Email
Password
Remember meForgot password?
    Log in with Twitter

article imageAtmospheric rivers may increase flood risks by 80 percent

By Karen Graham     Nov 5, 2017 in Environment
In a first-of-its-kind study, the global effects and impact of atmospheric rivers on rainfall, flooding, and droughts have been estimated for the first time. The study reveals that in some regions, the risks can be increased by as much as 80 percent.
Many places around the globe depend on atmospheric rivers (ARs), narrow bands of water vapor in the atmosphere that are propelled by jets of air swirling high above the Earth, for access to water. ARs can carry water vapor across the planet’s oceans, on to the continents and as far as the polar regions.
These "rivers" can change weather conditions instantly, causing flooding in one region and drought-like conditions in another. Oxford University, in collaboration with NASA’s Jet Propulsion Laboratory and other researchers, attempted to look at the bigger picture by mapping the global network of these aerial rivers and the extent of their effect on the planet.
Persistently heavy rainfall across western and central Europe has swollen rivers and claimed victims...
Persistently heavy rainfall across western and central Europe has swollen rivers and claimed victims from at least four countries
Joel Saget, AFP
Atmospheric rivers can cause extreme weather events
As extreme weather events, ARs expose almost 300 million people annually to flooding and droughts. And while the overall numbers may seem small, the ARs still create an enormous impact. Think about this - A strong AR weather event can transport a volume of water vapor equal to 7.5–15 times the average flow of liquid water at the mouth of the Mississippi River.
Most readers will remember the "Pineapple Express" that battered California in February this year. The atmospheric river event produced evacuation orders, water rescues and dangerous flooding and mudslides, causing millions of dollars in damages and the lives of a number of people.
The AR event was dubbed the Pineapple Express because of its apparent ability to bring moisture from the tropics near Hawaii to the U.S. west coast. Actually, from 30 to 50 percent of the annual precipitation in the West Coast states in the U.S. occurs in just a few AR events, and this contributes to the region's water supply.
So while some regions of the globe depend on ARs to replenish needed water, these same events can also create sometimes devastating floods and other damages, including the destruction of critical infrastructure, loss of income or even death.
Rivers left their banks in the historic deluge.
Rivers left their banks in the historic deluge.
#Louisiana on Twitter
Findings from the study
Using a database of specialized satellite observations which represent only water vapor, and not winds, the researchers were able to create a picture of the volume of water generated, and the effect on stream flow, soil moisture and snow levels. In turn, they were then able to identify areas where ARs have a major impact on flooding or drought.
Homero Paltan, the study’s lead author and a researcher at Oxford’s School of Geography and the Environment, said: ‘By incorporating demographic data into our study, we have found that, globally, a large number of people are exposed to hazards that stem from atmospheric rivers. They have a considerable impact that we're only beginning to understand and measure.’
Precipitation from atmospheric rivers contributes to 22 percent of the Earth's total water flow. And in some regions, like the east and west coasts of North America, Southeast Asia, and New Zealand, ARs can contribute to as much as 50 percent of the water flow.
Drought has forced 7.8 million people across the whole of Ethiopia to rely on emergency food handout...
Drought has forced 7.8 million people across the whole of Ethiopia to rely on emergency food handouts to stay alive.
CHRIS STEIN, AFP
Globally, it was also found that ARs can increase the likelihood of flood or drought hazards. Flood hazards can be increased by up to 80 percent in areas where they are most common, and in areas where rivers have little influence, the chance of a drought can be increased by as much as 90 percent.
Duane Waliser, chief scientist of the Earth Science and Technology Directorate at NASA's Jet Propulsion Laboratory in Pasadena, California and the paper’s co-author, said: " The findings provide added impetus for considering improvements to our observing and modeling systems that are used for forecasting atmospheric rivers.’
The study, "Global Floods and Water Availability Driven by Atmospheric Rivers," was published in the journal, Geophysical Research Letters.
More about atmospheric rivers, Floods, Droughts, hydrological extremes, hydroclimatic variability