Turbulence in breaking mountain waves and atmospheric rotors estimated from airborne <i>in situ</i> and Doppler radar measurements

Strauss, Lukas; Serafin, Stefano; Haimov, S.; Grubı̆sı́c, Vanda

doi:10.1002/qj.2604

Cited by 51 publications

(69 citation statements)

References 57 publications

(98 reference statements)

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“…The latter has been traditionally described and schematically represented as horizontal vortices with an axis parallel to a mountain ridge (Grubi si c et al 2008) and are often characterized by severe or extreme turbulence Durran 2002, 2007;Strauss et al 2015). The interplay of baroclinic vorticity generation along stable layers embedded in mountain waves and shear vorticity generation within the terrain-adjoining boundary layer has been shown to exert a significant impact on the rotor structure and strength.…”

Section: Introductionmentioning

confidence: 99%

Wave-Induced Boundary Layer Separation in the Lee of the Medicine Bow Mountains. Part II: Numerical Modeling

Grubı̆sı́c

Serafin

Strauss

et al. 2015

Journal of the Atmospheric Sciences

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Mountain waves and rotors in the lee of the Medicine Bow Mountains in southeastern Wyoming are investigated in a two-part paper. Part I by French et al. delivers a detailed observational account of two rotor events: one displays characteristics of a hydraulic jump and the other displays characteristics of a classic leewave rotor. In Part II, presented here, results of high-resolution numerical simulations are conveyed and physical processes involved in the formation and dynamical evolution of these two rotor events are examined.The simulation results reveal that the origin of the observed rotors lies in boundary layer separation, induced by wave perturbations whose amplitudes reach maxima at or near the mountain top. An undular hydraulic jump that gave rise to a rotor in one of these events was found to be triggered by midtropospheric wave breaking and an ensuing strong downslope windstorm. Lee waves spawning rotors developed under conditions favoring wave energy trapping at low levels in different phases of these two events. The upstream shift of the boundary layer separation zone, documented to occur over a relatively short period of time in both events, is shown to be the manifestation of a transition in flow regimes, from downslope windstorms to trapped lee waves, in response to a rapid change in the upstream environment, related to the passage of a short-wave synoptic disturbance aloft.The model results also suggest that the secondary obstacles surrounding the Medicine Bow Mountains play a role in the dynamics of wave and rotor events by promoting lee-wave resonance in the complex terrain of southeastern Wyoming.

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Section: Introductionmentioning

confidence: 99%

Wave-Induced Boundary Layer Separation in the Lee of the Medicine Bow Mountains. Part II: Numerical Modeling

Grubı̆sı́c

Serafin

Strauss

et al. 2015

Journal of the Atmospheric Sciences

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“…Research aircraft are often not equipped to measure wind fluctuations with spatial resolution better than a few tens of meters (Wendisch and Brenguier, 2013). Due to various problems related to, for example, inhomogeneity of turbulence along the aircraft track and/or artifacts related to inevitable aerodynamic problems (Khelif et al, 1999;Kalgorios and Wang, 2002;Mallaun et al, 2015), estimates of at such low resolutions using power spectral density (PSD) or structure functions are complex and far from being standardized (e.g., compare procedures in Strauss et al, 2015;Jen-La Plante et al, 2016). The following question arises: can we do any better or can we at least introduce alternative methods to increase the robustness of retrievals?…”

Section: Introductionmentioning

confidence: 99%

Novel approaches to estimating the turbulent kinetic energy dissipation rate from low- and moderate-resolution velocity fluctuation time series

Wacławczyk

Kopeć

et al. 2017

Atmos. Meas. Tech.

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Abstract. In this paper we propose two approaches to estimating the turbulent kinetic energy (TKE) dissipation rate, based on the zero-crossing method by Sreenivasan et al. (1983). The original formulation requires a fine resolution of the measured signal, down to the smallest dissipative scales. However, due to finite sampling frequency, as well as measurement errors, velocity time series obtained from airborne experiments are characterized by the presence of effective spectral cutoffs. In contrast to the original formulation the new approaches are suitable for use with signals originating from airborne experiments. The suitability of the new approaches is tested using measurement data obtained during the Physics of Stratocumulus Top (POST) airborne research campaign as well as synthetic turbulence data. They appear useful and complementary to existing methods. We show the number-of-crossings-based approaches respond differently to errors due to finite sampling and finite averaging than the classical power spectral method. Hence, their application for the case of short signals and small sampling frequencies is particularly interesting, as it can increase the robustness of turbulent kinetic energy dissipation rate retrieval.

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“…Mountain waves, induced by stable tropospheric flow over terrain, are a well-known source of aviation hazards, such as strong up-and down-drafts, downslope windstorms [1][2][3][4], clear air turbulence (CAT) associated with tropospheric wave breaking [5][6][7][8][9][10], low-level turbulence and 'rotors' associated with wave-induced boundary layer separation [11][12][13][14][15][16][17] and hydraulic jump-like flows [12,18], as well as hazards to surface transport [19], such as very strong or gusty winds [20].…”

Section: Introductionmentioning

confidence: 99%

Mountain Waves in High Resolution Forecast Models: Automated Diagnostics of Wave Severity and Impact on Surface Winds

Sheridan

Brown

2017

Atmosphere

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An automated method producing a diagnostic of the severity of lee waves and their impacts on surface winds as represented in output from a high resolution linear numerical model (3D velocities over mountains (3DVOM)) covering several areas of the U.K. is discussed. Lee waves involving turbulent rotor activity or downslope windstorms represent a hazard to aviation and ground transport, and summary information of this kind is highly valuable as an efficient 'heads-up' for forecasters, for automated products or to feed into impact models. Automated diagnosis of lee wave surface effects presents a particular challenge due to the complexity of turbulent zones in the lee of irregular terrain. The method proposed quantifies modelled wind perturbations relative to those that would occur in the absence of lee waves for a given background wind, and diagnoses using it are found to be quite consistent between cases and for different ranges of U.K. hills. A recent upgrade of the operational U.K. limited area model, the U.K. Variable Resolution Model (UKV) used for general forecasting at the Met Office means that it now resolves lee waves, and its performance is here demonstrated using comparisons with aircraft-and surface-based observations and the linear model. In the future, automated diagnostics may be adapted to use its output to routinely produce contiguous mesoscale maps of lee wave activity and surface impacts over the whole U.K.

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Turbulence in breaking mountain waves and atmospheric rotors estimated from airborne in situ and Doppler radar measurements

Cited by 51 publications

References 57 publications

Wave-Induced Boundary Layer Separation in the Lee of the Medicine Bow Mountains. Part II: Numerical Modeling

Wave-Induced Boundary Layer Separation in the Lee of the Medicine Bow Mountains. Part II: Numerical Modeling

Novel approaches to estimating the turbulent kinetic energy dissipation rate from low- and moderate-resolution velocity fluctuation time series

Mountain Waves in High Resolution Forecast Models: Automated Diagnostics of Wave Severity and Impact on Surface Winds

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