7 September 2019 | New Scientist | 29Fire clouds
Photographer David Peterson,
US Naval Research LaboratoryTHIS sinister photo shows the sun
setting through thick smoke from
the massive Williams Flats wildfire
in the east of Washington state.
As well as the grey smoke, which is
what makes the sun look strange,
there are massive white clouds
called pyrocumulonimbus
caused by the fire’s heat.
The image was captured by
meteorologist David Peterson
from a NASA research plane.
There are very few photos of these
clouds, says Peterson, and hardly
any from above. His was taken at
8 pm on 8 August from a height
of 9 kilometres.
The flight was part of a
joint project by NASA and
the US’s National Oceanic and
Atmospheric Administration to
study how smoke from wildfires
affects air quality and climate. The
particles and chemicals in smoke
can have complex effects on
clouds, from absorbing the sun’s
heat to triggering the formation
of heat-reflecting clouds.
Pyrocumulonimbus clouds
can act as chimneys, carrying
large amounts of smoke up into
the lower stratosphere. Smoke
that rises this high can linger for
weeks or months, amplifying its
effects. In August 2017, fire-driven
thunderstorms in North America
pumped vast amounts of smoke
into the stratosphere that
remained for four months.
Peterson’s team estimated that
the smoke’s mass was comparable
to that emitted during the 2008
eruption of an Alaskan volcano
called Kasatochi.
Some researchers think
such massive storms could
become more common as the
world warms, so understanding
pyrocumulonimbus clouds is
more important than ever. ❚Michael Le PageFascinated by flames?
Discover the science of fire with Guillermo Rein
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