scholarly journals A two Turbulence Kinetic Energy model as a scale‐adaptive approach to modeling the planetary boundary layer

2016 ◽  
Vol 8 (1) ◽  
pp. 224-243 ◽  
Author(s):  
Ritthik Bhattacharya ◽  
Bjorn Stevens
Keyword(s):  
Boundary Layer ◽  
Kinetic Energy ◽  
Planetary Boundary Layer ◽  
Energy Model ◽  
Turbulence Kinetic Energy ◽  
Adaptive Approach

scholarly journals Improved Length Scales for Turbulence Kinetic Energy–Based Planetary Boundary Layer Scheme for the Convective Atmospheric Boundary Layer

2020 ◽  
Vol 77 (7) ◽  
pp. 2605-2626 ◽  
Author(s):  
Bowen Zhou ◽  
Yuhuan Li ◽  
Kefeng Zhu
Keyword(s):  
Boundary Layer ◽  
Kinetic Energy ◽  
Atmospheric Boundary Layer ◽  
Planetary Boundary Layer ◽  
Turbulent Mixing ◽  
Turbulence Kinetic Energy ◽  
Convective Boundary ◽  
Stability Range ◽  
Length Scales ◽  
Pbl Scheme

AbstractBased on a priori analysis of large-eddy simulations (LESs) of the convective atmospheric boundary layer, improved turbulent mixing and dissipation length scales are proposed for a turbulence kinetic energy (TKE)-based planetary boundary layer (PBL) scheme. The turbulent mixing length incorporates surface similarity and TKE constraints in the surface layer, and makes adjustments for lateral entrainment effects in the mixed layer. The dissipation length is constructed based on balanced TKE budgets accounting for shear, buoyancy, and turbulent mixing. A nongradient term is added to the TKE flux to correct for nonlocal turbulent mixing of TKE. The improved length scales are implemented into a PBL scheme, and are tested with idealized single-column convective boundary layer (CBL) cases. Results exhibit robust applicability across a broad CBL stability range, and are in good agreement with LES benchmark simulations. It is then implemented into a community atmospheric model and further evaluated with 3D real-case simulations. Results of the new scheme are of comparable quality to three other well-established PBL schemes. Comparisons between simulated and radiosonde-observed profiles show favorable performance of the new scheme on a clear day.

scholarly journals Evaluation of turbulence measurement techniques from a single Doppler lidar

2017 ◽  
Vol 10 (8) ◽  
pp. 3021-3039 ◽  
Author(s):  
Timothy A. Bonin ◽  
Aditya Choukulkar ◽  
W. Alan Brewer ◽  
Scott P. Sandberg ◽  
Ann M. Weickmann ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Kinetic Energy ◽  
Planetary Boundary Layer ◽  
Turbulence Intensity ◽  
Measurement Techniques ◽  
Sonic Anemometer ◽  
Shear Velocity ◽  
Turbulence Kinetic Energy ◽  
Doppler Lidar ◽  
Turbulence Measurement

Abstract. Measurements of turbulence are essential to understand and quantify the transport and dispersal of heat, moisture, momentum, and trace gases within the planetary boundary layer (PBL). Through the years, various techniques to measure turbulence using Doppler lidar observations have been proposed. However, the accuracy of these measurements has rarely been validated against trusted in situ instrumentation. Herein, data from the eXperimental Planetary boundary layer Instrumentation Assessment (XPIA) are used to verify Doppler lidar turbulence profiles through comparison with sonic anemometer measurements. For 17 days at the end of the experiment, a single scanning Doppler lidar continuously cycled through different turbulence measurement strategies: velocity–azimuth display (VAD), six-beam scans, and range–height indicators (RHIs) with a vertical stare.Measurements of turbulence kinetic energy (TKE), turbulence intensity, and stress velocity from these techniques are compared with sonic anemometer measurements at six heights on a 300 m tower. The six-beam technique is found to generally measure turbulence kinetic energy and turbulence intensity the most accurately at all heights (r2  ≈  0.78), showing little bias in its observations (slope of  ≈  0. 95). Turbulence measurements from the velocity–azimuth display method tended to be biased low near the surface, as large eddies were not captured by the scan. None of the methods evaluated were able to consistently accurately measure the shear velocity (r2 =  0.15–0.17). Each of the scanning strategies assessed had its own strengths and limitations that need to be considered when selecting the method used in future experiments.

