Turbulence Characteristics of the Stable Boundary Layer Over a Mid-Latitude Glacier. Part I: A Combination of Katabatic and Large-Scale Forcing

Smeets, C. J. P. P.; Duynkerke, Peter G.; Vugts, H. F.

doi:10.1023/a:1000860406093

Cited by 78 publications

(79 citation statements)

References 36 publications

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“…1) is valid close to the surface floor so that d can be neglected. Similarity of wind profiles over smooth and sloping ice or snow surfaces is verified by many field experiments within at least several metres above the surface provided that atmospheric stability effects are minimal (e.g., Munro and Davies 1978;Forrer and Rotach 1997;Meesters et al 1997;Smeets et al 1998). …”

Section: A Smooth Ice Surfacementioning

confidence: 58%

Temporal and Spatial Variations of the Aerodynamic Roughness Length in the Ablation Zone of the Greenland Ice Sheet

Smeets

Broeke

2008

Boundary-Layer Meteorol

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130

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To understand the response of the Greenland ice sheet to climate change the so-called ablation zone is of particular importance, since it accommodates the yearly net surface ice loss. In numerical models and for data analysis, the bulk aerodynamic method is often used to calculate the turbulent surface fluxes, for which the aerodynamic roughness length (z 0 ) is a key parameter. We present, for the first time, spatial and temporal variations of z 0 in the ablation area of the Greenland ice sheet using year-round data from three automatic weather stations and one eddy-correlation mast. The temporal variation of z 0 is found to be very high in the lower ablation area (factor 500) with, at the end of the summer melt, a maximum in spatial variation for the whole ablation area of a factor 1000. The variation in time matches the onset of the accumulation and ablation season as recovered by sonic height rangers. During winter, snow accumulation and redistribution by snow drift lead to a uniform value of z 0 ≈ 10 −4 m throughout the ablation area. At the beginning of summer, snow melt uncovers ice hummocks and z 0 quickly increases well above 10 −2 m in the lower ablation area. At the end of summer melt, hummocky ice dominates the surface with z 0 > 5 × 10 −3 m up to 60 km from the ice edge. At the same time, the area close to the equilibrium line (about 90 km from the ice edge) remains very smooth with z 0 = 10 −5 m. At the beginning of winter, we observed that single snow events have the potential to lower z 0 for a very rough ice surface by a factor of 20 to 50. The total surface drag of the abundant small-scale ice hummocks apparently dominates over the less frequent large domes and deep gullies. The latter results are verified by studying the individual drag contributions of hummocks and domes with a drag partition model.

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Section: A Smooth Ice Surfacementioning

confidence: 58%

Temporal and Spatial Variations of the Aerodynamic Roughness Length in the Ablation Zone of the Greenland Ice Sheet

Smeets

Broeke

2008

Boundary-Layer Meteorol

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130

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“…In addition, the spectrum of u-and T-components showed a spectral gap (nz=U < 0:003) for case A and C. We think that a low frequency perturbation induced the gap in the normalized spectra. In the study by Smeets (1998) over the ablation area of Pasterze glacier in Austria, they suggest that the reason for the perturbation is that a significant part of the sensible heat flux is transported at low frequencies over the ablation area. In this study, further work is required to verify such a hypothesis.…”

Section: Resultsmentioning

confidence: 99%

“…Third, the slope of normalized spectra of u and v wind speed components was À2=3 in the inertial sub-range and agrees with Kaimal and Finnigan (1994), but the w spectra do not show such feature and they do not show the k À1 behavior. For comparison with atmospheric spectra, Taylor's hypothesis (Taylor 1938) is employed, i.e., (it is assumed that k ¼ 2pn=U) in mid frequencies (0:05 < nz=U < 1) as in Smeets (1998) and Hőg-strő m et al (1990).…”

Section: Resultsmentioning

confidence: 99%

“…A large number of data sets have been obtained, providing insight into altitudinal gradients of meteorological quantities. Smeets (1998) believed that there were strong low frequency perturbations in the stable boundary layer. These appeared to have a large influence on the variances of wind speed (except for the vertical component) and temperature.…”

