Small-scale orographic gravity wave drag in stable boundary layers and its impact on synoptic systems and near-surface meteorology

Abstract This paper uses idealized numerical simulations to investigate the dynamical influences of stable boundary layers on the morphology of supercell thunderstorms, especially the development of low-level rotation. Simulations are initialized in a horizontally homogeneous environment with a surface-based stable layer similar to that found within a nocturnal boundary layer or a mesoscale cold pool. The depth and lapse rate of the imposed stable boundary layer, which together control the convective inhibition (CIN), are varied in a suite of experiments. When compared with a control simulation having little surface-based CIN, each supercell simulated in an environment having a stable boundary layer develops weaker rotation, updrafts, and downdrafts at low levels; in general, low-level vertical vorticity and vertical velocity magnitude decrease as initial CIN increases (changes in CIN are due only to variations in the imposed stable boundary layer). Though the presence of a stable boundary layer decreases low-level updraft strength, all supercells except those initiated over the most stable boundary layers had at least some updraft parcels with near-surface origins. Furthermore, the existence of a stable boundary layer only prohibits downdraft parcels from reaching the lowest grid level in the most stable cases. Trajectory and circulation analyses indicate that weaker near-surface rotation in the stable-layer scenarios is a result of the decreased generation of circulation coupled with decreased convergence of the near-surface circulation by weaker low-level updrafts. These results may also suggest a reason why tornadogenesis is less likely to occur in so-called elevated supercell thunderstorms than in surface-based supercells.

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On the computation of planetary boundary-layer height using the bulk Richardson number method

Geoscientific Model Development ◽

10.5194/gmd-7-2599-2014 ◽

2014 ◽

Vol 7 (6) ◽

pp. 2599-2611 ◽

Cited By ~ 45

Author(s):

Y. Zhang ◽

Z. Gao ◽

D. Li ◽

Y. Li ◽

N. Zhang ◽

...

Keyword(s):

Boundary Layer ◽

Boundary Layers ◽

Planetary Boundary Layer ◽

Richardson Number ◽

Potential Temperature ◽

Bulk Richardson Number ◽

Stable Boundary Layers ◽

Stable Boundary ◽

Field Campaigns ◽

Weakly Stable

Abstract. Experimental data from four field campaigns are used to explore the variability of the bulk Richardson number of the entire planetary boundary layer (PBL), Ribc, which is a key parameter for calculating the PBL height (PBLH) in numerical weather and climate models with the bulk Richardson number method. First, the PBLHs of three different thermally stratified boundary layers (i.e., strongly stable boundary layers, weakly stable boundary layers, and unstable boundary layers) from the four field campaigns are determined using the turbulence method, the potential temperature gradient method, the low-level jet method, and the modified parcel method. Then for each type of boundary layer, an optimal Ribc is obtained through linear fitting and statistical error minimization methods so that the bulk Richardson method with this optimal Ribc yields similar estimates of PBLHs as the methods mentioned above. We find that the optimal Ribc increases as the PBL becomes more unstable: 0.24 for strongly stable boundary layers, 0.31 for weakly stable boundary layers, and 0.39 for unstable boundary layers. Compared with previous schemes that use a single value of Ribc in calculating the PBLH for all types of boundary layers, the new values of Ribc proposed by this study yield more accurate estimates of PBLHs.

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Generalizing ‘z-less’ mixing length for stable boundary layers

Quarterly Journal of the Royal Meteorological Society ◽

10.1002/qj.529 ◽

2010 ◽

Vol 136 (646) ◽

pp. 213-221 ◽

Cited By ~ 24

Author(s):

B. Grisogono

Keyword(s):

Boundary Layers ◽

Mixing Length ◽

Stable Boundary Layers ◽

Stable Boundary

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Turbulence, Radiation and fog in Dutch Stable Boundary Layers

Boundary-Layer Meteorology ◽

10.1023/a:1026441904734 ◽

1999 ◽

Vol 90 (3) ◽

pp. 447-477 ◽

Cited By ~ 99

Author(s):

Peter G. Duynkerke

Keyword(s):

Boundary Layers ◽

Stable Boundary Layers ◽

Stable Boundary

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Large-Eddy Simulation of Stably Stratified Atmospheric Boundary Layer Turbulence: A Scale-Dependent Dynamic Modeling Approach

Journal of the Atmospheric Sciences ◽

10.1175/jas3734.1 ◽

2006 ◽

Vol 63 (8) ◽

pp. 2074-2091 ◽

Cited By ~ 123

Author(s):

Sukanta Basu ◽

Fernando Porté-Agel

Keyword(s):

Boundary Layers ◽

Temperature Fields ◽

Scale Model ◽

Subgrid Scale ◽

Local Scaling ◽

Stable Boundary Layers ◽

Stable Boundary ◽

Boundary Layer Turbulence ◽

Scaling Hypothesis ◽

Large Eddy

Abstract A new tuning-free subgrid-scale model, termed locally averaged scale-dependent dynamic (LASDD) model, is developed and implemented in large-eddy simulations (LES) of stable boundary layers. The new model dynamically computes the Smagorinsky coefficient and the subgrid-scale Prandtl number based on the local dynamics of the resolved velocity and temperature fields. Overall, the agreement between the statistics of the LES-generated turbulence and some well-established empirical formulations and theoretical predictions (e.g., the local scaling hypothesis) is remarkable. Moreover, the simulated statistics obtained with the LASDD model show relatively little resolution dependence for the range of grid sizes considered here. In essence, it is shown here that the new LASDD model is a robust subgrid-scale parameterization for reliable, tuning-free simulations of stable boundary layers, even with relatively coarse resolutions.

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