scholarly journals Reconnaissance Study of glacier energy balance in North Greenland, 1993–94

1998 ◽  
Vol 44 (147) ◽  
pp. 239-247 ◽  
Author(s):  
Roger J. Braithwaite ◽  
Thomas Konzelmann ◽  
Christoph Marty ◽  
Ole B. Olesen
Keyword(s):  
Energy Balance ◽  
Field Experiments ◽  
Longwave Radiation ◽  
Heat Fluxes ◽  
Shortwave Radiation ◽  
Balance Model ◽  
Conductive Heat ◽  
Glacier Surface ◽  
West Greenland ◽  
North Greenland

AbstractReconnaissance energy-balance studies were made for the first time at two sites in North Greenland to compare with conditions in West Greenland. The field experiments were planned to save weight because it is expensive to operate in North Greenland. The larger energy components (incoming radiation and ablation) were measured for 55 days altogether, and the smaller components were evaluated by indirect methods, e.g. turbulent fluxes are calculated from air temperature, humidity and wind speed, to save the weight of instruments. The energy-balance model is “tuned" by choosing surface roughness and albedo to reduce the mean error between measured ablation and modelled daily melting. The error standard deviation for ablation is only ± 5 kg m−2d−1’, which is much lower than found in West Greenland, due to better instruments and modelling in the present study. Net radiation is the main energy source for melting in North Greenland but ablation is relatively low because sublimation and conductive-heat fluxes use energy that would otherwise be available for melting. There is a strong diurnal variation in ablation, mainly forced by variations in shortwave radiation and reinforced by nocturnal cooling of the ice surface by outgoing longwave radiation and sublimation. The model frequently predicts a frozen glacier surface at night even when air temperatures are positive.

scholarly journals Reconnaissance Study of glacier energy balance in North Greenland, 1993–94

1998 ◽  
Vol 44 (147) ◽  
pp. 239-247 ◽  
Author(s):  
Roger J. Braithwaite ◽  
Thomas Konzelmann ◽  
Christoph Marty ◽  
Ole B. Olesen
Keyword(s):  
Energy Balance ◽  
Field Experiments ◽  
Longwave Radiation ◽  
Heat Fluxes ◽  
Shortwave Radiation ◽  
Balance Model ◽  
Conductive Heat ◽  
Glacier Surface ◽  
West Greenland ◽  
North Greenland

AbstractReconnaissance energy-balance studies were made for the first time at two sites in North Greenland to compare with conditions in West Greenland. The field experiments were planned to save weight because it is expensive to operate in North Greenland. The larger energy components (incoming radiation and ablation) were measured for 55 days altogether, and the smaller components were evaluated by indirect methods, e.g. turbulent fluxes are calculated from air temperature, humidity and wind speed, to save the weight of instruments. The energy-balance model is “tuned" by choosing surface roughness and albedo to reduce the mean error between measured ablation and modelled daily melting. The error standard deviation for ablation is only ± 5 kg m −2 d−1’, which is much lower than found in West Greenland, due to better instruments and modelling in the present study. Net radiation is the main energy source for melting in North Greenland but ablation is relatively low because sublimation and conductive-heat fluxes use energy that would otherwise be available for melting. There is a strong diurnal variation in ablation, mainly forced by variations in shortwave radiation and reinforced by nocturnal cooling of the ice surface by outgoing longwave radiation and sublimation. The model frequently predicts a frozen glacier surface at night even when air temperatures are positive.

scholarly journals The role of radiation penetration in the energy budget of the snowpack at Summit, Greenland

2009 ◽  
Vol 3 (2) ◽  
pp. 155-165 ◽  
Author(s):  
P. Kuipers Munneke ◽  
M. R. van den Broeke ◽  
C. H. Reijmer ◽  
M. M. Helsen ◽  
W. Boot ◽  
...  
Keyword(s):  
Energy Balance ◽  
Model Simulation ◽  
Longwave Radiation ◽  
Heat Fluxes ◽  
Heat Sinks ◽  
Shortwave Radiation ◽  
Balance Model ◽  
Radiative Transfer Model ◽  
Transfer Model

