Evolution of potential vorticity in tropical cyclones

Wayne, H.; Schubert,; Alworth, Brian T.

doi:10.1002/qj.49711347509

Cited by 55 publications

(19 citation statements)

References 24 publications

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“…Eliassen's seminal work was later developed to investigate tropical cyclone dynamics from the point of view of PV (e.g., see, Schubert, 2018, and references therein). In the following, we will rely on a framework introduced for tropical cyclones by Schubert and Alworth (1987) and Schubert (2018), adapting it to the case of ATPs.…”

Section: Potential Vorticity Budget Of An Axisymmetric Flowmentioning

confidence: 99%

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Dynamics of diabatically forced anticyclonic plumes in the stratosphere

Podglajen,

Legras,

Lapeyre

et al. 2024

Quart J Royal Meteoro Soc

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A new class of vortices has been observed in the stratosphere following extreme wildfires (Canada 2017, Australia 2020) and volcanic eruptions (Raikoke 2019). These vortices are long‐lived mesoscale anticyclones (hundreds to 1,000 km in diameter) trapping plumes of aerosols and combustion/volcanic compounds. Owing to their unusual composition, these anticyclonically trapped plumes (ATPs) are associated with a significant radiative heating, which fuels their ascent through the stratosphere. This article investigates the dynamics of ATPs using two complementary approaches: analytically, in a potential vorticity (PV) perspective, and through idealised numerical simulations with the Weather Research and Forecasting (WRF) model. In both cases, we consider the vortical flow forced by a heating Lagrangian tracer. By reformulating the problem in the potential radius–potential temperature coordinate system introduced for tropical cyclones, we first clarify that ATP formation is concomitant with the injection of air into the stratosphere at extratropical latitudes. Then, we derive a set of simplified one‐dimensional equations describing the subsequent evolution of the flow after the injection. The equation obtained for the tracer is a variant of the classical Burgers' equation. In qualitative agreement with the three‐dimensional WRF simulations, this theoretical model predicts that ATPs develop an upper tracer front associated with sustained near‐zero anticyclonic PV, followed by a smooth tracer tail of cyclonic PV. Radiative relaxation of the temperature perturbations induced by the anticyclone and the presence of an initial PV anomaly tend to stabilise ATPs during their ascent. Finally, we note that the theory predicts a similar relationship between the plume and anticyclonic PV for cooled ATPs, which is supported by three‐dimensional simulations and may apply to the 2022 Hunga volcanic plume.

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Section: Potential Vorticity Budget Of An Axisymmetric Flowmentioning

confidence: 99%

“…Another derivation of this equation, starting directly from Equation (2), is provided in Schubert and Alworth (1987). Note that the form of Equation ( 11) a priori guarantees thatP remains single-signed.…”

Section: Pv In a Transformed Coordinate Systemmentioning

confidence: 99%

Dynamics of diabatically forced anticyclonic plumes in the stratosphere

Podglajen,

Legras,

Lapeyre

et al. 2024

Quart J Royal Meteoro Soc

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“…According to Schubert and Alworth (1987), the projection of Equation 1 on the potential radius coordinates…”

Section:  mentioning

confidence: 99%

“…The estimated winds are validated with dropsonde observations conducted in the T-PARCII project. A formulation of the azimuthally averaged vertical vorticity equation on the potential radius coordinate (Schubert & Alworth, 1987;Schubert & Hack, 1983) is used to isolate the asymmetric eddies because axisymmetric radial advection of the vorticity is not explicitly included in the equation. Based on the projection of the vorticity retrieved by the satellite-based tangential winds on the potential radius, roles of asymmetric processes in the inner eyewall dissipation are discussed.…”

mentioning

confidence: 99%

Inner‐Core Wind Field in a Concentric Eyewall Replacement of Typhoon Trami (2018): A Quantitative Analysis Based on the Himawari‐8 Satellite