scholarly journals Evaluation of Turbulence Measurement Techniques from a Single Doppler Lidar

2017 ◽  
Author(s):  
Timothy A. Bonin ◽  
Aditya Choukulkar ◽  
W. Alan Brewer ◽  
Scott P. Sandberg ◽  
Ann M. Weickmann ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Kinetic Energy ◽  
Planetary Boundary Layer ◽  
Turbulence Intensity ◽  
Measurement Techniques ◽  
Sonic Anemometer ◽  
Shear Velocity ◽  
Turbulence Kinetic Energy ◽  
Doppler Lidar ◽  
Turbulence Measurement

Abstract. Measurements of turbulence are essential to understand and quantify the transport and dispersal of heat, moisture, momentum, and trace gases within the planetary boundary layer. Through the years, various techniques to measure turbulence using Doppler lidar observations have been proposed. However, the accuracy of these measurements has rarely been validated against trusted in situ instrumentation. Herein, data from the eXperimental Planetary boundary layer Instrumentation Assessment (XPIA) are used to verify Doppler lidar turbulence profiles through comparison with sonic anemometer measurements. For 17 days at the end of the experiment, a single scanning Doppler lidar continuously cycled through different turbulence measurement strategies: velocity azimuth display, six-beam, and range height indicators with a vertical stare. Measurements of turbulence kinetic energy, turbulence intensity, and shear velocity from these techniques are compared with sonic anemometer measurements at six heights on a 300-m tower. The six-beam technique is found to generally measure turbulence kinetic energy and turbulence intensity the most accurately at all heights, showing little bias in its observations. Turbulence measurements from the velocity azimuth display method tended to biased low near the surface, as large eddies were not captured by the scan. None of the methods evaluated were able to consistently accurately measure the shear velocity. Each of the scanning strategies assessed had its own strengths and limitations that need to be considered when selecting the method used in future experiments.

The Martian Planetary Boundary Layer: Turbulent kinetic energy and fundamental similarity scales

2013 ◽  
Vol 47 (6) ◽  
pp. 446-453 ◽  
Author(s):  
G. M. Martínez ◽  
F. Valero ◽  
L. Vázquez ◽  
H. M. Elliott
Keyword(s):  
Boundary Layer ◽  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Planetary Boundary Layer

scholarly journals Turbulence Adjustment and Scaling in an Offshore Convective Internal Boundary Layer: A CASPER Case Study

2020 ◽  
Vol 77 (5) ◽  
pp. 1661-1681
Author(s):  
Qingfang Jiang ◽  
Qing Wang ◽  
Shouping Wang ◽  
Saša Gaberšek
Keyword(s):  
Boundary Layer ◽  
Surface Layer ◽  
Kinetic Energy ◽  
Wind Shear ◽  
Vertical Wind Shear ◽  
Internal Boundary Layer ◽  
Turbulence Kinetic Energy ◽  
Internal Boundary ◽  
Field Observations ◽  
The Mean

Abstract The characteristics of a convective internal boundary layer (CIBL) documented offshore during the East Coast phase of the Coupled Air–Sea Processes and Electromagnetic Ducting Research (CASPER-EAST) field campaign has been examined using field observations, a coupled mesoscale model (i.e., Navy’s COAMPS) simulation, and a couple of surface-layer-resolving large-eddy simulations (LESs). The Lagrangian modeling approach has been adopted with the LES domain being advected from a cool and rough land surface to a warmer and smoother sea surface by the mean offshore winds in the CIBL. The surface fluxes from the LES control run are in reasonable agreement with field observations, and the general CIBL characteristics are consistent with previous studies. According to the LESs, in the nearshore adjustment zone (i.e., fetch < 8 km), the low-level winds and surface friction velocity increase rapidly, and the mean wind profile and vertical velocity skewness in the surface layer deviate substantially from the Monin–Obukhov similarity theory (MOST) scaling. Farther offshore, the nondimensional vertical wind shear and scalar gradients and higher-order moments are consistent with the MOST scaling. An elevated turbulent layer is present immediately below the CIBL top, associated with the vertical wind shear across the CIBL top inversion. Episodic shear instability events occur with a time scale between 10 and 30 min, leading to the formation of elevated maxima in turbulence kinetic energy and momentum fluxes. During these events, the turbulence kinetic energy production exceeds the dissipation, suggesting that the CIBL remains in nonequilibrium.

