Analysis of meteorological data and the surface energy balance of McCall Glacier, Alaska, USA

Klok, E. J.; Nolan, M.; Broeke, M. R. van den

doi:10.3189/172756505781829241

Cited by 62 publications

(75 citation statements)

References 35 publications

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“…The performance of these instruments has been described in association with measurements on glaciers around the world (e.g. Georges and Kaser, 2002;Oerlemans and Klok, 2002;Hardy et al, 2003;Klok et al, 2005;. Longwave radiation fluxes are also a measure of glacier (radiative) surface temperature, based on the Stefan-Boltzmann law ( .…”

Section: Automated Measurementsmentioning

confidence: 99%

Mass balance of a slope glacier on Kilimanjaro and its sensitivity to climate

Mölg

Cullen

Hardy

et al. 2007

Intl Journal of Climatology

141

229

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Meteorological and glaciological measurements obtained at 5873 m a.s.l. on Kersten Glacier, a slope glacier on the southern flanks of Kilimanjaro, are used to run a physically-based mass balance model for the period February 2005 to January 2006. This shows that net shortwave radiation is the most variable energy flux at the glacier-atmosphere interface, governed by surface albedo. The majority of the mass loss (∼65%) is due to sublimation (direct conversion of snow/ice to water vapour), with melting of secondary importance. Sensitivity experiments reveal that glacier mass balance is 2-4 times more sensitive to a 20% precipitation change than to a 1°C air temperature change. These figures also hold when the model is run with input data representative of a longer term mean period. Results suggest that a regional-scale moisture projection for the 21st century is crucial to a physically-based prediction of glacier retention on Africa's highest mountain.

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Section: Automated Measurementsmentioning

confidence: 99%

Mass balance of a slope glacier on Kilimanjaro and its sensitivity to climate

Mölg

Cullen

Hardy

et al. 2007

Intl Journal of Climatology

141

229

View full text Add to dashboard Cite

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“…During these snowfall events, K↓ was estimated from α and K↑. α was calculated using an accumulated albedo approach (van den Broeke et al, 2004;Klok et al, 2005), where a mean α (constant value) was calculated using the ratio of the sum of all K↑ to the sum of all K↓ over a daily period. L↓ was parameterized during snowfall events by developing a relationship between L↓ with T and e for unaffected days using a quadratic polynomial regression (Mölg et al, 2008).…”

Section: Aws Data Treatmentmentioning

confidence: 99%

Atmospheric controls on summer ablation over Brewster Glacier, New Zealand

Gillett

Cullen

2010

Intl Journal of Climatology

107

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Micrometeorological data collected from an automatic weather station over a total of 85 days during the summer of 2007/2008 in the ablation zone (1770 m a.s.l.) of the Brewster Glacier, New Zealand, were used to determine the main atmospheric processes controlling the magnitude and variability of daily ablation. During the field season, ablation was measured and modelled using an energy balance model (EBM) and a degree-day model (DDM). Calculation of the energy balance over the glacier using the EBM revealed that net radiation provided the largest source of energy for ablation (52%). The turbulent sensible heat flux was the next largest energy source (25%), followed by the turbulent latent heat flux (20%) and the rain heat flux (3%). While daily measured and modelled (EBM) ablation were both equal to approximately 40 mm w.e. d −1 , the EBM was used to demonstrate that rates were highly variable, ranging from less than 10 mm w.e. d accounted for almost 25% of total ablation, despite such events occurring on only 11 of the 85 days monitored. The contribution of the individual terms of the energy balance to observed air temperature is complex on Brewster Glacier, leading to a larger uncertainty in DDM ablation estimates (under prediction of total ablation by 11%). Advection of warm and moisture-laden air over Brewster Glacier, which is not uncommon given its close proximity to the ocean, is not well accounted for by the DDM. This is because the turbulent latent heat flux and the rain heat flux are poorly correlated to air temperature but are, nonetheless, important sources of energy during large ablation events.

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“…When the atmospheric stability is considered in the bulk method, two approaches are commonly used: (a) one that accounts for stability through the bulk Richardson number (Ri b ) (e.g., Wagnon et al, 2003;Mölg et al, 2008;Anderson et al, 2010;Gillett and Cullen, 2011) and (b) another that uses a M-O stability parameter z L (e.g., Braithwaite, 1995;Klok et al, 2005;Hulth et al, 2010). In both approaches, the stability corrections are empirical functions often derived from field studies on a flat and vegetated terrain.…”

Section: Introductionmentioning

confidence: 99%

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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Analysis of meteorological data and the surface energy balance of McCall Glacier, Alaska, USA

Cited by 62 publications

References 35 publications

Mass balance of a slope glacier on Kilimanjaro and its sensitivity to climate

Mass balance of a slope glacier on Kilimanjaro and its sensitivity to climate

Atmospheric controls on summer ablation over Brewster Glacier, New Zealand

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

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