On the Relative Contribution of Inertia–Gravity Wave Radiation to Asymmetric Instabilities in Tropical Cyclone–like Vortices
| Autor: | M. K. Yau, David A. Schecter, Konstantinos Menelaou |
|---|---|
| Rok vydání: | 2016 |
| Předmět: |
Physics
Atmospheric Science 010504 meteorology & atmospheric sciences Rossby wave Mechanics Atmospheric sciences 01 natural sciences Instability 010305 fluids & plasmas Vortex symbols.namesake Potential vorticity Barotropic fluid 0103 physical sciences Froude number symbols Gravity wave Tropical cyclone Physics::Atmospheric and Oceanic Physics 0105 earth and related environmental sciences |
| Zdroj: | Journal of the Atmospheric Sciences. 73:3345-3370 |
| ISSN: | 1520-0469 0022-4928 |
| DOI: | 10.1175/jas-d-15-0360.1 |
| Popis: | Intense atmospheric vortices such as tropical cyclones experience various asymmetric instabilities during their life cycles. This study investigates how vortex properties and ambient conditions determine the relative importance of different mechanisms that can simultaneously influence the growth of an asymmetric perturbation. The focus is on three-dimensional disturbances of barotropic vortices with nonmonotonic radial distributions of potential vorticity. The primary modes of instability are examined for Rossby numbers between 10 and 100 and Froude numbers in the broad neighborhood of unity. This parameter regime is deemed appropriate for tropical cyclone perturbations with vertical length scales ranging from the depth of the vortex to moderately smaller scales. At relatively small Froude numbers, the main cause of instability inferred from analysis typically involves the interaction of vortex Rossby waves with each other and/or critical-layer potential vorticity perturbations. As the Froude number increases from its lower bound, the main cause of instability transitions to inertia–gravity wave radiation. In some cases, the transition occurs abruptly at a critical point where a mode whose growth is driven almost entirely by radiation suddenly becomes dominant. In other cases, the transition is gradual and less direct as the fastest-growing mode continuously changes its structure. Examination of the angular pseudomomentum budget helps quantify the impact of radiation. The radiation-driven instabilities examined herein are shown to be quite fast and potentially relevant to real-world tropical cyclones. Their sensitivities to parameterized moisture and outer vorticity skirts are briefly addressed. |
| Databáze: | OpenAIRE |
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