What is an atmospheric river? Understanding the Flooding in British Columbia | Item


Climate change could worsen these weather events


  • Atmospheric rivers are also called AR.

  • They are narrow bands of water vapor in the atmosphere that usually start near the equator and travel across the world.

  • As moisture moves northward and hits land, it is often released in the form of rain or snow.

  • Smaller ARs are beneficial to the ecosystem, but larger ones can cause flooding and landslides.

  • On December 1, British Columbia was hit with its third RA in less than three weeks.

  • Keep scrolling to learn more about ARs. ⬇️ ⬇️ ⬇️

British Columbians are picking up the pieces after another giant rainstorm hit the province.

Places like Hope, British Columbia, received more than 100 millimeters of rain on Wednesday, a third of what they usually receive throughout November.

This kind of unique weather event has a name: It’s called an atmospheric river, or AR for short.

So far, there have been three RAs in British Columbia since November 13, contributing to widespread flooding and landslides.

Keep reading to find out exactly what an atmospheric river is and why climate change could make them worse.

The term “atmospheric river” or RA was first coined in 1998 by researchers in the United States, but the meteorological event had been observed before that date. (Image credit: Jonathan Hayward / The Canadian Press)

What is an atmospheric river?

An RA is a wide, narrow band of water vapor in the atmosphere that is pushed away from the equator by currents – or concentrated areas of wind.

Imagine a river in the sky.

This river can stretch for 1,600 kilometers, about the length of 146 football fields.

As the water vapor moves north, to a place like British Columbia, it has condensed into precipitation (rain or snow).

An AR can potentially dump a month of rain or snow in a few days.

Where on the planet do they occur?

RAs typically form in eight ocean regions around the world.

One of these regions is the west coast of North America, including British Columbia

An average of 30 atmospheric rivers arrive in British Columbia each year.

An advantage of atmospheric rivers is that smaller ones can replenish a region’s water supply, however larger ones can cause flooding and landslides. (Image credit: Jonathan Hayward / The Canadian Press)

How dangerous are they?

Smaller, less intense ARs are beneficial to the ecosystem because they can provide part of a region’s annual water supply.

Unfortunately, larger, more intense ARs can trigger damaging landslides and flooding.

Canada does not yet have an official rating system to measure the dangerousness of ARs.

But in 2019, American scientists developed a category scale for ARs, similar to that used for hurricanes.

They are classified by intensity – from AR1 (weakest) to AR5 (strongest).

Using this scale, recent storms in British Columbia are rated between AR4 and AR5, which means they are dangerous and potentially fatal to humans.

On November 18, members of the Canadian Forces arrived in British Columbia to help the province prepare for the planned RAs. (Image credit: Darryl Dyck / The Canadian Press)

Impact of climate change

Climate change is increasing average temperatures on Earth.

The warmer the air, the more water vapor there is in the atmosphere.

The more water vapor there is, the larger the AR and the more damage it is likely to cause.

As if that weren’t enough, there are also fewer trees in British Columbia to absorb the rain, in part because of the increasingly severe forest fires, also linked to climate change.

What are we doing to protect people from AR?

On November 20, Environment and Climate Change Canada (ECCC) announced the development of a new classification system for ARs, similar to that used in the United States.

The system would help scientists identify and track RAs early enough to alert people when an RA is on its way, so they can prepare.

It would also allow the authorities to take measures to prevent floods and other disasters.

ECCC said this early warning system should be in place by fall 2022.

You have more questions ? We will do our best to study it for you. Ask your parent or guardian for permission and email us at cbckidsnews@cbc.ca.

With files from The Canadian Press, What On Earth / CBC Radio
BEST IMAGE CREDIT: Jonathan Hayward / The Canadian Press


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