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AOSC Seminar by Dr. Morgan O'Neill, 09/03/2020

AOSC Seminar

Dr. Morgan O'Neill

Earth System Science, Stanford University

Title: Fujita's "jumping cirrus": hydraulic jump dynamics above supercell thunderstorms


The strongest supercell thunderstorms typically feature an Above-Anvil Cirrus Plume (AACP), which is a wake of ice and water vapor downstream of overshooting deep convection, several km above the large anvil shield. Thunderstorms are known to be an important source of water vapor to the lower stratosphere, with substantial implication for climate. Previous work has shown that the occurrence of the AACP is coincident with strong evidence of breaking gravity waves, but a more detailed study of its dynamics and lifecycle has not been undertaken. Using 50-m isotropic large eddy simulations, we show that the overshooting top of a supercell acts as a topographic obstacle and drives a hydraulic jump downstream. Stratospheric air that crests the effective topography plummets smoothly down the lee side at speeds exceeding 100 m/s and then quickly transitions to highly turbulent in a rapidly-evolving hydraulic jump. This jump injects water vapor and ice into the lower stratosphere irreversibly, several kilometers above the top of the anvil cloud, forming a distinct, realistic AACP. We provide the first study of a large-scale hydraulic jump in the absence of solid topography.

Contact: Jacob Wenegrat

AOSC Seminar

Pre-seminar refreshment: N/A
Seminar: 3:30-4:30pm, Zoom
Meet-the-Speaker: 4:30-5:00pm, Zoom [For AOSC Students only]

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