The azimuthally averaged boundary layer structure of a numerically simulated major hurricane

Abarca, Sergio F.; Montgomery, Michael T.; McWilliams, James C.

doi:10.1002/2015ms000457

Cited by 14 publications

(24 citation statements)

References 45 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…As discussed by Kepert [2010a] and Abarca et al [2015], the use of a SBL model in TC simulations can cause excessively strong inflow and too large of a departure from gradient wind balance. By mass continuity, this can manifest updrafts at the top of the BL that are stronger than those obtained with a height-resolving BL model.…”

Section: 1002/2016jd025317mentioning

confidence: 99%

See 1 more Smart Citation

Deep convection in elliptical and polygonal eyewalls of tropical cyclones

et al. 2016

View full text Add to dashboard Cite

In observations, tropical cyclones with cyclonically rotating elliptical eyewalls are often characterized by wave number 2 (WN2) deep convection located at the edge of the major axis. A simple modeling framework is used to understand this phenomenon, where a nondivergent barotropic model (NBM) is employed to represent the elliptical vortex in the free atmosphere, and an asymmetric slab boundary layer (SBL) model is used to simulate the frictional boundary layer (BL) underneath the free atmosphere. The interaction is one way in that the overlying cyclonic flow drives the BL, but the BL pumping does not feed back to the overlying flow. The nonlinear‐balanced pressure field from the NBM drives the winds in the SBL model, which then causes BL convergence and pumping near the eyewall. The strong updrafts at the edge of the major axis for the elliptic vortex in the BL are induced by the larger convergent radial wind from the asymmetric distribution of the pressure fields of the free atmosphere with noncircular vortex. The large radial inflow maintains the supergradient wind at the edge of the elliptical vortex. The results emphasize the cyclonic rotation of the WN2 feature of strong updrafts at the top of the BL from the local shock‐like BL radial wind structure. Similar radial profiles and strong BL top updrafts occur at the edges of higher‐order polygonal eyewalls with the magnitude of the peak updraft decreasing as the wave number structure of the vortex increases.

show abstract

Section: 1002/2016jd025317mentioning

confidence: 99%

“…Abarca et al . [] suggested that shock‐like structures are not found in the azimuthally averaged vortex BL. It is possible, however, that the shock‐like structure may occur locally in the BL and not in the azimuthally averaged structure.…”

Section: Introductionmentioning

confidence: 99%

Deep convection in elliptical and polygonal eyewalls of tropical cyclones

et al. 2016

View full text Add to dashboard Cite

show abstract

“…[7], namely the emergence of strong, non-Ekman-like nonlinearities near the base of the eyewall at the later stages of intensification, giving rise to strong supergradient winds, much stronger than those obtained from Ekman-like dynamics. This is the signature of the nonlinear spinup mechanism, which significantly increases the destructive power of a tropical cyclone.…”

Section: Resultsmentioning

confidence: 99%

“…Ref. [7] used a modestly high resolution cloud-permitting numerical simulation of an idealized tropical cyclone. We find the same to be true for the WRF model output used here (not shown).…”

Section: A Forced Axisymmetric Convective Ring Model Revisitedmentioning

confidence: 99%

“…Assumption (2) is questionable because the stress-free boundary condition implies that the disturbance flow at the lower boundary is subject to an artificial momentum source at the boundary. Finally, regarding assumption (3), although the neglect of F z is certainly acceptable for the system-scale vortex dynamics, recent work by [7] has shown that F r is, by contrast, not negligible-in fact comparable to F λ in the boundary layer, as is usual in rotating frictional boundary layers. Ref.…”

Section: A Forced Axisymmetric Convective Ring Model Revisitedmentioning

confidence: 99%

See 1 more Smart Citation

On the Applicability of Linear, Axisymmetric Dynamics in Intensifying and Mature Tropical Cyclones

Montgomery

Smith

2017

Fluids

View full text Add to dashboard Cite

Abstract:The applicability of linearized axisymmetric dynamics to the intensification and structure change of tropical cyclones is investigated. The study is motivated by recent work that presented axisymmetric solutions to the linearized, non-hydrostatic, vortex-anelastic equations of motion (the so-called 3DVPAS model). The work called into question the importance of a recently proposed nonlinear, system-scale boundary-layer spinup mechanism both in intensifying storms and in mature storms undergoing secondary eyewall formation. The issue is examined using a three-dimensional mesoscale simulation of an intensifying tropical cyclone, alongside the linear 3DVPAS model. Solutions to the linear model, for imposed eddy forcing terms derived from the mesoscale simulation, are shown to be valid only for short times (t < 1 h) in the inner-core region of the vortex. At later times, the neglected nonlinear terms become significant and the linear results invalid. It follows that the linear results cannot be used to describe all aspects of the tropical cyclone dynamics at later times. In particular, they cannot be used (a) to dismiss the importance of the nonlinear boundary-layer spinup mechanism, nor (b) to isolate the separate effects of diabatic heating from those of friction, within the nonlinear boundary layer at least. Such separation depends on the linear superposition principle, which fails whenever nonlinearity is important. Similar caveats apply to the use of another linear model, the traditional Sawyer-Eliassen balance model. Its applicability is limited not only by linearity, but also by its assumption of strictly balanced motion. Both are incompatible with nonlinear spinup.

show abstract

Moist Potential Vorticity Diagnosis of the Tropical Cyclone Boundary Layer: Influence of Roll Vortices

Dey

O’Neill

2022

Preprint

View full text Add to dashboard Cite

Physical processes determining the dynamic and thermodynamic structure of a tropical cyclone boundary layer (TCBL) are quite different from anywhere else in the atmospheric boundary layer due to the substantial contribution of latent heating and frictional convergence. These processes regulate the radial and vertical distributions of momentum and enthalpy fluxes that are closely related to storm development and intensification. Our current understanding of TCBL is limited by the number of observations in this region, and a majority of the observational studies assume an axisymmetric structure. Three-dimensional observations and numerical studies show that substantial asymmetric structure exists in the TCBL. This study investigates the link between the asymmetric structure and small-scale processes using a Moist Potential Vorticity (MPV) framework. The simulated TCBL is uniquely characterized as a region of negative MPV with a robust and coherent layer of high-magnitude negative MPV embedded within, referred to as the Potential Vorticity Minimum Layer (PVML). The PVML can interact with the local flow anomalies such as those associated with roll vortices provided they are vertically collocated. The small-scale dynamical processes set the thermodynamic structure inside the TCBL and this interplay modulates the height of the PVML. Since the height of the PVML combines information about the local wind and thermal structures using a materially conserved variable, it is a valuable proxy to study the evolving 'topography' of a simulated TCBL.

show abstract

The azimuthally averaged boundary layer structure of a numerically simulated major hurricane

Cited by 14 publications

References 45 publications

Deep convection in elliptical and polygonal eyewalls of tropical cyclones

Deep convection in elliptical and polygonal eyewalls of tropical cyclones

On the Applicability of Linear, Axisymmetric Dynamics in Intensifying and Mature Tropical Cyclones

Moist Potential Vorticity Diagnosis of the Tropical Cyclone Boundary Layer: Influence of Roll Vortices

Contact Info

Product

Resources

About