scholarly journals A preliminary assessment of glacier melt-model parameter sensitivity and transferability in a dry subarctic environment

2011 ◽  
Vol 5 (4) ◽  
pp. 1011-1028 ◽  
Author(s):  
A. H. MacDougall ◽  
B. A. Wheler ◽  
G. E. Flowers
Keyword(s):  
Energy Balance ◽  
Parameter Sensitivity ◽  
Energy Balance Model ◽  
Balance Model ◽  
Model Parameters ◽  
Temperature Index ◽  
Model Parameter ◽  
Index Model ◽  
Degree Day ◽  
Model Tuning

Abstract. Efforts to project the long-term melt of mountain glaciers and ice-caps require that melt models developed and calibrated for well studied locations be transferable over large regions. Here we assess the sensitivity and transferability of parameters within several commonly used melt models for two proximal sites in a dry subarctic environment of northwestern Canada. The models range in complexity from a classical degree-day model to a simplified energy-balance model. Parameter sensitivity is first evaluated by tuning the melt models to the output of an energy balance model forced with idealized inputs. This exercise allows us to explore parameter sensitivity both to glacier geometric attributes and surface characteristics, as well as to meteorological conditions. We then investigate the effect of model tuning with different statistics, including a weighted coefficient of determination (wR2), the Nash-Sutcliffe efficiency criterion (E), mean absolute error (MAE) and root mean squared error (RMSE). Finally we examine model parameter transferability between two neighbouring glaciers over two melt seasons using mass balance data collected in the St. Elias Mountains of the southwest Yukon. The temperature-index model parameters appear generally sensitive to glacier aspect, mean surface elevation, albedo, wind speed, mean annual temperature and temperature lapse rate. The simplified energy balance model parameters are sensitive primarily to snow albedo. Model tuning with E, MAE and RMSE produces similar, or in some cases identical, parameter values. In twelve tests of spatial and/or temporal parameter transferability, the results with the lowest RMSE values with respect to ablation stake measurements were achieved twice with a classical temperature-index (degree-day) model, three times with a temperature-index model in which the melt parameter is a function of potential radiation, and seven times with a simplified energy-balance model. A full energy-balance model produced better results than the other models in nine of twelve cases, though the tuning of this model differs from that of the others.

scholarly journals Assessment of glacier melt-model transferability: comparison of temperature-index and energy-balance models

2010 ◽  
Vol 4 (4) ◽  
pp. 2143-2167 ◽  
Author(s):  
A. H. MacDougall ◽  
B. A. Wheler ◽  
G. E. Flowers
Keyword(s):  
Energy Balance ◽  
Energy Balance Model ◽  
The Other ◽  
Balance Model ◽  
Simple Relationship ◽  
Temperature Index ◽  
Full Energy ◽  
Model Transferability ◽  
Glacier Melt ◽  
Surface Ablation

Abstract. Transferability of glacier melt models is necessary for reliable projections of melt over large glacierized regions and over long time-scales. The transferability of such models has been examined for individual model types, but inter-comparison has been hindered by the diversity of validation statistics used to quantify transferability. We apply four common types of melt models – the classical degree-day model, an enhanced temperature-index model, a simplified energy-balance model and a full energy-balance model – to two glaciers in the same small mountain range. The transferability of each model is examined in space and over two melt seasons. We find that the full energy balance model is consistently the most transferable, with deviations in estimated glacier-wide surface ablation of ≤ 35% when the model is forced with parameters derived from the other glacier and/or melt season. The other three models have deviations in glacier-wide surface ablation of ≥ 100% under the same forcings. In addition, we find that there is no simple relationship between model complexity and model transferability.

scholarly journals Development of a Mass and Energy Balance Model and Its Application for HBI Charged EAFs

Metals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 311
Author(s):  
Niloofar Arzpeyma ◽  
Rutger Gyllenram ◽  
Pär G. Jönsson
Keyword(s):  
Energy Balance ◽  
Slag Composition ◽  
Electricity Consumption ◽  
Electric Arc ◽  
Energy Balance Model ◽  
Balance Model ◽  
Model Parameters ◽  
Metal Oxidation ◽  
Arc Furnaces ◽  
Hot Briquetted Iron

