368106 Hydraulic jump dynamics in an above anvil cirrus plume in a 50-m resolution simulated supercell

Tuesday, 14 January 2020
Hall B1 (Boston Convention and Exhibition Center)
Leigh Orf, Univ. of Wisconsin, Madison, WI; and M. O'Neill

Above-anvil cirrus plumes (AACPs) are protrusions of cloud ice above the anvil of some thunderstorms. AACPs may possibly serve as a visual indicator of especially strong convection, and also as a mechanism for the injection of water into the lower stratosphere that may catalyze the destruction of ozone. Previous work has shown that AACPs are associated with breaking gravity waves that may serve as a primary mechanism for injecting water into the stratosphere. Here we present results from an isotropic 50 m resolution CM1 simulation, spanning a domain of 120 km by 120 km by 30 km (2,400 x 2,400 x 600 or 3.5 billion grid volumes) with model output saved and visualized every 2 model seconds.

The overshooting top region extends as high as 19 km in the cloud ice field and develops a distinct, realistic AACP that undergoes a full lifecycle over the subsequent two hours. We show that the overshooting top of deep convection drives a hydraulic jump downstream. The overshooting air becomes negatively buoyant and plummets back into the anvil at speeds exceeding 80 m/s. The upper portion of the flow quickly transitions from supercritical to subcritical and 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. We compare the AACP hydraulic jump to the well-known hydraulic jump/rotor flow in the lee of mountain ranges. High definition visualizations of water vapor, cloud, ice, and momentum will be presented to elucidate the flow of the AACP and its forcing mechanisms.

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