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What are atmospheric rivers and why are they so destructive?
STORY: A powerful atmospheric river pounded Washington state and the Pacific Northwest this week, killing at least two people, and knocking out power to hundreds of thousands. With temperatures around the world rising, scientists say these weather systems will become larger, and possibly more destructive. :: What is an atmospheric river? So what is an atmospheric river? Allison Santorelli, a meteorologist for the National Oceanic and Atmospheric Administration, breaks it down. “Atmospheric rivers are pretty much you can think of it as like a river in the sky. So a river transports, as we know, a river transports a lot of water. And so atmospheric rivers are essentially that just up in the sky. They’re relatively long, narrow regions with significant current water vapor that helps to transport moisture from the tropical areas into the mid-latitudes, which is where the United States is located.” Atmospheric rivers appear as a trail of wispy clouds that can stretch for hundreds of miles. As the water vapor in the jet stream rises, it cools and condenses, resulting in rain or snow. According to NOAA, an atmospheric river can carry 15 times the volume of the Mississippi River. :: Impact of rising temperaturesMost atmospheric rivers are weak and do not cause damage. In fact, they can provide much-needed rain or snow. A 2018 research paper projected there to actually be 10% fewer atmospheric rivers in the future. But that’s not necessarily a good thing: if moderate atmospheric rivers occur less frequently, it could make managing water supplies more difficult. And more bad news: the same study found that atmospheric rivers in coming years are expected to be 25% wider and longer and carry more water, potentially wreaking more havoc in vulnerable mid-latitude regions. Santorelli explains the part that rising global temperatures play in the equation. “So scientific research has shown that the climate is warming and average monthly to yearly temperatures are increasing. Now, while it’s difficult to say exactly how this might impact atmospheric rivers specifically, certainly we do know that warmer air is capable of holding more water vapor. And so it’s possible that a warming climate could result in stronger and more extreme weather.”