Quantifying the Dependence of Temperature and Refractive Index Structure Parameters on Atmospheric Stability using Direct and Large-Eddy Simulations

Abstract Large-eddy simulations (LESs) of free-convective to near-neutral boundary layers are used to investigate the surface-layer turbulence. The article focuses on the Monin–Obukhov similarity theory (MOST) relationships that relate the structure parameters of temperature and humidity to the surface fluxes of sensible and latent heat, respectively. Moreover, the applicability of local free convection (LFC) similarity scaling is studied. The LES data suggest that the MOST function for is universal. It is shown to be within the range of the functions proposed from measurement data. It is found that follows MOST if entrainment of dry air from the free atmosphere is sufficiently small. In this case the similarity functions for and are identical. If entrainment is significant, dissimilarity between the transport of sensible heat and moisture is observed and no longer follows MOST. In the free-convection limit the LFC similarity functions should collapse to universal constants. The LES data suggest values around 2.7, which is in agreement with the value proposed in the literature. As for MOST, the LFC similarity constant for becomes nonuniversal if entrainment of dry air is significant. It is shown that LFC scaling is applicable even if shear production of turbulence is moderately high.

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Parameter Sensitivity and Statistical Correlation Found in Atmospheric Turbulence Studies

Volume 2: Fluid Mechanics; Multiphase Flows ◽

10.1115/fedsm2020-20254 ◽

2020 ◽

Author(s):

Luis F. Rodriguez ◽

Vinod Kumar ◽

Arturo Rodriguez ◽

V. M. Krushnarao Kotteda ◽

V. S. Rao Gudimetla ◽

...

Keyword(s):

Turbulent Flow ◽

Atmospheric Turbulence ◽

Control Volume ◽

Large Eddy Simulations ◽

Index Structure ◽

Cfd Modeling ◽

Optical Parameters ◽

Cfd Modelling ◽

Area Of Interest ◽

Large Eddy

Abstract We have simulated atmospheric turbulence at several instances of possible laser propagation paths and turbulent flow regime regions within the area of interest. At a control volume that is in between two Hawaii mountains. We have applied statistical correlations between Large-Eddy Simulations results using CFD modeling and parametrizing optical variables of interest, such as refractive index structure function. By comparing our Large-Eddy Simulations with specified parameters against other Large-Eddy Simulations with almost all same parameters except for one allows us to perform a sensitivity study. To study the changes on how a parameter can affect other scenarios of Large-Eddy Simulations parametric studies. With the end goal of validating the capacity of a sensitivity analysis study using Large-Eddy Simulations versus other Large-Eddy Simulations by a way of simulating and parametrizing turbulent flow studies found in the field of CFD modeling. Allowing us to achieve our stochastic analysis by applying sensitivity studies to see how our distributions change as a function of different parameters, but one at a time. After a comparison between CFD modelling simulations we have found that after a complete parametric study, a correlation was formed between turbulent flow parameters and optical parameters of interest.

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Investigations of boundary layer structure, cloud characteristics and vertical mixing of aerosols at Barbados with large eddy simulations

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-15-22637-2015 ◽

2015 ◽

Vol 15 (16) ◽

pp. 22637-22699 ◽

Cited By ~ 1

Author(s):

M. Jähn ◽

D. Muñoz-Esparza ◽

F. Chouza ◽

O. Reitebuch

Keyword(s):

Boundary Layer ◽

Marine Boundary Layer ◽

Vertical Mixing ◽

Atmospheric Stability ◽

Large Eddy Simulations ◽

Inertial Subrange ◽

Trade Wind ◽

Lidar Data ◽

Large Eddy ◽

Wind Lidar

Abstract. Large eddy simulations (LES) are performed for the area of the Caribbean island Barbados to investigate island effects on boundary layer modification, cloud generation and vertical mixing of aerosols. Due to the presence of a topographically structured island surface in the domain center, the model setup has to be designed with open lateral boundaries. In order to generate inflow turbulence consistent with the upstream marine boundary layer forcing, we use the cell perturbation method based on finite amplitude perturbations. In this work, this method is for the first time tested and validated for moist boundary layer simulations with open lateral boundary conditions. Observational data obtained from the SALTRACE field campaign is used for both model initialization and a comparison with Doppler wind lidar data. Several numerical sensitivity tests are carried out to demonstrate the problems related to "gray zone modeling" when using coarser spatial grid spacings beyond the inertial subrange of three-dimensional turbulence or when the turbulent marine boundary layer flow is replaced by laminar winds. Especially cloud properties in the downwind area west of Barbados are markedly affected in these kinds of simulations. Results of an additional simulation with a strong trade-wind inversion reveal its effect on cloud layer depth and location. Saharan dust layers that reach Barbados via long-range transport over the North Atlantic are included as passive tracers in the model. Effects of layer thinning, subsidence and turbulent downward transport near the layer bottom at z ~ 1800 m become apparent. The exact position of these layers and strength of downward mixing is found to be mainly controlled atmospheric stability (especially inversion strength) and wind shear. Comparisons of LES model output with wind lidar data show similarities in the formation of the daytime convective plume and the mean vertical wind structure.

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