Spectral Measurements in a Disturbed Boundary Layer over Snow

Andreas, Edgar L.

doi:10.1175/1520-0469(1987)044<1912:smiadb>2.0.co;2

Cited by 42 publications

(19 citation statements)

References 61 publications

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“…Both velocity power spectra were more energetic at low frequencies than are shown by the Kaimal curves, an effect that was particularly evident in the vertical velocity spectra, especially during periods of max flood tide. This same behavior has been observed in the MBBLs [e.g., Scully et al , 2011; Soulsby , 1977] and in many studies in the ABL over various terrains and containing inhomogeneous boundary conditions [e.g., Al‐Jiboori et al , 2001; Andreas , 1987; Högström et al , 1982; Li et al , 2007; McNaughton and Laubach , 2000; Roth et al , 1989; Smeets et al , 1998; Zhang et al , 2010]. Taken collectively, these results suggest that something affects the large‐scale turbulent structures in many natural flows.…”

Section: Discussionsupporting

confidence: 85%

Similarity scaling of turbulence spectra and cospectra in a shallow tidal flow

Walter¹,

Nidzieko²,

Monismith³

2011

J. Geophys. Res.

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[1] Measured turbulence power spectra, cospectra, and ogive curves from a shallow tidal flow were scaled using Monin-Obukhov similarity theory to test the applicability to a generic tidal flow of universal curves found from a uniform, neutrally stable atmospheric boundary layer (ABL). While curves from individual 10 min data bursts deviate significantly from similarity theory, averages over large numbers of sufficiently energetic bursts follow the general shape. However, there are several differences: (1) Variance in the measured curves was shifted toward higher frequencies, (2) at low frequencies, velocity spectra were significantly more energetic than theory while cospectra were weaker, and (3) spectral ratios of momentum flux normalized by turbulent kinetic energy (TKE) indicate decreased fluxes and/or elevated TKE levels. Several features of the turbulence structure may explain these differences. First, turbulent dissipation exceeded production, indicating nonequilibrium turbulence, possibly from advection of TKE. Indeed, using the production rate rather than dissipation markedly improves agreement in the inertial subrange. Second, spectral lag of the largest eddies due to inhomogeneous boundary conditions and decaying turbulence could explain spectral deviations from theory at low frequencies. Finally, since the largest eddies dominate momentum transfer, the consequence of the cospectra difference is that calculated ogive curves produced smaller total momentum fluxes compared to theory, partly because of countergradient fluxes. While ABL similarity scaling applied to marine bottom boundary layers (MBBLs) will produce curves with the general shape of the universal curves, care should be taken in determining details of turbulent energy and stress estimates, particularly in shallow and inhomogeneous MBBLs.

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Section: Discussionsupporting

confidence: 85%

Similarity scaling of turbulence spectra and cospectra in a shallow tidal flow

Walter¹,

Nidzieko²,

Monismith³

2011

J. Geophys. Res.

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“…At temperatures near the freezing point, the flux of latent heat could be important for the energy balance. For these conditions, Hicks and Martin (1972) temperatures, E0 plays only an unimportant role (Andreas, 1987;Weller, 1980;Holmgren, 1971). Latent heat fluxes up to 70 W me2 shown by Rusin (1961) for the Antarctic research station 'Mirny' seem to be unrealistically high.…”

Section: Discussionmentioning

confidence: 99%

Surface energy balance, parameterizations of boundary-layer heights and the application of resistance laws near an Antarctic Ice Shelf front