Abstract. Measurements of the summer surface energy balance at Summit, Greenland, are presented (8 June–20 July 2007). These measurements serve as input to an energy balance model that searches for a surface temperature for which closure of all energy terms is achieved. A good agreement between observed and modelled surface temperatures was found, with an average difference of 0.45°C and an RMSE of 0.85°C. It turns out that penetration of shortwave radiation into the snowpack plays a small but important role in correctly simulating snow temperatures. After 42 days, snow temperatures in the first meter are 3.6–4.0°C higher compared to a model simulation without radiation penetration. Sensitivity experiments show that these results cannot be reproduced by tuning the heat conduction process alone, by varying snow density or snow diffusivity. We compared the two-stream radiation penetration calculations with a sophisticated radiative transfer model and discuss the differences. The average diurnal cycle shows that net shortwave radiation is the largest energy source (diurnal average of +61 W m−2), net longwave radiation the largest energy sink (−42 W m−2). On average, subsurface heat flux, sensible and latent heat fluxes are the remaining, small heat sinks (−5, −5 and −7 W m−2, respectively), although these are more important on a subdaily timescale.

scholarly journals The surface energy balance of Austre Lovénbreen, Svalbard, during the ablation period in 2014

2021 ◽  
Vol 40 ◽  
Author(s):  
Xiaowei Zou ◽  
Minghu Ding ◽  
Weijun Sun ◽  
Diyi Yang ◽  
Weigang Liu ◽  
...  
Keyword(s):  
Energy Balance ◽  
Surface Energy ◽  
Surface Albedo ◽  
Surface Energy Balance ◽  
Meteorological Data ◽  
Longwave Radiation ◽  
Heat Sinks ◽  
Shortwave Radiation ◽  
Balance Model ◽  
Glacier Surface

The ability to simulate the surface energy balance is key to studying land–atmosphere interactions; however, it remains a weakness in Arctic polar sciences. Based on the analysis of meteorological data from 1 June to 30 September 2014 from an automatic weather station on the glacier Austre Lovénbreen, near Ny–Ålesund, Svalbard, we established a surface energy balance model to simulate surface melt. The results reveal that the net shortwave radiation accounts for 87% (39 W m–2) of the energy sources, and is controlled by cloud cover and surface albedo. The sensible heat equals 6 W m–2 and is a continuous energy source at the glacier surface. Net longwave radiation and latent heat account for 31% and 5% of heat sinks, respectively. The simulated summer mass balance equals –793 mm w.e., agreeing well with the observation by an ultrasonic ranger.

scholarly journals A 22 month record of surface meteorology and energy balance from the ablation zone of Brewster Glacier, New Zealand

2015 ◽  
Vol 61 (229) ◽  
pp. 931-946 ◽  
Author(s):  
Nicolas J. Cullen ◽  
Jonathan P. Conway
Keyword(s):  
New Zealand ◽  
Energy Balance ◽  
Longwave Radiation ◽  
Heat Fluxes ◽  
Shortwave Radiation ◽  
Ablation Zone ◽  
Glacier Surface ◽  
Freezing Level ◽  
Climate Interactions

AbstractMulti-annual records of glacier surface meteorology and energy balance are necessary to resolve glacier–climate interactions but remain sparse, especially in the Southern Hemisphere. To address this, we present a record from the ablation zone of Brewster Glacier, New Zealand, between October 2010 and September 2012. The mean air temperature was 1.2°C at 1760 m a.s.l., with only a moderate temperature difference between the warmest and coldest months (∼8°C). Long-term annual precipitation was estimated to exceed 6000 mm a−1, with the majority of precipitation falling within a few degrees of the freezing level. The main melt season was between November and March (83% of annual ablation), but melt events occurred during all months. Annually, net radiation was positive (a source of energy) and supplied 64% of the melt energy, driven primarily by net shortwave radiation. Net longwave radiation was often positive during cloudy conditions in summer, demonstrating the radiative importance of clouds during melt. Turbulent sensible and latent heat fluxes were directed towards the surface in the summer months, accounting for just over a third of the energy for melt (34%). The energy gain associated with rainfall was small except during heavy events in summer.

scholarly journals The role of radiation penetration in the energy budget of the snowpack at Summit, Greenland