et al. 2021

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Dynamics of rapid changes of intensity and structure in an eyewall replacement cycle of tropical cyclones remain an open question. To clarify the dynamics of the inner eyewall decaying, a quantitative estimation of inner‐core wind fields based on highly frequent observation images with 2.5‐min temporal resolution in the Himawari‐8 satellite is applied to Typhoon Trami (2018) which had a clear concentric eyewall structure. A high tangential wind of 50 m s−1 is estimated at a radius of 30 km, which is located in the inner edge of the inner eyewall, during an active stage of the inner eyewall. During the decaying stage of the inner eyewall, the estimated tangential wind rapidly decreases to about 20 m s−1 at a radius of 24 km. The satellite‐based tangential winds are validated with dropsondes around the inner core by an aircraft. Vorticity field retrieved by the satellite‐based tangential winds during the decaying stage exhibits a rapid decrease in an outer part of the eye and the inner eyewall, and a slow decrease near the storm center. Examination on an absolute angular momentum coordinate indicates that the rapidly slow‐down rotation in the outer edge of the eye and inner eyewall is faster than a slow‐down rotation explained by surface friction. It suggests that asymmetric eddies transport angular momentum across the moat in the inner eyewall dissipation. This study is the first examination of dynamical contributions of asymmetric eddies to the inner‐eyewall dissipation based on satellite‐estimated tangential winds.

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“…PV production in the TC eyewall can be particularly rapid because the dot product of the absolute vorticity vector and gradient of diabatic heating is very large there [28]. Because of this rapid PV production, very large values of PV have been simulated [29,30] and observed [31,32] in the hurricane inner-core region. As TCs have highly curved flow, the appropriate horizontal balance is nonlinear balance.…”

Section: Introductionmentioning

confidence: 99%

Forced, Balanced, Axisymmetric Shallow Water Model for Understanding Short-Term Tropical Cyclone Intensity and Wind Structure Changes

2021

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A minimal modeling system for understanding tropical cyclone intensity and wind structure changes is introduced: Shallow Water Axisymmetric Model for Intensity (SWAMI). The forced, balanced, axisymmetric shallow water equations are reduced to a canonical potential vorticity (PV) production and inversion problem, whereby PV is produced through a mass sink (related to the diabatic heating) and inverted through a PV/absolute angular momentum invertibility principle. Because the invertibility principle is nonlinear, a Newton–Krylov method is used to iteratively obtain a numerical solution to the discrete problem. Two versions of the model are described: a physical radius version which neglects radial PV advection (SWAMI-r) and a potential radius version that naturally includes the advection in the quasi-Lagrangian coordinate (SWAMI-R). In idealized numerical simulations, SWAMI-R produces a thinner and more intense PV ring than SWAMI-r, demonstrating the role of axisymmetric radial PV advection in eyewall evolution. SWAMI-R always has lower intensification rates than SWAMI-r because the reduction in PV footprint effect dominates the peak magnitude increase effect. SWAMI-r is next demonstrated as a potentially useful short-term wind structure forecasting tool using the newly added FLIGHT+ Dataset azimuthal means for initialization and forcing on three example cases: a slowly intensifying event, a rapid intensification event, and a secondary wind maximum formation event. Then, SWAMI-r is evaluated using 63 intensifying cases. Even though the model is minimal, it is shown to have some skill in short-term intensity prediction, highlighting the known critical roles of the relationship between the radial structures of the vortex inertial stability and diabatic heating rate. Because of its simplicity, SWAMI simulations are completed in seconds. Therefore, they may be of some use for hurricane nowcasting to short-term (less than 24 h) intensity and structure forecasting. Due to its favorable assumptions for tropical cyclone intensification, a potential use of SWAMI is a reasonable short-term upper-bound intensity forecast if the storm intensifies.

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Evolution of potential vorticity in tropical cyclones

Cited by 55 publications

References 24 publications

Dynamics of diabatically forced anticyclonic plumes in the stratosphere

Dynamics of diabatically forced anticyclonic plumes in the stratosphere

Inner‐Core Wind Field in a Concentric Eyewall Replacement of Typhoon Trami (2018): A Quantitative Analysis Based on the Himawari‐8 Satellite

Forced, Balanced, Axisymmetric Shallow Water Model for Understanding Short-Term Tropical Cyclone Intensity and Wind Structure Changes

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