Section: Introductionmentioning

confidence: 99%

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The Turbulence Characteristics of the Atmospheric Surface Layer on the North Slope of Mt. Everest Region in the Spring of 2005

Zhong

2012

Journal of the Meteorological Society of Japan

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Turbulence measurements at 3 m performed at the base camp of Mt. Everest during the spring of 2005 were used to study the atmospheric turbulent characteristics under conditions of down-slope ambient wind (katabatic wind). The cases where large-scale forcing resulted in a down-slope ambient wind were considered. Firstly, the normalized standard deviations of wind speed (u and v components) were larger than those reported in the literature. Then the (co)spectral characteristics of turbulence under near neutral stratification were described depending on the prevailing wind; case A-southerly with wind speed larger than 6 m s À1 during daytime, case B-southerly with wind speed less than 6 m s À1 and case C-northerly wind. The analysis of the averaged spectra and co-spectra revealed that low frequency perturbations had a large influence on the variance of u and w wind components, and also altered the co-spectra of momentum and sensible heat flux under near neutral stratification. The features of spectral shape and power were di¤erent from the previous ones under ideal flat and homogeneous conditions. The possible cause of these features is due to strong down-valley flow induced by (normal) glacier wind.

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“…Andreas (2002) tested (6.6) with data from the literature, but these data were collected over snowcovered ground and glaciers. Likewise, Smeets et al (1998) and Denby and Snellen (2002) tested the z T prediction from (6.6) with data collected over Austrian and Icelandic glaciers, respectively, and found good agreement. In another glacier study using data from Greenland and Iceland, Smeets and Van den Broeke (2008) found (6.6) to represent their z T and z Q data well for 5 < R * < 60 but not as well for larger roughness Reynolds numbers.…”

Section: Finding the Scalar Roughness Lengthsmentioning

confidence: 88%

Parametrizing turbulent exchange over summer sea ice and the marginal ice zone

Andreas

Horst

Grachev

et al. 2010

Q.J.R. Meteorol. Soc.

157

188

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The surface of the Arctic Ocean in summer is a mix of sea ice and water in both leads and melt ponds. Here we use data collected at multiple sites during the year-long experiment to study the Surface Heat Budget of the Arctic Ocean (SHEBA) to develop a bulk turbulent flux algorithm for predicting the surface fluxes of momentum and sensible and latent heat over the Arctic Ocean during summer from readily measured or modelled quantities. The distinctive aerodynamic feature of summer sea ice is that the leads and melt ponds create vertical ice faces that the wind can push against; momentum transfer to the surface is thus enhanced through form drag. In effect, summer sea ice behaves aerodynamically like the marginal ice zone, which is another surface that consists of sea ice and water. In our bulk flux algorithm, we therefore combine our SHEBA measurements of the neutral-stability drag coefficient at a reference height of 10 m, C DN10 , with similar measurements from marginal ice zones that have been reported in the literature to create a unified parametrization for C DN10 for summer sea ice and for any marginal ice zone. This parametrization predicts C DN10 from a second-order polynomial in ice concentration. Our bulk flux algorithm also includes expressions for the roughness lengths for temperature and humidity, introduces new profile stratification corrections for stable stratification, and effectively eliminates the singularities that often occur in iterative flux algorithms for very light winds. In summary, this new algorithm seems capable of estimating the friction velocity u

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Turbulence Characteristics of the Stable Boundary Layer Over a Mid-Latitude Glacier. Part I: A Combination of Katabatic and Large-Scale Forcing

Cited by 78 publications

References 36 publications

Temporal and Spatial Variations of the Aerodynamic Roughness Length in the Ablation Zone of the Greenland Ice Sheet

Temporal and Spatial Variations of the Aerodynamic Roughness Length in the Ablation Zone of the Greenland Ice Sheet

The Turbulence Characteristics of the Atmospheric Surface Layer on the North Slope of Mt. Everest Region in the Spring of 2005

Parametrizing turbulent exchange over summer sea ice and the marginal ice zone

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