Heinemann

Rose

1990

Boundary-Layer Meteorol

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A study of the surface energy balance with turbulent fluxes obtained by the Monin-Obukhov similarity theory and a comparison with results for resistance laws are presented for the strong baroclinic conditions in the vicinity of the Filchner/Ronne Ice Shelf front. The data are taken from a field experiment in the Antarctic summer season 1983/84. For the first time in the coastal Antarctic region, this data set comprises synchronous energy balance measurements over the polynya and the ice shelf together with soundings of the boundary layer, yielding vertical profiles of the wind velocity and temperature over the ice shelf, at the ice shelf front and over the polynya.Over the ice shelf. the radiation balance is the largest component of the energy fluxes and is mainly compensated by the subsurface energy flux and the turbulent heat flux in the daily mean. Over the polynya, turbulent fluxes of sensible and latent heat lead to large energy losses of the water surface in the night-time and in situations of very low air temperatures.Different parameterizations for boundary-layer height are compared using tethered sonde and energy balance measurements. With the height of the inversion base over the polynya and the height of the critical bulk Richardson number over the ice shelf, external parameters for the application of resistance laws were determined. The comparison of turbulent surface fluxes obtained by the energy balance measurements and by the resistance laws shows good agreement for the convective conditions over the polynya. For the stably stratified boundary layer over the ice shelf with small amounts of the turbulent heat flux. the deviation is large ior the case of a cold air outflow with a superposed inertial oscillation.

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“…In complex terrain, several studies have shown that atmospheric flow interactions with the orography can generate such features and they may reach the surface and enhance turbulent mixing. In such a case, mixing may not scale with local flow characteristics (Andreas, 1987;Smeets et al, 1999;Poulos et al, 2007;Helgason and Pomeroy, 2012). Near the surface, these eddies would be horizontally deformed due to its blocking effect and to the large shear in the surface layer (Högström et al, 2002): they would disturb the surface layer by inducing large horizontal velocity fluctuations, while vertical velocity would be less influenced.…”

Section: Surface Turbulence Characterisationmentioning

confidence: 99%

Surface-layer turbulence, energy balance and links to atmospheric circulations over a mountain glacier in the French Alps

et al. 2017

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Abstract. Over Saint-Sorlin Glacier in the French Alps (45 • N, 6.1 • E; ∼ 3 km 2 ) in summer, we study the atmospheric surface-layer dynamics, turbulent fluxes, their uncertainties and their impact on surface energy balance (SEB) melt estimates. Results are classified with regard to largescale forcing. We use high-frequency eddy-covariance data and mean air-temperature and wind-speed vertical profiles, collected in 2006 and 2009 in the glacier's atmospheric surface layer. We evaluate the turbulent fluxes with the eddycovariance (sonic) and the profile method, and random errors and parametric uncertainties are evaluated by including different stability corrections and assuming different values for surface roughness lengths. For weak synoptic forcing, local thermal effects dominate the wind circulation. On the glacier, weak katabatic flows with a wind-speed maximum at low height (2-3 m) are detected 71 % of the time and are generally associated with small turbulent kinetic energy (TKE) and small net turbulent fluxes. Radiative fluxes dominate the SEB. When the large-scale forcing is strong, the wind in the valley aligns with the glacier flow, intense downslope flows are observed, no wind-speed maximum is visible below 5 m, and TKE and net turbulent fluxes are often intense. The net turbulent fluxes contribute significantly to the SEB. The surface-layer turbulence production is probably not at equilibrium with dissipation because of interactions of largescale orographic disturbances with the flow when the forcing is strong or low-frequency oscillations of the katabatic flow when the forcing is weak. In weak forcing when TKE is low, all turbulent fluxes calculation methods provide similar fluxes. In strong forcing when TKE is large, the choice of roughness lengths impacts strongly the net turbulent fluxes from the profile method fluxes and their uncertainties. However, the uncertainty on the total SEB remains too high with regard to the net observed melt to be able to recommend one turbulent flux calculation method over another.

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Spectral Measurements in a Disturbed Boundary Layer over Snow

Cited by 42 publications

References 61 publications

Similarity scaling of turbulence spectra and cospectra in a shallow tidal flow

Similarity scaling of turbulence spectra and cospectra in a shallow tidal flow

Surface energy balance, parameterizations of boundary-layer heights and the application of resistance laws near an Antarctic Ice Shelf front

Surface-layer turbulence, energy balance and links to atmospheric circulations over a mountain glacier in the French Alps

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