Interaction between the orography-induced gravity wave drag and boundary layer processes in a global atmospheric model

Whole-atmosphere general circulation model captures many aspects of mesoscale gravity wave structures—down to the tens of kilometers—and resulting temperatures and tides.

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Sensitivity and feedback of wind-farm-induced gravity waves

Journal of Fluid Mechanics ◽

10.1017/jfm.2018.969 ◽

2019 ◽

Vol 862 ◽

pp. 990-1028 ◽

Cited By ~ 1

Author(s):

Dries Allaerts ◽

Johan Meyers

Keyword(s):

Boundary Layer ◽

Froude Number ◽

Gravity Wave ◽

Gravity Waves ◽

Wind Farm ◽

Wind Farms ◽

Wave Excitation ◽

Free Atmosphere ◽

Induced Gravity ◽

Wave Induced

Flow blockage by large wind farms leads to an upward displacement of the boundary layer, which may excite atmospheric gravity waves in the free atmosphere and on the interface between the boundary layer and the free atmosphere. In the current study, we assess the sensitivity of wind-farm gravity-wave excitation to important dimensionless groups and investigate the feedback of gravity-wave-induced pressure fields to wind-farm energy extraction. The sensitivity analysis is performed using a fast boundary-layer model that is developed to this end. It is based on a three-layer representation of the atmosphere in an idealised barotropic environment, and is coupled with an analytical wake model to account for turbine wake interactions. We first validate the model in two-dimensional mode with data from previous large-eddy simulations of ‘infinitely’ wide wind farms, and then use the model to investigate the sensitivity of wind-farm-induced gravity waves to atmospheric state and wind-farm configuration. We find that the inversion layer induces flow physics similar to shallow-water flow and that the corresponding Froude number plays a crucial role. Gravity-wave excitation is maximal at a critical Froude number equal to one, but the feedback on energy extraction is highest when the Froude number is slightly below one due to a trade-off between amplitude and upstream impact of gravity waves. The effect of surface friction and internal gravity waves is to reduce the flow perturbation and the related power loss by dissipating or dispersing perturbation energy. With respect to the wind-farm configuration, we find that gravity-wave-induced power loss increases with wind-farm size and turbine height. Moreover, we find that gravity-wave effects are small for very wide or very long wind farms and attain a maximum at a width-to-depth ratio of approximately $3/2$.

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Impact of orographically induced gravity-wave drag in the GLA GCM

Quarterly Journal of the Royal Meteorological Society ◽

10.1002/qj.49712253206 ◽

1996 ◽

Vol 122 (532) ◽

pp. 903-927 ◽

Cited By ~ 23

Author(s):

Jiayu Zhou ◽

Y. C. Sud ◽

K.-M. Lau

Keyword(s):

Gravity Wave ◽

Wave Drag ◽

Induced Gravity

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Gravity-Wave Drag in the Stable Boundary Layer Over Moderate Terrain

Boundary-Layer Meteorology ◽

10.1007/s10546-018-00422-3 ◽

2019 ◽

Vol 171 (2) ◽

pp. 175-189

Author(s):

A. Lapworth ◽

S. R. Osborne

Keyword(s):

Boundary Layer ◽

Gravity Wave ◽

Stable Boundary Layer ◽

Wave Drag ◽

Stable Boundary

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Tropical Cyclones in Rotating Radiative–Convective Equilibrium with Coupled SST

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-16-0195.1 ◽

2017 ◽

Vol 74 (3) ◽

pp. 879-892 ◽

Cited By ~ 9

Author(s):

Wenyu Zhou ◽

Isaac M. Held ◽

Stephen T. Garner

Keyword(s):

Boundary Layer ◽

Angular Momentum ◽

Tropical Cyclones ◽

Atmospheric Model ◽

Ocean Model ◽

Sea Surface ◽

Global Atmospheric Model ◽

Small Depth ◽

Ocean Layer ◽

Slab Ocean

Abstract Tropical cyclones are studied under the idealized framework of rotating radiative–convective equilibrium, achieved in a large doubly periodic f plane by coupling the column physics of a global atmospheric model to rotating hydrostatic dynamics. Unlike previous studies that prescribe uniform sea surface temperature (SST) over the domain, SSTs are now predicted by coupling the atmosphere to a simple slab ocean model. With coupling, SSTs under the eyewall region of tropical cyclones (TCs) become cooler than the environment. However, the domain still fills up with multiple long-lived TCs in all cases examined, including at the limit of the very small depth of the slab. The cooling of SSTs under the eyewall increases as the depth of the slab ocean layer decreases but levels off at roughly 6.5 K as the depth approaches zero. At the eyewall, the storm interior is decoupled from the cooler surface and moist entropy is no longer well mixed along the angular momentum surface in the boundary layer. TC intensity is reduced from the potential intensity computed without the cooling, but the intensity reduction is smaller than that estimated by a potential intensity taking into account the cooling and assuming that moist entropy is well mixed along angular momentum surfaces within the atmospheric boundary layer.

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Sensitivity of the Brewer–Dobson Circulation and Polar Vortex Variability to Parameterized Nonorographic Gravity Wave Drag in a High-Resolution Atmospheric Model

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-17-0304.1 ◽

2018 ◽

Vol 75 (5) ◽

pp. 1525-1543 ◽

Cited By ~ 9

Author(s):

I. Polichtchouk ◽

T. G. Shepherd ◽

R. J. Hogan ◽

P. Bechtold

Keyword(s):

High Resolution ◽

Gravity Wave ◽

Climate Models ◽

Atmospheric Model ◽

Wave Drag ◽

Life Cycles ◽

Late Winter ◽

Polar Cap ◽

The Impact ◽

Temporal Offset

The role of parameterized nonorographic gravity wave drag (NOGWD) and its seasonal interaction with the resolved wave drag in the stratosphere has been extensively studied in low-resolution (coarser than 1.9° × 2.5°) climate models but is comparatively unexplored in higher-resolution models. Using the European Centre for Medium-Range Weather Forecasts Integrated Forecast System at 0.7° × 0.7° resolution, the wave drivers of the Brewer–Dobson circulation are diagnosed and the circulation sensitivity to the NOGW launch flux is explored. NOGWs are found to account for nearly 20% of the lower-stratospheric Southern Hemisphere (SH) polar cap downwelling and for less than 10% of the lower-stratospheric tropical upwelling and Northern Hemisphere (NH) polar cap downwelling. Despite these relatively small numbers, there are complex interactions between NOGWD and resolved wave drag, in both polar regions. Seasonal cycle analysis reveals a temporal offset in the resolved and parameterized wave interaction: the NOGWD response to altered source fluxes is largest in midwinter, while the resolved wave response is largest in the late winter and spring. This temporal offset is especially prominent in the SH. The impact of NOGWD on sudden stratospheric warming (SSW) life cycles and the final warming date in the SH is also investigated. An increase in NOGWD leads to an increase in SSW frequency, reduction in amplitude and persistence, and an earlier recovery of the stratopause following an SSW event. The SH final warming date is also brought forward when NOGWD is increased. Thus, NOGWD is still found to be a very important parameterization for stratospheric dynamics even in a high-resolution atmospheric model.

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