Relationship between Low-Level Jet Properties and Turbulence Kinetic Energy in the Nocturnal Stable Boundary Layer

Banta, Robert M.; Pichugina, Yelena L.; Newsom, RK

doi:10.1175/1520-0469(2003)060<2549:rbljpa>2.0.co;2

Cited by 132 publications

(208 citation statements)

References 16 publications

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“…Second, buoyant turbulence production (instead of loss) may occur over steep slopes even in statically stable conditions [188,189]. Despite being essentially turbulent, katabatic flows or other flows with a low-level wind maximum do not match the standard ABL structure [185,190,191]. Therefore, the applicability of MOST or of local scaling approaches for katabatic flow has been called into question [192] and is a matter of on-going debate [191].…”

Section: The Stable Boundary Layer Over Slopesmentioning

confidence: 99%

Exchange Processes in the Atmospheric Boundary Layer Over Mountainous Terrain

et al. 2018

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Abstract:The exchange of heat, momentum, and mass in the atmosphere over mountainous terrain is controlled by synoptic-scale dynamics, thermally driven mesoscale circulations, and turbulence. This article reviews the key challenges relevant to the understanding of exchange processes in the mountain boundary layer and outlines possible research priorities for the future. The review describes the limitations of the experimental study of turbulent exchange over complex terrain, the impact of slope and valley breezes on the structure of the convective boundary layer, and the role of intermittent mixing and wave-turbulence interaction in the stable boundary layer. The interplay between exchange processes at different spatial scales is discussed in depth, emphasizing the role of elevated and ground-based stable layers in controlling multi-scale interactions in the atmosphere over and near mountains. Implications of the current understanding of exchange processes over mountains towards the improvement of numerical weather prediction and climate models are discussed, considering in particular the representation of surface boundary conditions, the parameterization of sub-grid-scale exchange, and the development of stochastic perturbation schemes.

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Section: The Stable Boundary Layer Over Slopesmentioning

confidence: 99%

Exchange Processes in the Atmospheric Boundary Layer Over Mountainous Terrain

et al. 2018

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“…The NBL depths are close between 0000 and 0700 LST, but differ significantly between about 2000 and 2400 LST; sunset is at around 1945 LST in July and 1915 LST in August. For these cases, the NBL depths using f = 0.1 and f = 0.05 have been compared to subjective estimates of NBL depths based on the lidar wind-speed profiles (e.g., Banta et al 2003;Pichugina and Banta 2010). Comparing results from all profiles during the study period, the value of f = 0.1 produced a better agreement with the subjectively determined NBL depths; therefore we selected f = 0.1 for this dataset.…”

Section: Defining the Nbl Depth Using Fractional σ 2 Wmentioning

confidence: 99%

Estimate of Boundary-Layer Depth Over Beijing, China, Using Doppler Lidar Data During SURF-2015

Huang

Gao

Miao

et al. 2016

Boundary-Layer Meteorol

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Planetary boundary-layer (PBL) structure was investigated using observations from a Doppler lidar and the 325-m Institute of Atmospheric Physics (IAP) meteorological tower in the centre of Beijing during the summer 2015 Study of Urban-impacts on Rainfall and Fog/haze (SURF-2015) field campaign. Using six fair-weather days of lidar and tower data under clear to cloudy skies, we evaluate the ability of the Doppler lidar to probe the urban boundary-layer structure, and then propose a composite method for estimating the diurnal cycle of the PBL depth using the Doppler lidar. For the convective boundary layer (CBL), a threshold method using vertical velocity variance (σ 2 w > 0.1 m 2 s −2 ) is used, since it provides more reliable CBL depths than a conventional maximum wind-shear method. The nocturnal boundary-layer (NBL) depth is defined as the height at which σ 2 w decreases to 10 % of its near-surface maximum minus a background variance. The PBL depths determined by combining these methods have average values ranging from ≈270 to ≈1500 m for the six days, with the greatest maximum depths associated with clear skies. Release of stored and anthropogenic heat contributes to the maintenance of turbulence until late evening, keeping the NBL near-neutral and deeper at night than would be expected over a natural surface. The NBL typically becomes more shallow with time, but grows in the presence of low-level nocturnal jets. While current results are promising, data over a broader range of conditions are needed to fully develop our PBL-depth algorithms.

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“…Turbulent mixing occurs when Ri is below a critical threshold, typically values smaller than 0.4 (e.g. Banta et al 2003). A long or short-tail function f (Ri) is implemented and artificially increases the vertical mixing in stable boundary layers so that higher nocturnal near-surface winds are simulated than observed (Brown et al 2006(Brown et al , 2008Sandu et al 2013).…”

Section: Stable Boundary Layermentioning

confidence: 99%

A process-based evaluation of dust-emitting winds in the CMIP5 simulation of HadGEM2-ES

et al. 2015

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Medium-Range Weather Forecasts. Compared to ERAInterim, a stronger pressure ridge over northern Africa in winter and the southward displaced heat low in summer result in differences in location and strength of NLLJs. Particularly the larger geostrophic winds associated with the stronger ridge have a strengthening effect on NLLJs over parts of West Africa in winter. Stronger NLLJs in summer may rather result from an artificially increased mixing coefficient under stable stratification that is weaker in HadGEM2-ES. NLLJs in the Bodélé Depression are affected by stronger synoptic-scale pressure gradients in HadGEM2-ES. Wintertime geostrophic winds can even be so strong that the associated vertical wind shear prevents the formation of NLLJs. These results call for further model improvements in the synoptic-scale dynamics and the physical parametrization of the nocturnal stable boundary layer to better represent dust-emitting processes in the atmospheric model. The new approach could be used for identifying systematic behavior in other models with respect to meteorological processes for dust emission. This would help to improve dust emission simulations and contribute to decreasing the currently large uncertainty in climate change projections with respect to dust aerosol.

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Relationship between Low-Level Jet Properties and Turbulence Kinetic Energy in the Nocturnal Stable Boundary Layer

Cited by 132 publications

References 16 publications

Exchange Processes in the Atmospheric Boundary Layer Over Mountainous Terrain

Exchange Processes in the Atmospheric Boundary Layer Over Mountainous Terrain

Estimate of Boundary-Layer Depth Over Beijing, China, Using Doppler Lidar Data During SURF-2015

A process-based evaluation of dust-emitting winds in the CMIP5 simulation of HadGEM2-ES

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