An Estimation of Turbulent Characteristics in the Low-Level Region of Intense Hurricanes Allen (1980) and Hugo (1989)

Zhang, Jun A.; Marks, Frank D.; Montgomery, Michael T.; Lorsolo, Sylvie

doi:10.1175/2010mwr3435.1

Cited by 126 publications

(129 citation statements)

References 67 publications

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“…For l v 1 ¼ 200 m and with k 00.4, we obtain l v 0100 m at z 0500 m. This agrees with the value derived by Zhang et al (2011) from aircraft data collected in the eyewall region of one category 4, and one category 5 hurricane. The computation of micro-turbulent atmosphereÁocean exchange is based on a commonly used bulk algorithm [cf.…”

Section: Parameterisation Of Subscale Processessupporting

confidence: 88%

Dynamical system properties of an axisymmetric convective tropical cyclone model

Schönemann¹,

Frisius

2014

Tellus A: Dynamic Meteorology and Oceanography

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A B S T R A C TThe dynamical system behaviour of tropical cyclones and their potential intensity with a view to sea surface temperature, tropospheric temperature stratification and tropospheric moisture content is investigated in the axisymmetric convective model HURMOD. The model results exhibit the existence of a fixed-point attractor associated with a strong tropical cyclone. Moreover, the initial vortex strength forms an amplitude threshold to cyclogenesis. Above this threshold, the size of the tropical cyclone and its intensity are independent of the initial vortex strength and its horizontal extent. Below the amplitude threshold, cyclogenesis does not occur and the system approaches an atmospheric state of rest. In case one allows for a deviation of the tropospheric stratification from moist-neutral conditions, the modelling results reveal the existence of bifurcations with the sea surface temperature representing the bifurcation parameter: As the sea surface temperature decreases and the storm weakens, the fixed-point attractor turns first into a limit cycle indicating a Hopf-bifurcation and then gives way to a steady-state of lower intensity, before the intensity oscillation becomes chaotic, and finally the tropical storm dies. The amplitude threshold and the sea surface temperature range, within which the system exhibits bifurcation points, are sensitive to the reference value of relative humidity and the reference tropospheric temperature stratification. If the reference troposphere is presumed to be moist-neutral, the dynamical behaviour of the modelled tropical cyclone does not change within the range of tropical sea surface temperature, and the tropical cyclone only slightly weakens with decreasing sea surface temperature, without any abrupt changes in intensity. Apart from the existence of Hopf-bifurcations, these findings are qualitatively similar to results gained from a low-order model presented in a precursory study.

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Section: Parameterisation Of Subscale Processessupporting

confidence: 88%

Dynamical system properties of an axisymmetric convective tropical cyclone model

Schönemann¹,

Frisius

2014

Tellus A: Dynamic Meteorology and Oceanography

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“…The sensitivity to K is problematic because the only observational estimates for this quantity that we are aware of are those analysed recently from flight-level wind measurements at an altitude of about 500 m in hurricanes Allen (1980) and Hugo (1989) by Zhang et al (2011b respectively. On the other hand, the other schemes have broadly realistic diffusivities.…”

Section: An Axisymmetric Balance View Of Spin-upmentioning

confidence: 99%

Paradigms for tropical cyclone intensification

Montgomery¹,

Smith²

2014

AMOJ

193

137

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We review the four main paradigms of tropical cyclone intensification that have emerged over the past five decades, discussing the relationship between them and highlighting their strengths and weaknesses. A major focus is on a new paradigm articulated in a series of recent papers using observations and highresolution, three-dimensional, numerical model simulations. Unlike the three previous paradigms, all of which assumed axial symmetry, the new one recognises the presence of localised, buoyant, rotating deep convection that grows in the rotation-rich environment of the incipient storm, thereby greatly amplifying the local vorticity. It exhibits also a degree of randomness that has implications for the predictability of local asymmetric features of the developing vortex. While surface moisture fluxes are required for intensification, the postulated 'evaporation-wind' feedback process that forms the basis of an earlier paradigm is not. Differences between spin up in three-dimensional and axisymmetric numerical models are discussed also.In all paradigms, the tangential winds above the boundary layer are amplified by the convectively-induced inflow in the lower troposphere in conjunction with the approximate material conservation of absolute angular momentum. This process acts also to broaden the outer circulation. Azimuthally-averaged fields from high-resolution model simulations have highlighted a second mechanism for amplifying the mean tangential winds. This mechanism, which is coupled to the first via boundary-layer dynamics, involves the convergence of absolute angular momentum within the boundary layer, where this quantity is not materially conserved, but where air parcels are displaced much further radially inwards than air parcels above the boundary layer. It explains why the maximum tangential winds occur in the boundary layer and accounts for the generation of supergradient wind speeds there. The boundary layer spin-up mechanism is not unique to tropical cyclones. It appears to be a feature of other rapidly-rotating atmospheric vortices such as tornadoes, waterspouts and dust devils and is manifest as a type of axisymmetric vortex breakdown. The mechanism for spin up above the boundary layer can be captured approximately by balance dynamics, while the boundary layer spin-up mechanism cannot. The spin-up process, as well as the structure of the mature vortex, are sensitive to the boundary-layer parameterisation used in the model.

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“…Investigations of turbulent spectra in the HBL (Yu et al 2008;Zhang 2010a;Zhang et al 2010;Li et al 2015) have relied on observations from less intense hurricanes (undergoing landfall), without an emphasis on turbine loads. Zhang (2010a) compared normalized spectra and cospectra of wind velocity, temperature, and humidity fluctuations to theoretical spectral curves over the land and ocean based on Monin-Obukhov similarity theory.…”

Section: Introductionmentioning

confidence: 99%

Using Large-Eddy Simulations to Define Spectral and Coherence Characteristics of the Hurricane Boundary Layer for Wind-Energy Applications

Worsnop

Bryan

Lundquist

et al. 2017

Boundary-Layer Meteorol

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Offshore wind-energy development is planned for regions where hurricanes commonly occur, such as the USA Atlantic Coast. Even the most robust wind-turbine design (IEC Class I) may be unable to withstand a Category-2 hurricane (hub-height wind speeds >50 m s −1 ). Characteristics of the hurricane boundary layer that affect the structural integrity of turbines, especially in major hurricanes, are poorly understood, primarily due to a lack of adequate observations that span typical turbine heights (<200 m above sea level). To provide these data, we use large-eddy simulations to produce wind profiles of an idealized Category-5 hurricane at high spatial (10 m) and temporal (0.1 s) resolution. By comparison with unique flight-level observations from a field project, we find that a relatively simple configuration of the Cloud Model I model accurately represents the properties of Hurricane Isabel (2003) in terms of mean wind speeds, wind-speed variances, and power spectra. Comparisons of power spectra and coherence curves derived from our hurricane simulations to those used in current turbine design standards suggest that adjustments to these standards may be needed to capture characteristics of turbulence seen within the simulated hurricane boundary layer. To enable improved design standards for wind turbines to withstand hurricanes, we suggest modifications to account for shifts in peak power to higher frequencies and greater spectral coherence at large separations.

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An Estimation of Turbulent Characteristics in the Low-Level Region of Intense Hurricanes Allen (1980) and Hugo (1989)

Cited by 126 publications

References 67 publications

Dynamical system properties of an axisymmetric convective tropical cyclone model

Dynamical system properties of an axisymmetric convective tropical cyclone model

Paradigms for tropical cyclone intensification

Using Large-Eddy Simulations to Define Spectral and Coherence Characteristics of the Hurricane Boundary Layer for Wind-Energy Applications

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