NASA aircraft observations released on September 29 show a short-lived pileus cloud above a pyrocumulus rising from Montana’s Sand Creek fire. Visible and infrared images distinguish the burning area, smoke plume and thin upper layer in the same event. The cap was clear in only one frame from a sequence spaced roughly half an hour apart. A single scene cannot establish a long-term climate trend.
Science··Morning
Aircraft caught the thin layer above the fire
NASA’s ER-2 research aircraft recorded an unusual cloud layer while flying over the Sand Creek fire in Montana on August 11. The detailed observation was released on September 29. Heated air rose above the fire and built a smoke-filled pyrocumulus; a thin, smooth pileus appeared above it. That upper layer was a distinct condensation feature rather than the main fire cloud. The flight was part of the INSPYRE effort to study smoke and clouds generated by wildfires. The new development is the analysis of a transient structure caught during that flight, not the start of the fire.[1]
Visible and infrared bands separate the layers
The MASTER instrument on the aircraft showed the cloud’s shape in visible light. Shortwave infrared helped distinguish active fire spots from the burned perimeter, and downward-looking radars probed cloud structure. In the researchers’ explanation, the rising pyrocumulus pushed a moister layer overhead upward like a mountain; cooling air condensed into the thin cap. Different measurements collected during the same flight allowed the team to examine the vertical relation between the surface fire and the upper cloud. The images alone do not measure the speed of every current inside the fire cloud.[1]
One clear frame points to a brief lifetime
The pileus was clearly visible in only one image from a plume sequence taken at roughly half-hour intervals. That fits the brief lifetime such clouds can have, although the exact moments of formation and disappearance cannot be recovered from the spaced frames. At the moment of observation, the fire spread quickly along Mount Comet’s western slope. Winds aligned with terrain channels helped shape the rising plume. The observation documents a strong updraft and a transient cap in one particular fire. It cannot by itself establish a long-term climate trend or the behavior of every wildfire cloud.[1]
