March 06, 2019

Fire-Driven Thunderstorms

Listen Later

2 minutes

In 2016 and 2017, wildfires in western Canada spawned thunderstorms

that ignited additional fires, in some cases tens of miles away from the

original fire. These fire-triggered

thunderstorms are technically known as pyrocumulonimbus clouds, or “pyroCb’s”.

The physics of pyroCb’s is complex.

When super-heated updrafts from an intense fire suck smoke, ash, burning

materials, and water vapor high into the air, these elements cool and form

so-called fire clouds that look and act like the cumulonimbus clouds associated

with classic thunderstorms. What is

different is that the heat and particulates in the smoke almost always arrest

the ability of the cloud to produce rain.

Instead, what remains is a lightning storm that moves across the

landscape, triggering more fires.

These PyroCb events appear to be happening far more often, producing

more energy, and erupting in places where they have never been seen

before. As the world warms, wildfires themselves

are becoming larger and hotter. In the

past decade, wildfires have been burning more than twice as many acres as they

did before the turn of the 21st century. Along with the growth in wildfire activity,

there has been an increase in PyroCb events, and there are now an average of 25

per year in western North America.

Apart from starting new fires, pyroCb’s also have similar effects as

moderate-sized volcanic eruptions. Smoke

and aerosols from wildfires can rise high into the stratosphere, where they can

linger for months. Eventually, the

particles carried aloft in the atmosphere do come down, dumping dangerous

chemicals on far flung regions of the earth.

But unlike volcanic eruptions, which are relatively rare events, pyroCb’s

are happening more and more each year.

**********

Web Links

Fire-Induced Storms: A New Danger from the Rise in Wildfires

Photo, posted July 31, 2013, courtesy of Loren Kerns via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

...more

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Earth Wise

By Randy Simon

4.7

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March 06, 2019

Fire-Driven Thunderstorms

Listen Later

2 minutes

In 2016 and 2017, wildfires in western Canada spawned thunderstorms

that ignited additional fires, in some cases tens of miles away from the

original fire. These fire-triggered

thunderstorms are technically known as pyrocumulonimbus clouds, or “pyroCb’s”.

The physics of pyroCb’s is complex.

When super-heated updrafts from an intense fire suck smoke, ash, burning

materials, and water vapor high into the air, these elements cool and form

so-called fire clouds that look and act like the cumulonimbus clouds associated

with classic thunderstorms. What is

different is that the heat and particulates in the smoke almost always arrest

the ability of the cloud to produce rain.

Instead, what remains is a lightning storm that moves across the

landscape, triggering more fires.

These PyroCb events appear to be happening far more often, producing

more energy, and erupting in places where they have never been seen

before. As the world warms, wildfires themselves

are becoming larger and hotter. In the

past decade, wildfires have been burning more than twice as many acres as they

did before the turn of the 21st century. Along with the growth in wildfire activity,

there has been an increase in PyroCb events, and there are now an average of 25

per year in western North America.

Apart from starting new fires, pyroCb’s also have similar effects as

moderate-sized volcanic eruptions. Smoke

and aerosols from wildfires can rise high into the stratosphere, where they can

linger for months. Eventually, the

particles carried aloft in the atmosphere do come down, dumping dangerous

chemicals on far flung regions of the earth.

But unlike volcanic eruptions, which are relatively rare events, pyroCb’s

are happening more and more each year.

**********

Web Links

Fire-Induced Storms: A New Danger from the Rise in Wildfires

Photo, posted July 31, 2013, courtesy of Loren Kerns via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

...more