Climate change may lead to bigger atmospheric rivers

Climate change may lead to bigger atmospheric rivers
In early 2017, the Western United States experienced rain and flooding from a series of storms flowing to America on multiple streams of moist air, each individually known as an atmospheric river. Credit: NASA/JPL-Caltech

A new NASA-led study shows that climate change is likely to intensify extreme weather events known as atmospheric rivers across most of the globe by the end of this century, while slightly reducing their number.

The new study projects will be significantly longer and wider than the ones we observe today, leading to more frequent atmospheric river conditions in affected areas.

"The results project that in a scenario where greenhouse gas emissions continue at the current rate, there will be about 10 percent fewer atmospheric rivers globally by the end of the 21st century," said the study's lead author, Duane Waliser, of NASA's Jet Propulsion Laboratory in Pasadena, California. "However, because the findings project that the atmospheric rivers will be, on average, about 25 percent wider and longer, the global frequency of atmospheric river conditions—like heavy rain and strong winds—will actually increase by about 50 percent."

The results also show that the frequency of the most intense atmospheric river storms is projected to nearly double.

Atmospheric rivers are long, narrow jets of air that carry huge amounts of water vapor from the tropics to Earth's continents and polar regions. These "rivers in the sky" typically range from 250 to 375 miles (400 to 600 kilometers) wide and carry as much water—in the form of water vapor—as about 25 Mississippi Rivers. When an atmospheric river makes landfall, particularly against mountainous terrain (such as the Sierra Nevada and the Andes), it releases much of that water vapor in the form of rain or snow.

These storm systems are common—on average, there are about 11 present on Earth at any time. In many areas of the globe, they bring much-needed precipitation and are an important contribution to annual freshwater supplies. However, stronger atmospheric rivers—especially those that stall at landfall or that produce rain on top of snowpack—can cause disastrous flooding.

Atmospheric rivers show up on satellite imagery, including in data from a series of actual atmospheric river storms that drenched the U.S. West Coast and caused severe flooding in early 2017.

The Study

Climate change studies on atmospheric rivers to date have been mostly limited to two specific regions, the western United States and Europe. They have typically used different methodologies for identifying atmospheric rivers and different projection models—meaning results from one are not quantitatively comparable to another.

The team sought to provide a more streamlined and global approach to evaluating the effects of on atmospheric river storms.

The study relied on two resources—a set of commonly used global climate projections for the 21st century developed for the Intergovernmental Panel on Climate Change's latest assessment report, and a global atmospheric river detection algorithm that can be applied to climate model output. The algorithm, developed earlier by members of the study team, identifies atmospheric river events from every day of the model simulations, quantifying their length, width and how much water vapor they transport.

The team applied the atmospheric river detection algorithm to both actual observations and model simulations for the late 20th century. Comparing the data showed that the models produced a relatively realistic representation of atmospheric rivers for the late 20th century climate.

They then applied the algorithm to model projections of climate in the late 21st century. In doing this, they were able to compare the frequency and characteristics of atmospheric rivers for the current climate with the projections for future climate.

The team also tested the algorithm with a different climate model scenario that assumed more conservative increases in the rate of greenhouse gas emissions. They found similar, though less drastic changes. Together, the consideration of the two climate scenarios indicates a direct link between the extent of warming and the frequency and severity of atmospheric river conditions.

What does this mean?

The significance of the study is two-fold.

First, "knowing the nature of how these atmospheric river events might change with future climate conditions allows for scientists, water managers, stakeholders and citizens living in atmospheric river-prone regions [e.g. western N. America, western S. America, S. Africa, New Zealand, western Europe] to consider the potential implications that might come with a change to these extreme precipitation events," said Vicky Espinoza, postdoctoral fellow at the University of California-Merced and first author of the study.

And secondly, the study and its approach provide a much-needed, uniform way to research atmospheric rivers on a global level—illustrating a foundation to analyze and compare them that did not previously exist.

Limitations

Data across the models are generally consistent—all support the projection that atmospheric river conditions are linked to warming and will increase in the future; however, co-author Marty Ralph of the University of California, San Diego, points out that there is still work to be done.

"While all the models project increases in the frequency of atmospheric river conditions, the results also illustrate uncertainties in the details of the climate projections of this key phenomenon," he said. "This highlights the need to better understand why the models' representations of atmospheric rivers vary."

The study, titled "Global Analysis of Climate Change Projection Effects on Atmospheric Rivers," was recently published in the journal Geophysical Research Letters.


Explore further

Atmospheric rivers linked to severe precipitation in Western Europe

More information: Vicky Espinoza et al. Global Analysis of Climate Change Projection Effects on Atmospheric Rivers, Geophysical Research Letters (2018). DOI: 10.1029/2017GL076968
Journal information: Geophysical Research Letters

Provided by NASA
Citation: Climate change may lead to bigger atmospheric rivers (2018, May 25) retrieved 27 June 2019 from https://phys.org/news/2018-05-climate-bigger-atmospheric-rivers.html
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May 25, 2018
Unfortunately this will not halt the U.S. grain belt reverting to a desert.

nsidc.org/arcticseaicenews/charctic-interactive-sea-ice-graph/

May 25, 2018
Is there no end to this shameless fear mongering?
When will phys.org stop spreading this blatant and contrived, propaganda?

May 25, 2018
Go to hell, Rodkeh. You're the only propogandist here. Tell me when you publish proof of anything you denialists have ever claimed.

May 28, 2018
Unfortunately this will not halt the U.S. grain belt reverting to a desert.
nsidc.org/arcticseaicenews/charctic-interactive-sea-ice-graph/

Any particular reason you choose the U.S. grain belt? It wasn't desert when the white man got here and it won't be desert when he's gone but nobody will be raising grain using irrigation here in a few years, that's for sure.
However, if we spent less on hand-held devices so people can play games, check their friends' relationship status, look at porn, and instead launch an Apollo Program/Manhattan Project/Interstate Highway/Transcontinental Railroad/Land Grant College level endeavor to sequester flood waters, filter and treat them, and pump them back underground into the natural storage banks there, with our improved methods of more efficient irrigation we could still raise plenty of food in the places spared destructive storms in any given year.
Too bad we don't have the will or the leadership to do those kinds of things anymore.

May 28, 2018
Oh yeah, those two things are linked. Not the rise of large-scale corporate donors who have hijacked your political systems to divert public funds to their own coffers. It's cat videos.

May 28, 2018
Oh yeah, those two things are linked. Not the rise of large-scale corporate donors who have hijacked your political systems to divert public funds to their own coffers. It's cat videos.


Is that directed at my comment? Based on the other comments it must be but I didn't say anything about cat videos, and my point is the amount of money we spend on things we don't need using money we don't have instead of acting in our collective and enlightened self interest to prepare for the inevitability of climate change in the future. Consumerism is now a more powerful opiate of the masses than religion and its spread preceded the takeover of the political system by the corporate donors by several decades. In fact it facilitated that takeover. And if corporations-- and consumerism-- are not taking over the political system wherever you live and sending the masses blissfully down the path of ignorance and apathy then good for you, and are you accepting immigrants?

May 29, 2018
These atmospheric rivers, pales in comparison to the River's of Bullshit, that the AGW Cult feeds it's ignorant Chicken Littles.

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