Newly identified 'landfalling droughts' originate over ocean

September 24, 2020

Meteorologists track hurricanes over the oceans, forecasting where and when landfall might occur so residents can prepare for disaster before it strikes. What if they could do the same thing for droughts?

Stanford scientists have now shown that may be possible in some instances - the researchers have identified a new kind of "landfalling drought" that can potentially be predicted before it impacts people and ecosystems on land. They found that these droughts, which form over the ocean and then migrate landward, can cause larger and drier conditions than droughts that occur solely over the land. Of all the droughts affecting land areas worldwide from 1981 to 2018, roughly one in six were landfalling droughts, according to the study published Sept. 21 in

"We normally don't think about droughts over the ocean - it may even sound counterintuitive. But just as over land, there can be times where large regions in the ocean experience less rainfall than normal," said lead author Julio Herrera-Estrada, a research collaborator with Water in the West who conducted research for the study while he was a postdoctoral researcher at Stanford's School of Earth, Energy & Environmental Sciences (Stanford Earth). "Finding that some droughts start offshore will hopefully motivate conversations about the benefits of monitoring and forecasting droughts beyond the continents."

Droughts can harm or destroy crops, as well as impact water supplies, electricity generation, trade and ecosystem health. Historically, droughts have displaced millions of people and cost billions of dollars. Yet the climate processes that lead to drought are not fully understood, making accurate predictions difficult.

In order to pinpoint the large-scale landfalling droughts that originated over the ocean, the researchers used an object tracking algorithm to identify and follow clusters of moisture deficits all over the world, going back decades in time. They found that the landfalling droughts grew about three times as fast as land-only droughts, and usually took several months to reach a continent.

"Not all of the droughts that cause damage to humans and ecosystems are going to be these landfalling droughts," said study senior author and climate scientist Noah Diffenbaugh, the Kara J. Foundation Professor at Stanford Earth. "But there is something about the droughts that start over the ocean that makes them more likely to turn into large, intense events."

The researchers analyzed the physical processes of landfalling droughts in western North America, where a high frequency of them occur. They found that droughts that make landfall in the region have been associated with certain atmospheric pressure patterns that reduce moisture, similar to the "

The authors state that further analyses may reveal similar or new explanations for the landfalling droughts that they identified in other areas of the world, including Chile, Argentina, New Zealand and Eastern Australia.

"Our paper shows that landfalling droughts are a global phenomenon that affects every continent," Herrera-Estrada said. "There will definitely be a need for other studies to focus more on the physical processes relevant for each individual region."

Because of the large humanitarian and economic impacts of severe droughts, the potential for forecasting landfalling droughts may warrant further investigation, according to the researchers.

"This is an important finding because these landfalling droughts are statistically likely to be larger and more severe relative to non-landfalling droughts," said Diffenbaugh, who is also the Kimmelman Family Senior Fellow at the Stanford Woods Institute for the Environment. "Because they usually take a number of months to migrate onto land, there is a potential that tracking moisture deficits over the ocean could provide advance warning to help protect against at least some of the most severe droughts."
Diffenbaugh is also an affiliate of the Precourt Institute for Energy. Herrera-Estrada is currently an applied scientist at Descartes Labs, Inc.

The research was supported by the U.S. Department of Energy and Stanford University.

Stanford University

Related Droughts Articles from Brightsurf:

Expect more mega-droughts
Mega-droughts - droughts that last two decades or longer - are tipped to increase thanks to climate change, according to University of Queensland-led research.

One-two punch
Drought is endemic to the American West along with heatwaves and intense wildfires.

Droughts are threatening global wetlands: new study
University of Adelaide scientists have shown how droughts are threatening the health of wetlands globally.

Disastrous duo: Heatwaves and droughts
Simultaneous heatwaves and droughts are becoming increasingly common in western parts of the Unites States, according to a new study led by researchers from McGill University.

Newly identified 'landfalling droughts' originate over ocean
Researchers have identified a new type of 'landfalling drought' that originates over the ocean before traveling onto land, and which can cause larger, drier conditions than other droughts.

Combined droughts and heatwaves are occurring more frequently in several regions across the US
The frequency of combined droughts and heatwaves -- which are more devastating when they occur in unison -- has substantially increased across the western US and in parts of the Northeast and Southeast over the past 50 years, according to a new study.

Droughts in the Amazon rainforest can be predicted up to 18 months in advance
For the first time, it is possible to accurately predict severe drought up to 18 months in advance in Tropical South America.

Songbirds reduce reproduction to help survive drought
New research from the University of Montana suggests tropical songbirds in both the Old and New Worlds reduce reproduction during severe droughts, and this - somewhat surprisingly -- may actually increase their survival rates.

Small trees offer hope for rainforests
Small trees that grow up in drought conditions could form the basis of more drought-resistant rainforests, new research suggests.

Latest climate models show more intense droughts to come
An analysis of new climate model projections by Australian researchers from the ARC Centre of Excellence for Climate Extremes shows southwestern Australia and parts of southern Australia will see longer and more intense droughts due to a lack of rainfall caused by climate change.

Read More: Droughts News and Droughts Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to