Similarity theory and calculation of turbulent fluxes at the surface for the stably stratified atmospheric boundary layer

2007 ◽  
pp. 37-49 ◽  
Author(s):  
Sergej S. Zilitinkevich ◽  
Igor N. Esau
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Similarity Theory ◽  
Turbulent Fluxes

Atmospheric boundary layer turbulence in the presence of swell: turbulent kinetic energy budget, Monin-Obukhov similarity theory and inertial dissipation method

2020 ◽  
Author(s):  
Zhongshui Zou
Keyword(s):  
Boundary Layer ◽  
Kinetic Energy ◽  
Atmospheric Boundary Layer ◽  
Turbulent Kinetic Energy ◽  
Similarity Theory ◽  
Turbulent Transport ◽  
Ocean Waves ◽  
Turbulent Stress ◽  
Total Stress ◽  
Inertial Dissipation Method

<p><span>Turbulence over the mobile ocean surface has distinct properties compared to turbulence over land. This raises the issue of whether functions such as the turbulent kinetic energy (TKE) budget and Monin-Obukhov similarity theory (MOST) determined over land are directly applicable to ocean surfaces because of the existence of a wave boundary layer (the lower part of atmospheric boundary layer including effects of surface waves. We used the term “WBL” in this article for convenience), where the total stress can be separated into turbulent stress and wave coherent stress. Here the turbulent stress is defined as the stress generated by wind shear and buoyancy, and wave coherent stress accounts for the momentum transfer between ocean waves and atmosphere. In this study, applications of the turbulent kinetic energy (TKE) budget and the inertial dissipation method (IDM) in the context of the Monin-Obukhov similarity theory (MOST) within the WBL are examined. It was found that turbulent transport terms in the TKE budget should not be neglected when calculating the total stress under swell conditions. This was confirmed by observations made on a fixed platform. The results also suggested that turbulent stress, rather than total stress should be used when applying the MOST within the WBL. By combing the TKE budget and MOST, our study showed that the stress computed by the traditional IDM corresponds to turbulent stress rather than total stress. The swell wave coherent stress should be considered when applying the IDM to calculate the stress in the WBL.</span></p>

Resolving urban canopy flows: Scales, turbulence and boundary conditions in obstacle-resolving numerical models

2021 ◽  
Author(s):  
Benedikt Seitzer ◽  
Bernd Leitl ◽  
Frank Harms
Keyword(s):  
Boundary Layer ◽  
Boundary Conditions ◽  
Atmospheric Boundary Layer ◽  
Similarity Theory ◽  
Urban Canopy ◽  
Large Eddy Simulations ◽  
Roughness Sublayer ◽  
Boundary Layer Meteorol ◽  
Large Eddy ◽  
Near Wall

<p>Large-eddy simulations are increasingly used for studying the atmospheric boundary layer. With increasing computational resources even obstacle-resolving Large-eddy simulations became possible and will be used in urban climate studies more frequently. In these applications, grid sizes are in the order of a few meters. Whereas major urban structures can be resolved in general, details like aerodynamically rough surface structures can not be resolved explicitly. Based on the original fields of application, boundary conditions in Large-eddy simulations were initially formulated for surfaces of homogeneous roughness and for wall-distances much larger than the roughness sublayer height (Hultmark et al., 2013). The height of the roughness sublayer depends on the size of small-scale obstacles present on the surface exposed to the flow (Raupach et al., 1991). Typically, boundary conditions are evaluated between the surface and the first grid level. Thus, grid resolution in obstacle-resolved Large-Eddy simulations should also be a question of scales and therefore has to be chosen carefully (Basu and Lacser, 2017; Maronga et al., 2020). <br />In several wind tunnel experiments presented here, we measured the near-wall influence of differently scaled and shaped objects on a flow and its turbulence characteristics. Experimental setups were replicated numerically using the PALM model (Maronga et al. 2019). In a first, more generic experiment, the flow over horizontally homogeneous surfaces of different roughness was investigated. In a second experiment, the spatial separation of the turbulence scales was investigated in a more complex flow case. These experiments lead to considerations on model grid sizes in urban type Large-eddy simulations. The limitations of interpreting simulation results within the urban canopy layer are highlighted. There is an urgent need to reconsider how near-wall results of urban large-eddy simulations are generated and interpreted in the context of practical applications like flow and transport modelling in urban canopies. <br /><br /><em><strong>References</strong></em><br /><em>Basu, S. and Lacser, A. (2017). A Cautionary Note on the Use of Monin–Obukhov Similarity Theory in Very High-Resolution Large-Eddy Simulations. Boundary-Layer Meteorol, 163(2):351–355.</em></p> <p><em>Hultmark, M., Calaf, M., and Parlange, M. B. (2013). A new wall shearstress model for atmospheric boundary layer simulations. J Atmos Sci,70(11):3460–3470.</em></p> <p><em>Maronga, B., et al. (2020). Overview of the PALM model system 6.0. Geosci Model Dev Discussions, 06(June):1–63.</em></p> <p><em>Maronga, B., Knigge, C., and Raasch, S. (2020). An Improved Surface Boundary Condition for Large-Eddy Simulations Based on Monin–Obukhov Similarity Theory: Evaluation and Consequences forGrid Convergence in Neutral and Stable Conditions. Boundary-Layer Meteorol, 174(2):297–325.</em></p> <p><em>Raupach, M. R., Antonia, R. A., and Rajagopalan, S. (1991). Rough-wall turbulent boundary layers. Appl Mech Rev, 44(1):1–25</em></p>

k ‐ ϵ Model for the Atmospheric Boundary Layer Under Various Thermal Stratifications

