Snowmelt Evolution Mapping Using an Energy Balance Approach over an Alpine Terrain

Mittaz, Catherine; Imhof, Markus; Hoelzle, Martin; Haeberli, Wilfried

doi:10.2307/1552484

Cited by 27 publications

(20 citation statements)

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“…The second line consists of the estimates when all stations are fitted simultaneously, while the first indicates the values estimated by Pirazzini et al (2000). and Oerlemans, 2002;Mittaz et al, 2002;Machguth et al, 2008). Konzelmann et al (1994) is preferred over the Brutsaert (1975) parameterization due to the additive constant representing the clear-sky emissivity of a dry atmosphere to include the effect of greenhouse gases.…”

Section: Parameter Estimation and Validation Of The Clear-sky Ldrmentioning

confidence: 99%

Uncertainties of parameterized surface downward clear-sky shortwave and all-sky longwave radiation.

2012

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Abstract.As many environmental models rely on simulating the energy balance at the Earth's surface based on parameterized radiative fluxes, knowledge of the inherent model uncertainties is important. In this study we evaluate one parameterization of clear-sky direct, diffuse and global shortwave downward radiation (SDR) and diverse parameterizations of clear-sky and all-sky longwave downward radiation (LDR). In a first step, SDR is estimated based on measured input variables and estimated atmospheric parameters for hourly time steps during the years 1996 to 2008. Model behaviour is validated using the high quality measurements of six Alpine Surface Radiation Budget (ASRB) stations in Switzerland covering different elevations, and measurements of the Swiss Alpine Climate Radiation Monitoring network (SACRaM) in Payerne. In a next step, twelve clear-sky LDR parameterizations are calibrated using the ASRB measurements. One of the best performing parameterizations is elected to estimate all-sky LDR, where cloud transmissivity is estimated using measured and modeled global SDR during daytime. In a last step, the performance of several interpolation methods is evaluated to determine the cloud transmissivity in the night.We show that clear-sky direct, diffuse and global SDR is adequately represented by the model when using measurements of the atmospheric parameters precipitable water and aerosol content at Payerne. If the atmospheric parameters are estimated and used as a fix value, the relative mean bias deviance (MBD) and the relative root mean squared deviance (RMSD) of the clear-sky global SDR scatter between between −2 and 5 %, and 7 and 13 % within the six locations. The small errors in clear-sky global SDR can be attributed to compensating effects of modeled direct and diffuse SDR since an overestimation of aerosol content in the atmosphere results in underestimating the direct, but overestimating the diffuse SDR. Calibration of LDR parameterizations to local conditions reduces MBD and RMSD strongly compared to using the published values of the parameters, resulting in relative MBD and RMSD of less than 5 % respectively 10 % for the best parameterizations. The best results to estimate cloud transmissivity during nighttime were obtained by linearly interpolating the average of the cloud transmissivity of the four hours of the preceeding afternoon and the following morning.Model uncertainty can be caused by different errors such as code implementation, errors in input data and in estimated parameters, etc. The influence of the latter (errors in input data and model parameter uncertainty) on model outputs is determined using Monte Carlo. Model uncertainty is provided as the relative standard deviation σ rel of the simulated frequency distributions of the model outputs. An optimistic estimate of the relative uncertainty σ rel resulted in 10 % for the clear-sky direct, 30 % for diffuse, 3 % for global SDR, and 3 % for the fitted all-sky LDR.

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Section: Parameter Estimation and Validation Of The Clear-sky Ldrmentioning

confidence: 99%

Uncertainties of parameterized surface downward clear-sky shortwave and all-sky longwave radiation.

2012

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“…Since the first investigation by IMHOF (1996), extensive permafrost research has taken place on Schilthorn (e.g. HAUCK, 2002;HILBICH et al, 2008;IMHOF et al, 2000;MITTAZ et al, 2002;NOETZLI et al, 2008;VON-DER MÜHLL et al, 2000), making it one of the most intensively investigated permafrost sites in the European Alps. In 1998 the first of three boreholes (14 m deep, followed by two 100 m deep boreholes in 2000) has been drilled on its northern flank at 2900 m asl.…”

Section: Field Sitementioning

confidence: 99%

Influence of atmospheric forcing parameters on modelled mountain permafrost evolution