A static mass and energy balance model combined with a MgO saturation slag model is developed for electric arc furnaces. The model parameters including distribution ratios and dust factors are calibrated for a specific furnace using experimental data. Afterward, the model is applied to study the effect of charging different amounts of hot briquetted iron (HBI) on energy consumption, charged slag former amount, and slag composition. The following results were obtained per each 1% increase of HBI additions: (i) a 0.16 Nm3/t decrease in the amount of injected oxygen for metal oxidation, (ii) a 1.29 kWh/t increase in the electricity consumption, and (iii) a 34 kg increase in the amount of the slag.

scholarly journals Transient Climate Response in a Two-Layer Energy-Balance Model. Part I: Analytical Solution and Parameter Calibration Using CMIP5 AOGCM Experiments

2013 ◽  
Vol 26 (6) ◽  
pp. 1841-1857 ◽  
Author(s):  
O. Geoffroy ◽  
D. Saint-Martin ◽  
D. J. L. Olivié ◽  
A. Voldoire ◽  
G. Bellon ◽  
...  
Keyword(s):  
Thermal Properties ◽  
Energy Balance ◽  
Analytical Solution ◽  
Deep Ocean ◽  
Energy Balance Model ◽  
Balance Model ◽  
Model Parameters ◽  
Climate Change Scenarios ◽  
Ocean Heat Uptake ◽  
Transient Climate Response

Abstract This is the first part of a series of two articles analyzing the global thermal properties of atmosphere–ocean coupled general circulation models (AOGCMs) within the framework of a two-layer energy-balance model (EBM). In this part, the general analytical solution of the system is given and two idealized climate change scenarios, one with a step forcing and one with a linear forcing, are discussed. These solutions give a didactic description of the contributions from the equilibrium response and of the fast and slow transient responses during a climate transition. Based on these analytical solutions, a simple and physically based procedure to calibrate the two-layer model parameters using an AOGCM step-forcing experiment is introduced. Using this procedure, the global thermal properties of 16 AOGCMs participating in phase 5 of the Coupled Model Intercomparison Project (CMIP5) are determined. It is shown that, for a given AOGCM, the EBM tuned with only the abrupt 4×CO2 experiment is able to reproduce with a very good accuracy the temperature evolution in both a step-forcing and a linear-forcing experiment. The role of the upper-ocean and deep-ocean heat uptakes in the fast and slow responses is also discussed. One of the main weaknesses of the simple EBM discussed in this part is its ability to represent the evolution of the top-of-the-atmosphere radiative imbalance in the transient regime. This issue is addressed in Part II by taking into account the efficacy factor of deep-ocean heat uptake.

scholarly journals Assessing the transferability and robustness of an enhanced temperature-index glacier-melt model

2009 ◽  
Vol 55 (190) ◽  
pp. 258-274 ◽  
Author(s):  
Marco Carenzo ◽  
Francesca Pellicciotti ◽  
Stefan Rimkus ◽  
Paolo Burlando
Keyword(s):  
Energy Balance ◽  
Meteorological Conditions ◽  
Shortwave Radiation ◽  
Balance Model ◽  
Model Parameters ◽  
Radiation Factor ◽  
Temperature Index ◽  
Clear Sky ◽  
Few Data ◽  
Parameter Values

AbstractWe investigate the transferability of an enhanced temperature-index melt model that was developed and tested on Haut Glacier d’Arolla, Switzerland, in the 2001 season. The model’s empirical parameters (temperature factor, TF, and shortwave radiation factor, SRF) are recalibrated for: (1) other locations on Haut Glacier d’Arolla; (2) subperiods of distinct meteorological conditions; (3) different years on Haut Glacier d’Arolla; and (4) other glaciers in different years. The model parameters are optimized against simulations of an energy-balance model validated against ablation observations. Results are compared with those obtained with the original parameters. The model works very well when applied to other sites, seasons and glaciers, with the exception of overcast conditions. Differences are due to underestimation of high melt rates. The parameter values are associated with the prevailing energy-balance conditions, showing that high SRF are obtained on clear-sky days, whereas higher TF are typical of locations where glacier winds prevail and turbulent fluxes are high. We also provide a range of parameters clearly associated with the site’s location and its meteorological characteristics that could help to assign parameter values to sites where few data are available.

