The Wildhorse grass fire in eastern Idaho erupted with a large pulse of smoke. No one had expected it, but the wildfire had launched what’s known as a pyrocumulonimbus cloud, or pyroCb.
Pyrocumulonimbus clouds rise above intense fires, producing lightning and rain along with powerful winds that can whip the flames below into an anger. The largest pyroCbs funnel smoke 30,000 to 50,000 feet above Earth’s surface, as high as the cruising altitudes of commercial jets and even into the stratosphere.
Despite their large size, pyroCb clouds remain mysterious.
“We still do not understand if they’re driven by fire energetics, or fire intensity, or by atmospheric conditions above,” said Olga Kalashnikova, a researcher with NASA’s Jet Propulsion Laboratory in Southern California, who is one of the principal investigators leading INSPYRE, the first aircraft campaign designed specifically around studying pyroCbs.
For six weeks this summer, INSPYRE researchers climbed aboard a Gulfstream jet for a series of flights from the plane's home base at the National Center for Atmospheric Research near Boulder, Colorado.
NASA’s high-flying ER-2 aircraft, loaded with 14 instruments, tracked fire intensity, updraft speeds, smoke, and cloud properties from above, while crews drove trucks equipped with sensors to view the same events from the ground. The team will investigate how wildfire-generated clouds transport smoke upward, how clouds transform particles and gases in smoke, how much reaches the stratosphere, and what happens once it gets there.
“A unique thing about pyrocumulonimbus is they are fire-generated weather, meaning the fire makes its own weather,” said Neil Lareau, an atmospheric scientist at the University of Nevada, Reno, who led INSPYRE’s ground observations.