- Title: EXPLAINER: What are atmospheric rivers and why do they cause flooding?
- Date: 21st November 2024
- Summary: COLLEGE PARK, MARYLAND, UNITED STATES (NOVEMBER 21, 2024) (REUTERS) (SOUNDBITE) (English) ALLISON SANTORELLI, ACTING WARNING COORDINATION METEOROLOGIST FOR THE NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION (NOAA) WEATHER PREDICTION CENTER, SAYING: "Most notably Northern California seeing the heaviest impacts. Some locations have already over the past day or two, picked up as much as 6 to 12 inches of rain, and they could see another 3 to 6 isolated ten inches before all is said and done." SAN FRANCISCO, CALIFORNIA, UNITED STATES (NOVEMBER 20, 2024) (REUTERS) VARIOUS OF SAN FRANCISCO PUBLIC WORKS EMPLOYEES LOADING SANDBAGS
- Embargoed: 5th December 2024 19:41
- Keywords: ATMOSPHERIC RIVER CLIMATE CHANGE FLOODING
- Location: IN SPACE / SHORELINE, WASHINGTON / COLLEGE PARK, MARYLAND / SAN FRANCISCO, CALIFORNIA, UNITED STATES
- City: IN SPACE / SHORELINE, WASHINGTON / COLLEGE PARK, MARYLAND / SAN FRANCISCO, CALIFORNIA, UNITED STATES
- Country: US
- Topics: Disaster/Accidents,Floods,North America
- Reuters ID: LVA004155121112024RP1
- Aspect Ratio: 16:9
- Story Text: A powerful atmospheric river pounded Washington state on Wednesday (November 20), knocking out power to hundreds of thousands of people while disrupting road travel and causing at least two deaths and two injuries.
WHAT IS AN ATMOSPHERIC RIVER?
This weather system occurs all over the world. It starts when a large amount of water vapor from tropical oceans is carried by a jet stream toward land. As the air rises, it cools and condenses, resulting in rain or snow.
They most commonly form in mid-latitude oceans, roughly 30 and 60 degrees north and south, according to NASA. They appear as a trail of wispy clouds that can stretch for hundreds of miles.
HOW DO ATMOSPHERIC RIVERS CAUSE FLOODING?
Most atmospheric rivers are weak and do not cause damage. In fact, they can provide much-needed rain or snow. Atmospheric rivers can carry up to 15 times the volume of the Mississippi River, according to the National Oceanic and Atmospheric Administration. In drought-stricken California, such storms have triggered mudslides, toppled utility poles and blocked roadways, but also helped replenish depleted reservoirs and reduced the risk of wildfires by saturating the state's parched vegetation.
In 2019, an atmospheric river nicknamed the "Pineapple Express" hit California. The water vapor from near Hawaii brought rain and triggered mudslides that forced motorists to swim for their lives and sent homes sliding downhill.
In 2021, an atmospheric river dumped a month's worth of rain on British Columbia in two days, prompting deadly floods and landslides, devastating communities and severing access to Canada's largest port.
HOW WILL CLIMATE CHANGE IMPACT ATMOSPHERIC RIVERS?
Atmospheric rivers of the kind that drenched California and flooded British Columbia in recent years will become larger - and possibly more destructive - because of climate change, according to scientists.
Columns in the atmosphere hundreds of miles (km) long carry water vapor over oceans from the tropics to more temperate regions in amounts more than double the flow of the Amazon River, according to the American Meteorological Society.
There are projected to be 10% fewer atmospheric rivers in the future, but they are expected to be 25% wider and longer and carry more water, according to a 2018 research paper. This could make managing water supply much harder as moderate atmospheric rivers, which can be beneficial for water supplies, will be less frequent, and strong ones could become more calamitous.
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