2009 ◽  
Vol 3 (1) ◽  
pp. 277-306 ◽  
Author(s):  
P. Kuipers Munneke ◽  
M. R. van den Broeke ◽  
C. H. Reijmer ◽  
M. M. Helsen ◽  
W. Boot ◽  
...  
Keyword(s):  
Energy Balance ◽  
Model Simulation ◽  
Longwave Radiation ◽  
Heat Fluxes ◽  
Heat Sinks ◽  
Shortwave Radiation ◽  
Balance Model ◽  
Radiative Transfer Model ◽  
Transfer Model

Abstract. Measurements of the summer surface energy balance at Summit, Greenland, are presented (8 June–20 July 2007). These measurements serve as input to an energy balance model that searches for a surface temperature for which closure of all energy terms is achieved. A good agreement between observed and modeled surface temperatures was found, with an average difference of 0.45°C and an RMSE of 0.85°C. It turns out that penetration of shortwave radiation into the snowpack plays a small but important role in correctly simulating snow temperatures. After 42 days, snow temperatures in the first meter are 3.6–4.0°C higher compared to a model simulation without radiation penetration. Sensitivity experiments show that these results cannot be reproduced by tuning the heat conduction process alone, by varying snow density or snow diffusivity. We compared the two-stream radiation penetration calculations with a sophisticated radiative transfer model and discuss the differences. The average diurnal cycle shows that net shortwave radiation is the largest energy source (+61 W m−2 on average), net longwave radiation the largest energy sink (−42 W m−2). On average, subsurface heat flux, sensible and latent heat fluxes are the remaining, small heat sinks (−5, −5 and −7 W m−2, respectively), although these are more important on a subdaily timescale.

scholarly journals Application of an improved surface energy balance model to two large valley glaciers in the St. Elias Mountains, Yukon

2020 ◽  
pp. 1-16
Author(s):  
Tim Hill ◽  
Christine F. Dow ◽  
Eleanor A. Bash ◽  
Luke Copland
Keyword(s):  
Energy Balance ◽  
Surface Energy ◽  
Surface Energy Balance ◽  
Shortwave Radiation ◽  
Balance Model ◽  
Landsat 8 ◽  
Glacier Surface ◽  
Ice Dynamics ◽  
Surface Melt

Abstract Glacier surficial melt rates are commonly modelled using surface energy balance (SEB) models, with outputs applied to extend point-based mass-balance measurements to regional scales, assess water resource availability, examine supraglacial hydrology and to investigate the relationship between surface melt and ice dynamics. We present an improved SEB model that addresses the primary limitations of existing models by: (1) deriving high-resolution (30 m) surface albedo from Landsat 8 imagery, (2) calculating shadows cast onto the glacier surface by high-relief topography to model incident shortwave radiation, (3) developing an algorithm to map debris sufficiently thick to insulate the glacier surface and (4) presenting a formulation of the SEB model coupled to a subsurface heat conduction model. We drive the model with 6 years of in situ meteorological data from Kaskawulsh Glacier and Nàłùdäy (Lowell) Glacier in the St. Elias Mountains, Yukon, Canada, and validate outputs against in situ measurements. Modelled seasonal melt agrees with observations within 9% across a range of elevations on both glaciers in years with high-quality in situ observations. We recommend applying the model to investigate the impacts of surface melt for individual glaciers when sufficient input data are available.

scholarly journals On the role of subsurface heat conduction in glacier energy-balance modelling

2009 ◽  
Vol 50 (50) ◽  
pp. 16-24 ◽  
Author(s):  
Francesca Pellicciotti ◽  
Marco Carenzo ◽  
Jakob Helbing ◽  
Stefan Rimkus ◽  
Paolo Burlando
Keyword(s):  
Heat Conduction ◽  
Energy Balance ◽  
Shortwave Radiation ◽  
Balance Model ◽  
Glacier Surface ◽  
Central Chile ◽  
Air Temperatures ◽  
Weather Stations ◽  
The Difference

AbstractWe discuss the inclusion of the subsurface heat-conduction flux into the calculation of the energy balance and ablation at the glacier–atmosphere interface. Data from automatic weather stations are used to force an energy-balance model at several locations on alpine glaciers and at one site in the dry Andes of central Chile. The heat-conduction flux is computed using a two-layer scheme, assuming that 36% of the net shortwave radiation is absorbed by the surface layer and that the rest penetrates into the snowpack. We compare simulations conducted with and without subsurface heat flux. Results show that assuming a surface temperature of zero degrees leads to a larger overestimation of melt at the sites in the accumulation area (10.4–13.3%) than in the ablation area (0.5–2.8%), due to lower air temperatures and the presence of snow. The difference between simulations with and without heat conduction is also high at the beginning and end of the ablation season (up to 29% for the first 15 days of the season), when air temperatures are lower and snow covers the glacier surface, while they are of little importance during periods of sustained melt at all the locations investigated.

