Concepts, observations, and simulation of refractive index turbulence in the lower atmosphere

Wyngaard, J. C.; Seaman, Nelson L.; Kimmel, Shari J.; Otte, Martin J.; Di, Xaio; Gilbert, Kenneth E.

doi:10.1029/2000rs002380

Cited by 30 publications

(25 citation statements)

References 63 publications

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“…The capping inversion is the region between the mixed layer and the free troposphere and can have strongly negative modified refractivity gradients. Often the change in the gradient is quite pronounced, producing a ''sharp top'' that is discussed at length by Wyngaard et al [2001].…”

Section: Environmental Model H Envmentioning

confidence: 99%

Inversion for refractivity parameters from radar sea clutter

et al. 2003

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[1] This paper describes estimation of low-altitude atmospheric refractivity from radar sea clutter observations. The vertical structure of the refractive environment is modeled using five parameters, and the horizontal structure is modeled using six parameters. The refractivity model is implemented with and without an a priori constraint on the duct strength, as might be derived from soundings or numerical weather-prediction models. An electromagnetic propagation model maps the refractivity structure into a replica field. Replica fields are compared to the observed clutter using a squared-error objective function. A global search for the 11 environmental parameters is performed using genetic algorithms. The inversion algorithm is implemented on S-band radar sea-clutter data from Wallops Island, Virginia. Reference data are from range-dependent refractivity profiles obtained with a helicopter. The inversion is assessed (1) by comparing the propagation predicted from the radar-inferred refractivity profiles and from the helicopter profiles, (2) by comparing the refractivity parameters from the helicopter soundings to those estimated, and (3) by examining the fit between observed clutter and optimal replica field. This technique could provide near-real-time estimation of ducting effects. In practical implementations it is unlikely that range-dependent soundings would be available. A single sounding is used for evaluating the radar-inferred environmental parameters. When the unconstrained environmental model is used, the ''refractivity-from-clutter,'' the propagation loss generated and the loss from this single sounding, is close within the duct; however, above the duct they differ. Use of the constraint on the duct strength leads to a better match also above the duct.

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Section: Environmental Model H Envmentioning

confidence: 99%

Inversion for refractivity parameters from radar sea clutter

et al. 2003

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“…For smaller aspect ratios, the conservation equations become stochastic but their coupling with the LES equations yields only marginal improvements in the prediction of the nondimensional mean shear and mean temperature gradient profiles. Wyngaard et al (1998) conclude the form of the SGS model has a much greater impact on the overall LES predictive capabilities in the surface layer than the surface flux exchange rule. We utilize well-established algorithms to integrate the LES equations in (1).…”

Section: Les Equationsmentioning

confidence: 99%

“…The use of local surface exchange coefficients is an approximation but is supported by the analysis of Wyngaard et al (1998), who performed an in-depth study of surface flux conservation equations. In the limit of large-grid aspect ratio z 1 /D ( 1, where z 1 is the first model level, they find the conservation equations are in a state of local equilibrium justifying the usual practice of applying local MO rules.…”

Section: Les Equationsmentioning

confidence: 99%

“…This is explained by the budgets for total horizontal scalar flux. For example, Wyngaard et al (1971) shows assuming horizontal homogeneity and using the classic Reynolds decomposition that …”

Section: B Impacts Of Cooling Rate With Fixed Resolutionmentioning

confidence: 99%

“…The importance of the SBL is well appreciated in climate and weather modeling as these forecasts show great sensitivity to the form of their SBL parameterization (Holtslag et al 2013). Intermittent SBL turbulence is also important in numerous application areas-for example, electromagnetic wave propagation (Wyngaard et al 2001), interpreting observations collected from wind profilers (Muschinskii and Sullivan 2013), and air quality (Weil 2012).…”

Section: Introductionmentioning

confidence: 99%

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Turbulent Winds and Temperature Fronts in Large-Eddy Simulations of the Stable Atmospheric Boundary Layer

Sullivan

Weil

Patton

et al. 2016

Journal of the Atmospheric Sciences

120

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The nighttime high-latitude stably stratified atmospheric boundary layer (SBL) is computationally simulated using high-Reynolds number large-eddy simulation on meshes varying from 200 3 to 1024 3 over 9 physical hours for surface cooling rates C r 5 [0.25, 1] K h 21 . Continuous weakly stratified turbulence is maintained for this range of cooling, and the SBL splits into two regions depending on the location of the lowlevel jet (LLJ) and C r . Above the LLJ, turbulence is very weak and the gradient Richardson number is nearly constant: Ri ; 0:25. Below the LLJ, small scales are dynamically important as the shear and buoyancy frequencies vary with mesh resolution. The heights of the SBL and Ri noticeably decrease as the mesh is varied from 200 3 to 1024 3 . Vertical profiles of the Ozmidov scale L o show its rapid decrease with increasing C r , with L o , 2 m over a large fraction of the SBL for high cooling. Flow visualization identifies ubiquitous warm-cool temperature fronts populating the SBL. The fronts span a large vertical extent, tilt forward more so as the surface cooling increases, and propagate coherently. In a height-time reference frame, an instantaneous vertical profile of temperature appears intermittent, exhibiting a staircase pattern with increasing distance from the surface. Observations from CASES-99 also display these features. Conditional sampling based on linear stochastic estimation is used to identify coherent structures. Vortical structures are found upstream and downstream of a temperature front, similar to those in neutrally stratified boundary layers, and their dynamics are central to the front formation.

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Local Infrasound Variability Related to In Situ Atmospheric Observation

Kim

Rodgers

Seastrand³

2018

Geophysical Research Letters

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Local infrasound is widely used to constrain source parameters of near‐surface events (e.g., chemical explosions and volcanic eruptions). While atmospheric conditions are critical to infrasound propagation and source parameter inversion, local atmospheric variability is often ignored by assuming homogeneous atmospheres, and their impact on the source inversion uncertainty has never been accounted for due to the lack of quantitative understanding of infrasound variability. We investigate atmospheric impacts on local infrasound propagation by repeated explosion experiments with a dense acoustic network and in situ atmospheric measurement. We perform full 3‐D waveform simulations with local atmospheric data and numerical weather forecast model to quantify atmosphere‐dependent infrasound variability and address the advantage and restriction of local weather data/numerical weather model for sound propagation simulation. Numerical simulations with stochastic atmosphere models also showed nonnegligible influence of atmospheric heterogeneity on infrasound amplitude, suggesting an important role of local turbulence.

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Concepts, observations, and simulation of refractive index turbulence in the lower atmosphere

Cited by 30 publications

References 63 publications

Inversion for refractivity parameters from radar sea clutter

Inversion for refractivity parameters from radar sea clutter

Turbulent Winds and Temperature Fronts in Large-Eddy Simulations of the Stable Atmospheric Boundary Layer

Local Infrasound Variability Related to In Situ Atmospheric Observation

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