Supercell storm clouds act like atmospheric mountains

2021-09-09

Last week, the remnants of Hurricane Ida spawned tornadoes and high winds that tore across the northeastern United States, destroying buildings and taking dozens of lives. Now, scientists have identified a key feature of big storms that could make such extreme weather events easier to predict.

When most storms form, they stay in the troposphere, the layer of the atmosphere where the majority of our planet’s weather takes place. But occasionally, they “punch up” into the stratosphere, creating mountains of clouds that trail wispy formations called above-anvil cirrus plumes (AACPs). These high-flying clouds have been linked to high winds, hailstorms, and tornadoes on the ground.

To find out why, researchers combined lightning data, radar, and severe storm warnings to build a 3D visualization of AACPs. Their model revealed that—just like winds rushing over real mountains—stratospheric winds rush over the high-level clouds as if they were solid objects. This generates powerful, downward winds and turbulent events called hydraulic jumps, they report today in Science.

These plumed storms, which can inject more than 7 tons of water per second into the normally dry stratosphere, might also have an impact on our climate, the researchers write. Because water vapor acts as a greenhouse gas once it enters the stratosphere, it could lead to warming temperatures on Earth—which would in turn spur more supercell storms. Knowing how these storms work, and when and where they occur, could improve climate models—and give advanced warning to people on the ground.

science.org, 9 September 2021
; https://www.science.org