Low-level wind profiles at an Antarctic coastal station

1989 ◽  
Vol 1 (2) ◽  
pp. 169-178 ◽  
Author(s):  
J.C. King
Keyword(s):  
Boundary Layer ◽  
Temperature Profiles ◽  
Pressure Gradients ◽  
Synoptic Scale ◽  
Layer Model ◽  
Coastal Station ◽  
One Dimensional ◽  
Dimensional Boundary ◽  
Sloping Surface ◽  
Wind Profiles

Wind and temperature profiles in the lowest 2000 m of the atmosphere at Halley (75°35′S, 26°50′W) have been analysed. Surface winds blow most frequently from the sector 090° ± 45° but the 2000 m wind direction is much more evenly distributed and appears to be determined by synoptic-scale pressure gradients. A simple one-dimensional boundary layer model, which includes the effects of stably-stratified air overlying a sloping surface, is able to reproduce some of the features of the observed profiles.

Instabilities of the von Kármán Boundary Layer

2015 ◽  
Vol 67 (3) ◽  
Author(s):  
R. J. Lingwood ◽  
P. Henrik Alfredsson
Keyword(s):  
Boundary Layer ◽  
Three Dimensional ◽  
Rotating Disk ◽  
Direct Numerical Simulations ◽  
Layer Model ◽  
Complex Flow ◽  
Von Karman ◽  
Dimensional Boundary ◽  
Flow Configurations ◽  
Von Kármán

Research on the von Kármán boundary layer extends back almost 100 years but remains a topic of active study, which continues to reveal new results; it is only now that fully nonlinear direct numerical simulations (DNS) have been conducted of the flow to compare with theoretical and experimental results. The von Kármán boundary layer, or rotating-disk boundary layer, provides, in some senses, a simple three-dimensional boundary-layer model with which to compare other more complex flow configurations but we will show that in fact the rotating-disk boundary layer itself exhibits a wealth of complex instability behaviors that are not yet fully understood.

scholarly journals Simulating Real Atmospheric Boundary Layers at Gray-Zone Resolutions: How Do Currently Available Turbulence Parameterizations Perform?

Atmosphere ◽  
2020 ◽  
Vol 11 (4) ◽  
pp. 345 ◽  
Author(s):  
Paula Doubrawa ◽  
Domingo Muñoz-Esparza
Keyword(s):  
Boundary Layer ◽  
Turbulent Transport ◽  
Model Performance ◽  
Wrf Model ◽  
Turbulent Energy ◽  
Complex Problem ◽  
Gray Zone ◽  
Horizontal Structure ◽  
One Dimensional ◽  
Dimensional Boundary

Recent computational and modeling advances have led a diverse modeling community to experiment with atmospheric boundary layer (ABL) simulations at subkilometer horizontal scales. Accurately parameterizing turbulence at these scales is a complex problem. The modeling solutions proposed to date are still in the development phase and remain largely unvalidated. This work assesses the performance of methods currently available in the Weather Research and Forecasting (WRF) model to represent ABL turbulence at a gray-zone grid spacing of 333 m. We consider three one-dimensional boundary layer parameterizations (MYNN, YSU and Shin-Hong) and coarse large-eddy simulations (LES). The reference dataset consists of five real-case simulations performed with WRF-LES nested down to 25 m. Results reveal that users should refrain from coarse LES and favor the scale-aware, Shin-Hong parameterization over traditional one-dimensional schemes. Overall, the spread in model performance is large for the cellular convection regime corresponding to the majority of our cases, with coarse LES overestimating turbulent energy across scales and YSU underestimating it and failing to reproduce its horizontal structure. Despite yielding the best results, the Shin-Hong scheme overestimates the effect of grid dependence on turbulent transport, highlighting the outstanding need for improved solutions to seamlessly parameterize turbulence across scales.

Effect of Adverse Pressure Gradients on Turbulent Boundary Layers in Axisymmetric Conduits

1957 ◽  
Vol 24 (2) ◽  
pp. 191-196
Author(s):  
J. M. Robertson ◽  
J. W. Holl
Keyword(s):  
Boundary Layer ◽  
Flow Parameter ◽  
Three Dimensional ◽  
Turbulent Boundary Layers ◽  
Pressure Gradients ◽  
Two Dimensional ◽  
Flow Conditions ◽  
Straight Pipe ◽  
Outer Flow ◽  
Dimensional Boundary

Abstract The development of the three-dimensional boundary layer in a diffuser with several discharge arrangements has been studied for air flow, in continuation of the work of Uram (1). The flow conditions in a diffuser when followed by a straight pipe, an additional length of the diffuser, or a jet, are compared. Extension of the method of analysis developed by Ross for two-dimensional layers is presented. In some cases the use of three-dimensionally defined parameters leads to different results. Ross’s (2) unique outer-flow parameter is found to be no longer satisfactory. Other outer parameters are presented as possible substitutes.

scholarly journals On the Relationship between SST Gradients, Boundary Layer Winds, and Convergence over the Tropical Oceans

2009 ◽  
Vol 22 (15) ◽  
pp. 4182-4196 ◽  
Author(s):  
Larissa E. Back ◽  
Christopher S. Bretherton
Keyword(s):  
Boundary Layer ◽  
Deep Convection ◽  
Force Balance ◽  
Semiempirical Model ◽  
Pressure Gradients ◽  
Surface Winds ◽  
Layer Model ◽  
Zonal Winds ◽  
Tropical Oceans ◽  
The Relationship

Abstract A linear mixed layer model that skillfully reproduces observed surface winds and convergence over the tropical oceans is used to examine the relative influence of boundary layer and free-tropospheric processes on the distribution of climatological surface winds and convergence. The semiempirical model assumes a subcloud-layer momentum force balance between pressure gradients, Coriolis acceleration, linearized friction, and downward momentum mixing, and it utilizes boundary conditions from the 40-yr ECMWF Re-Analysis (ERA-40). Observed pressure gradients are linearly decomposed into boundary layer (defined as the region below 850 hPa) and free-tropospheric components, and the surface winds and convergence associated with these components are computed. Results show that surface zonal winds are predominantly associated with a combination of free-tropospheric pressure gradients and downward momentum mixing, whereas the distribution of convergence is primarily due to boundary layer temperature gradients, which are closely related to SST gradients. The authors conclude that the climatological distribution of boundary layer convergence is primarily a function of the pattern of SST gradients and is better regarded as a cause rather than a consequence of deep convection.

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