushed storms farther north and deprived the Southwest of precipitation.

“[S]ea-ice loss of the magnitude expected in the next decades could substantially impact California’s precipitation, thus highlighting another mechanism by which human-caused climate change could exacerbate future California droughts,” the study says.

The study stops short of attributing California’s latest drought to changes in Arctic sea ice, partly because there are other phenomena that play a role, like warm sea surface temperatures and changes to the Pacific Decadal Oscillation, an atmospheric climate pattern that typically shifts every 20 to 30 years.

The recent drought is also outside the study’s scope because the researchers focused on potentially larger losses in sea ice than have occurred to date. The authors predict that over the next 20 years, California could see a 10 to 15 percent decrease in rainfall on average.

“The recent California drought appears to be a good illustration of what the sea-ice drive precipitation could look like,” lead researcher Ivana Cvijanovic said in a release. “While more research should be done, we should be aware that an increasing number of studies, including this one, suggest that the loss of Arctic sea ice cover is not only a problem for remote Arctic communities, but could affect millions of people worldwide.”

Conversely, sea-ice loss in the Antarctic would be expected to increase California’s precipitation, according to the study’s modeling. The North Pacific atmospheric ridge would be replaced by a trough, encouraging tropical storms to develop over the state.

Previous studies have hypothesized that the North Pacific atmospheric ridge is caused by increased ocean surface temperatures and movement of heat in the tropical Pacific. The new study elaborates on that understanding by describing the link between Arctic sea-ice loss and tropical convection.

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Nature Communications:

From 2012 to 2016, California experienced one of the worst droughts since the start of observational records. As in previous dry periods, precipitation-inducing winter storms were steered away from California by a persistent atmospheric ridging system in the North Pacific. Here we identify a new link between Arctic sea-ice loss and the North Pacific geopotential ridge development. In a two-step teleconnection, sea-ice changes lead to reorganization of tropical convection that in turn triggers an anticyclonic response over the North Pacific, resulting in significant drying over California. These findings suggest that the ability of climate models to accurately estimate future precipitation changes over California is also linked to the fidelity with which future sea-ice changes are simulated. We conclude that sea-ice loss of the magnitude expected in the next decades could substantially impact California’s precipitation, thus highlighting another mechanism by which human-caused climate change could exacerbate future California droughts.

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2 Responses to “Fires Blast California. And it Will Get Worse”

  1. andrewfez Says:

    That junk is nasty. Somehow the wind blew ashes up through my skylight and coated my upstairs. Just walking around outside, I was getting floating particulates in my eyes left and right. I keep my upstairs window open constantly, and my place stank of burnt chaparral for a day or so. Probably filled up the ER’s with asthma patients. The fire (one of the fires) killed a bunch of horses 10 miles north of here – so sad!

    We already know from history what happens to CA when the heat is turned up 1C in the N hemisphere. During the MWP this place suffered multi-decade mega droughts, one after the other. I have conservative friends thinking all the rain we had in 2016 was the end of the drought…


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