Northern California has been ravaged by fire this summer in one of its worst recorded wildfire seasons, along with the Northern Territories of Canada near Yellowknife.
The rest of the Western U.S. has been having a fairly mild fire season, but California has been plagued by brush fire after brush fire brought on by extreme drought and high temperatures.
One fire near Buffalo Lake in Canada's Northwest Territories was so intense, clouds from the fire were picked up by a NASA satellite. "While fire clouds occur with some regularity, it's rare for Aqua to capture images of such mature pyrocumulus clouds," NASA says. "Because of their orbits, Terra always crosses the equator in the morning and Aqua always crosses in the early afternoon (local time). Since pyrocumulus clouds are most developed in the late afternoon or evening, they tend to look small and immature in MODIS imagery."
In another instance, the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite was able to photograph a pyrocumulonimbus cloud at 11 a.m. on Aug. 2. This cloud was on the border between California and Oregon.
The two photographs captured by NASA show how rapidly the fire progressed and expanded. The Beaver Complex fire expanded most rapidly. It was made up of two fires, the Salt Creek and Gulch fires. The Beaver Complex fire began on July 31 and quickly spread across the border and into California, where it burned for several days. NASA described the clouds from the fire as "tall, cauliflower-shaped." The fire burned more than 100,000 acres of land.
Pyrocumulus clouds form because intense heat at the ground level makes air rise rapidly, usually after a wildfire happens or a volcano erupts. As the air rises, the condensation of water vapor causes the cloud to form; ash and smoke from the fire can cause the gray appearance of the cloud. Pyrocumulonimbus clouds are rarer, caused by extreme drafts that raise them higher than normal pyrocumulus clouds; these clouds can have rain and, sometimes, lightning.
Pyrocumulonimbus clouds are a health hazard to surrounding areas, NASA says, because they can spread pollutants and smoke into the atmosphere through wind. Their height gives them the ability to affect a large surrounding area, larger than normal fire smoke clouds. Scientists closely monitor these clouds so that they can keep an eye on air pollution and air quality.
So far, the fire season in California and the Northwest region has produced 352 fires, burning 7 million acres. Last year, there were only 228 fires in the fire season, and only 900,000 acres were burned. This year has been unusually bad.
The fires, which are 42 percent contained, have consumed at least 35,000 acres as of Wednesday, according to the LA Times.