Science Daily September 9, 2021
The strongest supercell thunderstorms typically feature an above-anvil cirrus plume (AACP), which is a plume of ice and water vapor in the lower stratosphere that occurs downwind of the ambient stratospheric flow in the lee of overshooting deep convection. AACP-origin hydration of the stratosphere has a poorly constrained role in ozone destruction and surface warming. A team of researchers in the US (Stanford University, University of Wisconsin) used large eddy simulations corroborated by radar observations to understand the physics of AACP generation. They showed that the overshooting top of a simulated supercell can act as a topographic obstacle and drive a hydraulic jump downstream at the tropopause, like a windstorm moving down the slope of a mountain but without solid topography. Once the jump is established, water vapor injection deep into the stratosphere may exceed 7 tons per second. Previous research has shown they’re easy to spot in satellite imagery, often 30 minutes or more before severe weather reaches the ground. Forecasters can issue more accurate warnings without relying on Doppler radar systems, which can be knocked out by wind and hail — and have blind spots even on good days. In many parts of the world, Doppler radar coverage is nonexistent…read more. TECHNICAL ARTICLE