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Title: A Large-Eddy Simulation Study of Atmospheric Boundary Layer Influence on Stratified Flows over Terrain

In this study, the impact of atmospheric boundary layer (ABL) interactions with large-scale stably stratified flow over an isolated, two-dimensional hill is investigated using turbulence-resolving large-eddy simulations. The onset of internal gravity wave breaking and leeside flow response regimes of trapped lee waves and nonlinear breakdown (or hydraulic-jump-like state) as they depend on the classical inverse Froude number, Fr -1 = Nh/U g, is explored in detail. Here, N is the Brunt–Väisälä frequency, h is the hill height, and U g is the geostrophic wind. The results here demonstrate that the presence of a turbulent ABL influences mountain wave (MW) development in critical aspects, such as dissipation of trapped lee waves and amplified stagnation zone turbulence through Kelvin–Helmholtz instability. It is shown that the nature of interactions between the large-scale flow and the ABL is better characterized by a proposed inverse compensated Froude number, Fr$$-1\atop{c}$$ = N(h - z i)/U g, where z i is the ABL height. In addition, it is found that the onset of the nonlinear-breakdown regime, Fr$$-1\atop{c}$$ ≈ 1.0, is initiated when the vertical wavelength becomes comparable to the sufficiently energetic scales of turbulence in the stagnation zone and ABL, yielding an abrupt change in leeside flow response. Lastly, energy spectra are presented in the context of MW flows, supporting the existence of a clear transition in leeside flow response, and illustrating two distinct energy distribution states for the trapped-lee-wave and the nonlinear-breakdown regimes.
Authors:
 [1] ;  [2] ; ORCiD logo [1] ; ORCiD logo [1] ; ORCiD logo [1] ;  [1]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  2. Research Applications Laboratory, National Center for Atmospheric Research, Boulder, CO (United States)
Publication Date:
Report Number(s):
LA-UR-15-27177
Journal ID: ISSN 0022-4928
Grant/Contract Number:
AC52-06NA25396
Type:
Accepted Manuscript
Journal Name:
Journal of the Atmospheric Sciences
Additional Journal Information:
Journal Volume: 73; Journal Issue: 7; Journal ID: ISSN 0022-4928
Publisher:
American Meteorological Society
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE National Nuclear Security Administration (NNSA)
Country of Publication:
United States
Language:
English
Subject:
97 MATHEMATICS AND COMPUTING; 54 ENVIRONMENTAL SCIENCES; Models and modeling; Large eddy simulations; Applications; Mountain meteorology
OSTI Identifier:
1457262

Sauer, Jeremy A., Munoz-Esparza, Domingo, Canfield, Jesse M., Costigan, Keeley Rochelle, Linn, Rodman Ray, and Kim, Young-Joon. A Large-Eddy Simulation Study of Atmospheric Boundary Layer Influence on Stratified Flows over Terrain. United States: N. p., Web. doi:10.1175/JAS-D-15-0282.1.
Sauer, Jeremy A., Munoz-Esparza, Domingo, Canfield, Jesse M., Costigan, Keeley Rochelle, Linn, Rodman Ray, & Kim, Young-Joon. A Large-Eddy Simulation Study of Atmospheric Boundary Layer Influence on Stratified Flows over Terrain. United States. doi:10.1175/JAS-D-15-0282.1.
Sauer, Jeremy A., Munoz-Esparza, Domingo, Canfield, Jesse M., Costigan, Keeley Rochelle, Linn, Rodman Ray, and Kim, Young-Joon. 2016. "A Large-Eddy Simulation Study of Atmospheric Boundary Layer Influence on Stratified Flows over Terrain". United States. doi:10.1175/JAS-D-15-0282.1. https://www.osti.gov/servlets/purl/1457262.
@article{osti_1457262,
title = {A Large-Eddy Simulation Study of Atmospheric Boundary Layer Influence on Stratified Flows over Terrain},
author = {Sauer, Jeremy A. and Munoz-Esparza, Domingo and Canfield, Jesse M. and Costigan, Keeley Rochelle and Linn, Rodman Ray and Kim, Young-Joon},
abstractNote = {In this study, the impact of atmospheric boundary layer (ABL) interactions with large-scale stably stratified flow over an isolated, two-dimensional hill is investigated using turbulence-resolving large-eddy simulations. The onset of internal gravity wave breaking and leeside flow response regimes of trapped lee waves and nonlinear breakdown (or hydraulic-jump-like state) as they depend on the classical inverse Froude number, Fr-1 = Nh/Ug, is explored in detail. Here, N is the Brunt–Väisälä frequency, h is the hill height, and Ug is the geostrophic wind. The results here demonstrate that the presence of a turbulent ABL influences mountain wave (MW) development in critical aspects, such as dissipation of trapped lee waves and amplified stagnation zone turbulence through Kelvin–Helmholtz instability. It is shown that the nature of interactions between the large-scale flow and the ABL is better characterized by a proposed inverse compensated Froude number, Fr$-1\atop{c}$ = N(h - zi)/Ug, where zi is the ABL height. In addition, it is found that the onset of the nonlinear-breakdown regime, Fr$-1\atop{c}$ ≈ 1.0, is initiated when the vertical wavelength becomes comparable to the sufficiently energetic scales of turbulence in the stagnation zone and ABL, yielding an abrupt change in leeside flow response. Lastly, energy spectra are presented in the context of MW flows, supporting the existence of a clear transition in leeside flow response, and illustrating two distinct energy distribution states for the trapped-lee-wave and the nonlinear-breakdown regimes.},
doi = {10.1175/JAS-D-15-0282.1},
journal = {Journal of the Atmospheric Sciences},
number = 7,
volume = 73,
place = {United States},
year = {2016},
month = {6}
}