Glacio-Meteorological Investigations On Vatnajökull, Iceland, Summer 1996: An Overview

Oerlemans, J.; Björnsson, Helgi; Kühn, Michael; Obleitner, Friedrich; Pálsson, Finnur; Smeets, C. J. P. P.; Vugts, H. F.; Wolde, Jan De

doi:10.1023/a:1001856114941

Cited by 89 publications

(72 citation statements)

References 9 publications

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“…The identified prevailing katabatic periods (Fig. 3) overlap with clear-sky conditions and with relatively high near-surface air temperatures (T z t ), as is commonly expected for katabatic flows at glacier surfaces (e.g., Oerlemans et al, 1999).…”

Section: Estimates Of the Roughness Lengthssupporting

confidence: 55%

Evaluation of different methods to model near-surface turbulent fluxes for a mountain glacier in the Cariboo Mountains, BC, Canada

et al. 2017

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Abstract. As part of surface energy balance models used to simulate glacier melting, choosing parameterizations to adequately estimate turbulent heat fluxes is extremely challenging. This study aims to evaluate a set of four aerodynamic bulk methods (labeled as C methods), commonly used to estimate turbulent heat fluxes for a sloped glacier surface, and two less commonly used bulk methods developed from katabatic flow models. The C methods differ in their parameterizations of the bulk exchange coefficient that relates the fluxes to the near-surface measurements of mean wind speed, air temperature, and humidity. The methods' performance in simulating 30 min sensible-and latent-heat fluxes is evaluated against the measured fluxes from an open-path eddycovariance (OPEC) method. The evaluation is performed at a point scale of a mountain glacier, using one-level meteorological and OPEC observations from multi-day periods in the 2010 and 2012 summer seasons. The analysis of the two independent seasons yielded the same key findings, which include the following: first, the bulk method, with or without the commonly used Monin-Obukhov (M-O) stability functions, overestimates the turbulent heat fluxes over the observational period, mainly due to a substantial overestimation of the friction velocity. This overestimation is most pronounced during the katabatic flow conditions, corroborating the previous findings that the M-O theory works poorly in the presence of a low wind speed maximum. Second, the method based on a katabatic flow model (labeled as the K Int method) outperforms any C method in simulating the friction velocity; however, the C methods outperform the K Int method in simulating the sensible-heat fluxes. Third, the best overall performance is given by a hybrid method, which combines the K Int approach with the C method; i.e., it parameterizes eddy viscosity differently than eddy diffusivity. An error analysis reveals that the uncertainties in the measured meteorological variables and the roughness lengths produce errors in the modeled fluxes that are smaller than the differences between the modeled and observed fluxes. This implies that further advances will require improvement to model theory rather than better measurements of input variables. Further data from different glaciers are needed to investigate any universality of these findings.

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Section: Estimates Of the Roughness Lengthssupporting

confidence: 55%

Evaluation of different methods to model near-surface turbulent fluxes for a mountain glacier in the Cariboo Mountains, BC, Canada

et al. 2017

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“…The campaign is described in detail in Oerlemans et al (1999). During the campaign several weather stations were located both on and off the ice.…”

Section: Observationsmentioning

confidence: 99%

“…The near-surface data presented here are hourly averages from the ∼9 m wind mast at station A4 (see Oerlemans et al 1999) at the lower part of Breidamerkurjökull (see Fig. 1).…”

Section: Observationsmentioning

confidence: 99%

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Describing surface fluxes in katabatic flow on Breidamerkurjökull, Iceland

Parmhed

Oerlemans

Grisogono

2004

Quart J Royal Meteoro Soc

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SUMMARYFor very stable boundary layers there is no well-accepted theory today. In this study, an improved Prandtl model with varying diffusivity is applied to less than ideal conditions for pure katabatic flow pertaining to very stable boundary layers. We find that the improved Prandtl model adequately describes the usual and persistent katabatic glacier wind on Breidamerkurjökull. This is true even for flows with very different heights and strengths of the jet. A theoretical estimate of the katabatic jet height, based on temperature deficit and lapse rate, is verified. The calculated surface fluxes compare well with the measured turbulence parameters. A possible reason for the robustness of the katabatic jet (and other low-level jets) is given in terms of the Scorer parameter.

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“…The existence of such winds at the edge of glaciers is known and their diurnal and seasonal cycle has been described for locations, such as the Hintereisferner in the Alps (Obleitner 1994). Extensive observations and modelling efforts have been carried out of katabatic winds over the Breiðamerkurjökull outlet from Vatnajökull glacier in SE-Iceland (Oerlemans et al 1999;Parmhed et al 2004;Söderberg and Parmhed 2006). The experiment showed the katabatic winds to be very persistent over the glacier outlet during summertime, with maximum wind speed typically at few tens of meters above the ground or even lower.…”

Section: Introductionmentioning

confidence: 99%

FLOHOF 2007: an overview of the mesoscale meteorological field campaign at Hofsjökull, Central Iceland

Reuder

Ablinger²,

Ágústsson

et al. 2011

Meteorol Atmos Phys

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Glacio-Meteorological Investigations On Vatnajökull, Iceland, Summer 1996: An Overview

Cited by 89 publications

References 9 publications

Evaluation of different methods to model near-surface turbulent fluxes for a mountain glacier in the Cariboo Mountains, BC, Canada

Evaluation of different methods to model near-surface turbulent fluxes for a mountain glacier in the Cariboo Mountains, BC, Canada

Describing surface fluxes in katabatic flow on Breidamerkurjökull, Iceland

FLOHOF 2007: an overview of the mesoscale meteorological field campaign at Hofsjökull, Central Iceland

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