Engelhardt¹,

Hauck²,

Salzmann³

2010

metz

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To evaluate the sensitivity of mountain permafrost to atmospheric forcing, the dominant meteorological variables such as temperature, precipitation and timing and duration of snow cover have to be considered. Simulations with a one-dimensional coupled heat and mass transfer model (CoupModel) are used to investigate the interactions between the atmosphere and the ground focusing on ground temperature evolution and the temporal variability of the depth of the unfrozen top layer in summer (active layer depth). Idealised and observed atmospheric forcing data sets are used to determine the meteorological conditions, which show the largest impact on the permafrost regime. Borehole temperature and energy balance data from the permafrost station Schilthorn (2900 m asl, Berner Oberland) are used for verification. The results for the Schilthorn site show the largest impact due to summer temperatures changes during the snow free period and to a lesser extent winter precipitation which influence the duration of the snow cover. Similarly important is the timing of the first snow event in autumn which leads to a sufficiently large snow cover to isolate the ground from atmospheric forcing. Simulations with different data sets from Regional Climate Model (RCM) simulations derived from an ensemble of models and scenarios show that the differences in changes of active layer depth between different RCMs are on the same order than between different scenarios. ZusammenfassungUm die Empfindlichkeit von Gebirgspermafrost auf atmosphärischen Einfluss zu untersuchen, müssen die bestimmenden meteorologischen Größen wie Temperatur, Niederschlag, Zeitpunkt und Dauer der Schneebedeckung berücksichtigt werden. Simulationen mit einem eindimensionalen gekoppelten Wärme-und Massentransportmodell (CoupModel) werden verwendet, um die Wechselwirkung zwischen der Atmosphäre und dem Boden zu ermitteln, wobei der Schwerpunkt auf die Bodentemperaturentwicklung und die zeitlichen Schwankungen der ungefrorenen obersten Schicht im Sommer (Auftauschicht) gelegt wird. Idealisierte und beobachtete Daten von atmosphärischen Antriebsgrößen werden verwendet, um die meteorologische Bedingungen zu bestimmen, die den größten Einfluss auf den Permafrost aufweisen. Bohrlochtemperaturdaten und Energiebilanzdaten der Permafroststation Schilthorn (2900 mü. NHN, Berner Oberland) werden zu Kontrollzwecken verwendet. Die Ergebnisse für das Schilthorn zeigen die größte Einwirkung aufgrund von Anderungen der Sommertemperatur während der schneefreien Zeit und zu einem geringeren Ausmaß durch Winterniederschlag, welcher die Zeit der Schneebedeckung beeinflusst. Vonähnlicher Bedeutung ist der Zeitpunkt des ersten Schneefalls im Herbst, der zu einer ausreichend hohen Schneebedeckung führt, um den Boden von atmosphärischem Einfluss zu isolieren. Simulationen mit verschiedenen Zeitreihen regionaler Klimamodelle (RCM), abgeleitet aus einem Ensemble von Modellen und Szenarien, zeigen, dass die Unterschiede derÄnderungen der Auftauschicht aus den Ergebnissen der verschieden...

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“…These data were used to verify an energy-balance model [Gruber et al, 2004] simulating daily surface temperatures based on meteorological observations from the standard Swiss observational network operated by MeteoSwiss. The model is based on the algorithms used in PermEbal [Stocker-Mittaz et al, 2002;Mittaz et al, 2002] and simulates the one-dimensional energy balance at the rock surface as well as the subsurface heat conduction using daily time steps. After calculation of the short-wave net radiation and the long-wave irradiance, the turbulent heat flux and upwelling long-wave radiation are parameterized using an estimated surface temperature.…”

Section: Introductionmentioning

confidence: 99%

Permafrost thaw and destabilization of Alpine rock walls in the hot summer of 2003

Gruber

Hoelzle

Haeberli

2004

Geophysical Research Letters

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353

299

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[1] Exceptional rockfall occurred throughout the Alps during the unusually hot summer of 2003. It is likely related to the fast thermal reaction of the subsurface of steep rock slopes and a corresponding destabilization of ice-filled discontinuities. This suggests that rockfall may be a direct and unexpectedly fast impact of climate change. Based upon our measurements in Alpine rock faces, we present model simulations illustrating the distribution and degradation of permafrost where the summer of 2003 has resulted in extreme thaw. We argue that hotter summers predicted by climate models for the coming decades will result in reduced stability of many alpine rock walls.

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Snowmelt Evolution Mapping Using an Energy Balance Approach over an Alpine Terrain

Cited by 27 publications

References 0 publications

Uncertainties of parameterized surface downward clear-sky shortwave and all-sky longwave radiation.

Uncertainties of parameterized surface downward clear-sky shortwave and all-sky longwave radiation.

Influence of atmospheric forcing parameters on modelled mountain permafrost evolution

Permafrost thaw and destabilization of Alpine rock walls in the hot summer of 2003

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