Atmosphere Ocean Science Colloquium

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A multi-scale, multi-layer theory for tropical cyclone intensification

Speaker: Rupert Klein, Freie Universtät Berlin

Location: Warren Weaver Hall 1314

Date: Tuesday, April 22, 2025, 11 a.m.

Synopsis:

An asymptotic triple-deck theory for vortices in gradient wind balance reveals a host of scale interactions which collectively are responsible for vortex intensification.As shown in earlier work, a strongly tilted bulk tropospheric vortex undergoes a self-induced meandering motion, coupled with the primary circulation dynamics through asymmetric heating and cooling patterns.Here we show, in the axisymmetric setting, that the vortex couples to the surface through a "convection-controlling layer" (CCL) and a friction layer (FL). Boundary layer convergence in the FL generates super-gradient winds, forces upward flow into the CCL, and establishes its moist and thermal energy distributions. The CCL hosts the lifting condensation level (LCL) and the level of free convection (LFC). By tapping into a necessary, though possibly moderate, level of CAPE, it triggers multiscale convection that funnels boundary layer air into the bulk flow.The detailed asymptotic analysis reveals how, mediated by these ingredients, angular momentum transport between the three layers induces vortex intensification