scholarly journals A distributed temperature-index ice- and snowmelt model including potential direct solar radiation

1999 ◽  
Vol 45 (149) ◽  
pp. 101-111 ◽  
Author(s):  
Regine Hock
Keyword(s):  
Solar Radiation ◽  
Global Radiation ◽  
Model Performance ◽  
Direct Solar Radiation ◽  
Balance Model ◽  
Temperature Index ◽  
Index Model ◽  
Clear Sky ◽  
Degree Day ◽  
Daily Discharge

AbstractHourly melt and discharge of Storglaciären, a small glacier in Sweden, were computed for two melt seasons, applying temperature-index methods to a 30 m resolution grid for the melt component. The classical degree-day method yielded a good simulation of the seasonal patient of discharge, but the pronounced melt-induced daily discharge cycles were not captured. Modelled degree-day factors calculated for every hour and each gridcell from melt obtained from a distributed energy-balance model varied substantially, both diurnally and spatially. A new distributed temperature-index model is suggested, attempting to capture both the pronounced diurnal melt cycles and the spatial variations in melt due to the effects of surrounding topography. This is accomplished by including a radiation index in terms of potential clear-sky direct solar radiation, and thus, without the need for other data besides air temperature. This approach improved considerably the simulation of diurnal discharge fluctuations and yielded a more realistic spatial distribution of melt rates. The incorporation of measured global radiation to account for the reduction in direct solar radiation due to cloudiness did not lead to additional improvement in model performance.

scholarly journals Mass-balance modelling of the Greenland ice sheet: a comparison of an energy-balance and a degree-day model

1996 ◽  
Vol 23 ◽  
pp. 36-45 ◽  
Author(s):  
R. S. W. van de Wal
Keyword(s):  
Energy Balance ◽  
Mass Balance ◽  
Sea Level Rise ◽  
Sea Level ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Energy Balance Model ◽  
Balance Model ◽  
Temperature Perturbation ◽  
Degree Day

A degree-day model and an energy-balance model for the Greenland ice sheet are compared. The two models are compared at a grid with 20 km spacing. Input for both models is elevation, latitude and accumulation. The models calculate the annual ablation over the entire ice sheet. Although on the whole the two models yield similar results, depending on the tuning of the models, regional discrepancies of up to 45% occur, especially for northern Greenland. The performance of the two types of model is evaluated by comparing the model results with the sparsely available (long-term) mass-balance measurements. Results show that the energy-balance model tends to predict a more accurate mass-balance gradient with elevation than does the degree-day model. Since so little is known about the present-day climate of the ice sheet, it is more useful to consider the sensitivity of the ablation to various climate elements than to consider the actual present-day ablation. Results show that for a 1 K temperature perturbation, sea-level rise is 0.31 mm year−1 for the energy-balance model and 0.34 mm year−1 for the degree-day model. After tuning the degree-day model to a value of the ablation, equivalent to the ablation calculated by the energy-balance model, sensitivity of the degree-day model increases to 0.37 mm sea-level change per year. This means that the sensitivity of the degree-day model for a 1 K temperature perturbation is about 20% higher than the sensitivity of the energy-balance model. Another set of experiments shows that the sensitivity of the ablation is dependent on the magnitude of the temperature perturbation for the two models. Both models show an increasing sensitivity per degree for larger perturbations. The increase in the sensitivity is larger for the degree-day model than for the energy-balance model. The differences in the sensitivity are mainly concentrated in the southern parts of the ice sheet. Experiments for the Bellagio temperature scenario. 0.3°C increase in temperature per decade, leads to sea-level rise of 4.4 cm over a period of 100 years for the energy-balance model. The degree-day model predicts for the same forcing a 5.8 cm rise which is about 32% higher than the result of the energy-balance model.

scholarly journals Degree-day factor, energy balance, and the increased melting of the Greenland ice sheet under a warmer climate

1992 ◽  
Vol 155 ◽  
pp. 79-83
Author(s):  
R.J Braithwaite
Keyword(s):  
Energy Balance ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Climatic Conditions ◽  
Energy Balance Model ◽  
Balance Model ◽  
Time And Space ◽  
Degree Day ◽  
Sensitivity Experiments ◽  
Field Samples

