LOS ANGELES -- As back-to-back atmospheric rivers have made umbrellas a necessity across California -- and with more rain on the way in the state this weekend -- a new study reveals the connection between the weather phenomenon and the economic effects of localized flooding.
Atmospheric rivers, the storms that carry moisture from the tropics to the mid-latitude regions, have long been linked to the ecological impacts they have on a region. But when the storm passes, what's left in its wake?
In a study published Wednesday in Science Advances, researchers found that from 1978 to 2017, atmospheric rivers accounted for $42.6 billion in flood damage in 11 Western states -- 84% of the estimated total water-related damage of $50.8 billion. That's roughly $1.1 billion in damage done by atmospheric rivers every year.
"Research has shown that these storms are going to become more intense over the coming decades," said Tom Corringham, one of the authors of the study by the Scripps Institution of Oceanography at the University of California, San Diego and the U.S. Army Corps of Engineers.
Atmospheric rivers are a concentrated line of water vapor in the middle and lower atmospheric levels. The continuous stream of moisture pushes across the ocean until it encounters an obstacle, such as the coastal ranges of the West, which then causes the atmospheric river to unleash its load of moisture.
Some atmospheric rivers are weak and produce beneficial rain, helping vanquish devastating droughts.
In 2016, a series of larger atmospheric rivers helped ease California's epic drought by producing record rain and snow in the northern part of the state.
Just a few atmospheric river events can provide West Coast states such as California with a third to half of their annual precipitation, increasing snowpack levels and filling basins. A strong atmospheric river can carry 7 1/2 to 15 times the average flow of liquid water at the mouth of the Mississippi River. In fact, Corringham says he's working on a new study examining the benefits of the moisture-rich storms as they replenish water supplies.
But larger, more destructive atmospheric rivers can cause extreme rainfall, floods and mudslides.
On average, 30% to 50% of the West Coast's annual precipitation comes from a few atmospheric rivers each year. And the new data conclude that 99% of all flood damage in the Western coastal states of California, Oregon and Washington was caused by atmospheric rivers.