Derivation of Turbulent Kinetic Energy from a First-Order Nonlocal Planetary Boundary Layer Parameterization

2013 ◽  
Vol 70 (6) ◽  
pp. 1795-1805 ◽  
Author(s):  
Hyeyum Hailey Shin ◽  
Song-You Hong ◽  
Yign Noh ◽  
Jimy Dudhia
Keyword(s):  
Boundary Layer ◽  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Planetary Boundary Layer ◽  
Water Cycle ◽  
Convective Boundary ◽  
First Order ◽  
Eddy Simulation ◽  
Pbl Parameterization ◽  
Planetary Boundary Layer Parameterization

Abstract Turbulent kinetic energy (TKE) is derived from a first-order planetary boundary layer (PBL) parameterization for convective boundary layers: the nonlocal K-profile Yonsei University (YSU) PBL. A parameterization for the TKE equation is developed to calculate TKE based on meteorological profiles given by the YSU PBL model. For this purpose buoyancy- and shear-generation terms are formulated consistently with the YSU scheme—that is, the combination of local, nonlocal, and explicit entrainment fluxes. The vertical transport term is also formulated in a similar fashion. A length scale consistent with the K profile is suggested for parameterization of dissipation. Single-column model (SCM) simulations are conducted for a period in the second Global Energy and Water Cycle Experiment (GEWEX) Atmospheric Boundary Layer Study (GABLS2) intercomparison case. Results from the SCM simulations are compared with large-eddy simulation (LES) results. The daytime evolution of the vertical structure of TKE matches well with mixed-layer development. The TKE profile is shaped like a typical vertical velocity (w) variance, and its maximum is comparable to that from the LES. By varying the dissipation length from −23% to +13% the TKE maximum is changed from about −15% to +7%. After normalization, the change does not exceed the variability among previous studies. The location of TKE maximum is too low without the effects of the nonlocal TKE transport.

Invented Forces in Supercell Models

2021 ◽  
Author(s):  
Robert Davies-Jones
Keyword(s):  
Boundary Layer ◽  
Kinetic Energy ◽  
Planetary Boundary Layer ◽  
Degrees Of Freedom ◽  
Wind Profile ◽  
Equation Of Motion ◽  
Force Balance ◽  
Frictional Loss ◽  
Hydrostatic Equation ◽  
Wind Profiles

AbstractThis paper examines methods used in supercell models to maintain a steady, sheared, horizontally uniform environment with a three-force balance in the planetary boundary layer (PBL) and a two-force balance above it. Steady environments are maintained while ignoring the thermal-wind balance that permits large shear above the PBL. The Taylor-Proudman theorem indicates that wind profiles above the PBL must be unidirectional for balanced environments. In principle, supercell models that do not accommodate thermal advection should not support balanced steady environments with veering horizontally uniform winds.Recent methods add a permanent, pervasive, horizontal external force that varies only with height. By adding two more degrees of freedom, this force circumvents the Taylor-Proudman theorem and enables a static, horizontally uniform environment for any wind profile. It succeeds by adding spurious energy in lieu of flow towards low pressure to offset frictional loss of kinetic energy. However, the artificial force has downsides. It decouples the environmental horizontal equation of motion from the hydrostatic equation and the thermodynamics from the dynamics. It cancels environmental friction and the part of the Coriolis force that acts on the environmental wind. Within the storm, its curl can speciously generate significant horizontal vorticity near the ground. Inaccuracies arise in circulations around material circuits because of modifications by the artificial force and resulting miscalculations of parcel trajectories. Doubt is cast on conclusions about tornadogenesis drawn from recent simulations that contain an invented force.

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