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Thursday, September 3, 2009

Time lapse pyrocumulus for the LA “station” wildfire

Like volcanic eruptions, some fires grow large enough to make their own weather with the heat being released acting like convection. Witness this neat time lapse in HD showing the “Station” fire in the Angeles National Forest.


pyrocumulus_LA_fireclick for time lapse video


This video was made by photographer Brandon Riza on August 30th, 2009. It is quite well done and quite visually stunning. The station fire is also visible from space, and shows up in the AIRS satellite image shown below from NASA Goddard Space Flight Center.


AIRS_stationfireClick for a larger image


It is also visible by conventional satellite imagery.

Satimage_smoke_from_station_fire

The station fire in La Canada/Flintridge. Image Credit: NASA/GSFC/LaRC/JPL, MISR Team - Click for a larger image


For those interested, here is more information about pyrocumulus clouds.


h/t to “jeez” for the time lapse video


pyrocumulus—A pyrocumulus or fire cloud is a dense cumuliform cloud associated with fire or volcanic activity.


A pyrocumulus cloud is produced by the intense heating of the air from the surface. The intense heat induces convection which causes the air mass to rise to a point of stability, usually in the presence of moisture. Phenomena such as volcanic eruptions, forest fires, and occasionally industrial activities can induce formation of this cloud. The detonation of a nuclear weapon in the atmosphere will also produce a pyrocumulus in the form of a mushroom cloud which is made by the same mechanism. The presence of a low level jet stream can enhance its formation. Condensation of ambient moisture (moisture already present in the atmosphere) as well as moisture evaporated from burnt vegetation or volcanic outgassing occurs readily on particles of ash.

A pyrocumulus cloud from the August 2009 Station fire in southern California.

A pyrocumulus cloud from the August 2009 Station fire in southern California

Pyrocumulus cloud viewed from above.

Pyrocumulus cloud viewed from above


Pyrocumuli contain severe turbulence which also results in strong gusts at the surface which can exacerbate a large conflagration. A large pyrocumulus, particularly one associated with a volcanic eruption, may also produce lightning. This is a process not fully understood as of yet, but is probably in some way associated with charge separation induced by severe turbulence, and perhaps, by the nature of the particles of ash in the cloud. Large pyrocumuli can contain temperatures well below freezing, and the electrostatic properties of any ice that forms may also play a role. A pyrocumulus which produces lightning is actually a type of cumulonimbus, a thundercloud and is called pyrocumulonimbus.

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