Ablation on the Greenland ice Sheet can be calculated either from the degree-day factor or by an energy balance model. Both approaches involve problems. i.e. the degree-day factor varies with time and space while the energy balance model requires data which are often not available. The solution is to understand, and possibly predict variations in degree-day factor. This can be attempted by (1) sensitivity experiments with the energy balance model, and (2) field samples of ablation under widely varying climatic conditions.

scholarly journals Mass-balance modelling of the Greenland ice sheet: a comparison of an energy-balance and a degree-day model

1996 ◽  
Vol 23 ◽  
pp. 36-45 ◽  
Author(s):  
R. S. W. van de Wal
Keyword(s):  
Energy Balance ◽  
Mass Balance ◽  
Sea Level Rise ◽  
Sea Level ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Energy Balance Model ◽  
Balance Model ◽  
Temperature Perturbation ◽  
Degree Day

A degree-day model and an energy-balance model for the Greenland ice sheet are compared. The two models are compared at a grid with 20 km spacing. Input for both models is elevation, latitude and accumulation. The models calculate the annual ablation over the entire ice sheet. Although on the whole the two models yield similar results, depending on the tuning of the models, regional discrepancies of up to 45% occur, especially for northern Greenland. The performance of the two types of model is evaluated by comparing the model results with the sparsely available (long-term) mass-balance measurements. Results show that the energy-balance model tends to predict a more accurate mass-balance gradient with elevation than does the degree-day model.Since so little is known about the present-day climate of the ice sheet, it is more useful to consider the sensitivity of the ablation to various climate elements than to consider the actual present-day ablation. Results show that for a 1 K temperature perturbation, sea-level rise is 0.31 mm year−1 for the energy-balance model and 0.34 mm year−1 for the degree-day model. After tuning the degree-day model to a value of the ablation, equivalent to the ablation calculated by the energy-balance model, sensitivity of the degree-day model increases to 0.37 mm sea-level change per year. This means that the sensitivity of the degree-day model for a 1 K temperature perturbation is about 20% higher than the sensitivity of the energy-balance model. Another set of experiments shows that the sensitivity of the ablation is dependent on the magnitude of the temperature perturbation for the two models. Both models show an increasing sensitivity per degree for larger perturbations. The increase in the sensitivity is larger for the degree-day model than for the energy-balance model. The differences in the sensitivity are mainly concentrated in the southern parts of the ice sheet.Experiments for the Bellagio temperature scenario. 0.3°C increase in temperature per decade, leads to sea-level rise of 4.4 cm over a period of 100 years for the energy-balance model. The degree-day model predicts for the same forcing a 5.8 cm rise which is about 32% higher than the result of the energy-balance model.

scholarly journals A distributed temperature-index ice- and snowmelt model including potential direct solar radiation

1999 ◽  
Vol 45 (149) ◽  
pp. 101-111 ◽  
Author(s):  
Regine Hock
Keyword(s):  
Solar Radiation ◽  
Global Radiation ◽  
Model Performance ◽  
Direct Solar Radiation ◽  
Balance Model ◽  
Temperature Index ◽  
Index Model ◽  
Clear Sky ◽  
Degree Day ◽  
Daily Discharge

AbstractHourly melt and discharge of Storglaciären, a small glacier in Sweden, were computed for two melt seasons, applying temperature-index methods to a 30 m resolution grid for the melt component. The classical degree-day method yielded a good simulation of the seasonal patient of discharge, but the pronounced melt-induced daily discharge cycles were not captured. Modelled degree-day factors calculated for every hour and each gridcell from melt obtained from a distributed energy-balance model varied substantially, both diurnally and spatially. A new distributed temperature-index model is suggested, attempting to capture both the pronounced diurnal melt cycles and the spatial variations in melt due to the effects of surrounding topography. This is accomplished by including a radiation index in terms of potential clear-sky direct solar radiation, and thus, without the need for other data besides air temperature. This approach improved considerably the simulation of diurnal discharge fluctuations and yielded a more realistic spatial distribution of melt rates. The incorporation of measured global radiation to account for the reduction in direct solar radiation due to cloudiness did not lead to additional improvement in model performance.

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