2005 ◽  
Vol 127 (4) ◽  
pp. 438-443 ◽  
Author(s):  
Cédric Alinot ◽  
Christian Masson
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Numerical Solutions ◽  
Stokes Equations ◽  
Similarity Theory ◽  
Turbulence Models ◽  
Boussinesq Approximation ◽  
Momentum Equation ◽  
Navier Stokes ◽  
Production Term

This paper presents a numerical method for predicting the atmospheric boundary layer under stable, neutral, or unstable thermal stratifications. The flow field is described by the Reynolds’ averaged Navier-Stokes equations complemented by the k‐ϵ turbulence model. Density variations are introduced into the momentum equation using the Boussinesq approximation, and appropriate buoyancy terms are included in the k and ϵ equations. An original expression for the closure coefficient related to the buoyancy production term is proposed in order to improve the accuracy of the simulations. The resulting mathematical model has been implemented in FLUENT. The results presented in this paper include comparisons with respect to the Monin-Obukhov similarity theory, measurements, and earlier numerical solutions based on k‐ϵ turbulence models available in the literature. It is shown that the proposed version of the k‐ϵ model significantly improves the accuracy of the simulations for the stable atmospheric boundary layer. In neutral and unstable thermal stratifications, it is shown that the version of the k‐ϵ models available in the literature also produce accurate simulations.

scholarly journals The new BELUGA setup for collocated turbulence and radiation measurements using a tethered balloon: first applications in the cloudy Arctic boundary layer

2019 ◽  
Vol 12 (7) ◽  
pp. 4019-4038 ◽  
Author(s):  
Ulrike Egerer ◽  
Matthias Gottschalk ◽  
Holger Siebert ◽  
André Ehrlich ◽  
Manfred Wendisch
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Turbulent Fluxes ◽  
Lower Atmosphere ◽  
The Arctic ◽  
Radiative Cooling ◽  
Illustrative Case ◽  
Tethered Balloon ◽  
Arctic Boundary Layer ◽  
Radiation Measurements

Abstract. The new BELUGA (Balloon-bornE moduLar Utility for profilinG the lower Atmosphere) tethered balloon system is introduced. It combines a set of instruments to measure turbulent and radiative parameters and energy fluxes. BELUGA enables collocated measurements either at a constant altitude or as vertical profiles up to 1.5 km in height. In particular, the instrument payload of BELUGA comprises three modular instrument packages for high-resolution meteorological, wind vector and broadband radiation measurements. Collocated data acquisition allows for estimates of the driving parameters in the energy balance at various heights. Heating rates and net irradiances can be related to turbulent fluxes and local turbulence parameters such as dissipation rates. In this paper the technical setup, the instrument performance, and the measurement strategy of BELUGA are explained. Furthermore, the high vertical resolution due to the slow ascent speed is highlighted as a major advantage of tethered balloon-borne observations. Three illustrative case studies of the first application of BELUGA in the Arctic atmospheric boundary layer are presented. As a first example, measurements of a single-layer stratocumulus are discussed. They show a pronounced cloud top radiative cooling of up to 6 K h−1. To put this into context, a second case elaborates respective measurements with BELUGA in a cloudless situation. In a third example, a multilayer stratocumulus was probed, revealing reduced turbulence and negligible cloud top radiative cooling for the lower cloud layer. In all three cases the net radiative fluxes are much higher than turbulent fluxes. Altogether, BELUGA has proven its robust performance in cloudy conditions of the Arctic atmospheric boundary layer.

Temperature fluctuations in the atmospheric boundary layer

1960 ◽  
Vol 7 (3) ◽  
pp. 375-384 ◽  
Author(s):  
C. H. B. Priestley
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Thermal Stratification ◽  
Similarity Theory ◽  
Temperature Fluctuations ◽  
Vertical Temperature Gradient ◽  
Vertical Temperature ◽  
Systematic Analysis ◽  
Wide Range ◽  
Regression Relations

A systematic analysis is made of published measurements of the magnitude of temperature fluctuations in the atmospheric boundary layer. These cover a wide range of height, wind speed, and thermal stratification. Within appropriate ranges of the variables, there is evidence for the existence of a dominantly forced convection régime, and also one wherein the predictions of the similarity theory of free convection are fairly closely approached. Subject to the limitations set by the recording systems used, regression relations are obtained for the magnitude of the fluctuations in terms of height and vertical temperature gradient or heat flux.

scholarly journals CheapAML: A Simple, Atmospheric Boundary Layer Model for Use in Ocean-Only Model Calculations

2013 ◽  
Vol 141 (2) ◽  
pp. 809-821 ◽  
Author(s):  
Bruno Deremble ◽  
N. Wienders ◽  
W. K. Dewar
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Wind Field ◽  
Turbulent Fluxes ◽  
Test Cases ◽  
Marine Atmospheric Boundary Layer ◽  
Layer Model ◽  
Global Modeling ◽  
Model Calculations ◽  
Radiative Fluxes

Abstract A model of the marine atmospheric boundary layer is developed for ocean-only modeling in order to better represent air–sea exchanges. This model computes the evolution of the atmospheric boundary layer temperature and humidity using a prescribed wind field. These quantities react to the underlying ocean through turbulent and radiative fluxes. With two examples, the authors illustrate that this formulation is accurate for regional and global modeling purposes and that turbulent fluxes are well reproduced in test cases when compared to reanalysis products. The model builds upon and is an extension of Seager et al.

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