scholarly journals Thermal resistances in the Everest Area (Nepal Himalaya) derived from satellite imagery using a nonlinear energy balance model

2014 ◽  
Vol 8 (1) ◽  
pp. 887-918 ◽  
Author(s):  
D. R. Rounce ◽  
D. C. McKinney
Keyword(s):  
Energy Balance ◽  
Temperature Gradient ◽  
Satellite Imagery ◽  
Heat Fluxes ◽  
Energy Balance Model ◽  
Shortwave Radiation ◽  
Balance Model ◽  
Turbulent Heat ◽  
Turbulent Heat Fluxes ◽  
Nonlinear Temperature

Abstract. Debris thickness is an important characteristic of many debris-covered glaciers in the Everest region of the Himalayas. The debris thickness controls the melt rates of the glaciers, which has large implications for hydrologic models, the glaciers response to climate change, and the development of glacial lakes. Despite its importance, there is little knowledge of how the debris thickness varies over these glaciers. This paper uses an energy balance model in conjunction with Landsat7 ETM+ satellite imagery to derive thermal resistances, which is the debris thickness divided by the thermal conductivity. The developed model accounts for the nonlinear temperature gradient in the debris cover to derive accurate thermal resistances. Fieldwork performed on Lhotse Shar/Imja glacier in September 2013 was used to validate the satellite-derived thermal resistances. Results indicate that accounting for the nonlinear temperature gradient is crucial. Furthermore, correcting the incoming shortwave radiation term for the effects of topography and including the turbulent heat fluxes is imperative to derive accurate thermal resistances. Since the topographic correction is important, the model will improve with the quality of the DEM. The main limitation of this work is the poor resolution (60 m) of the satellite's thermal band. The derived thermal resistances are accurate at this resolution, but are unable to derive trends related to slope and aspect on a finer scale. Nonetheless, the study finds this model derives accurate thermal resistances on this scale and is transferable to other debris-covered glaciers in the Everest region.

scholarly journals Energy-balance model validation on the top of Kilimanjaro, Tanzania, using eddy covariance data

2007 ◽  
Vol 46 ◽  
pp. 227-233 ◽  
Author(s):  
Nicolas J. Cullen ◽  
Thomas Mölg ◽  
Georg Kaser ◽  
Konrad Steffen ◽  
Douglas R. Hardy
Keyword(s):  
Energy Balance ◽  
Eddy Covariance ◽  
Longwave Radiation ◽  
Heat Fluxes ◽  
Balance Model ◽  
Turbulent Heat ◽  
Turbulent Heat Fluxes ◽  
Roughness Lengths ◽  
Order Of Magnitude ◽  
Important Input

AbstractEddy covariance data collected over a horizontal surface on the largest ice body on Kilimanjaro, Tanzania, over 26–29 July 2005 were used to assess the uncertainty of calculating sublimation with a surface energy balance (SEB) model. Data required for input to the SEB model were obtained from an existing automatic weather station. Surface temperatures that were solved iteratively by the SEB model were used to compute emitted longwave radiation, turbulent heat fluxes using the aerodynamic bulk method and the subsurface heat flux. Roughness lengths for momentum and temperature, which were found to be the most important input parameters controlling the magnitude of modelled (bulk method) turbulent heat fluxes, were obtained using eddy covariance data. The roughness length for momentum was estimated to be 1.7×10–3 m, while the length for temperature was one order of magnitude smaller. Modelled sensible and latent heat fluxes (bulk method) compared well to eddy covariance data, with root-mean-square differences between 3.1 and 4.8 Wm–2 for both turbulent heat fluxes. Modelled sublimation accounted for about 90% of observed ablation, confirming that mass loss by melting is much less important than sublimation on the horizontal surfaces of the remaining plateau glaciers on Kilimanjaro.

scholarly journals Glacier subsurface heat-flux characterizations for energy-balance modelling in the Donjek Range, southwest Yukon, Canada

2011 ◽  
Vol 57 (201) ◽  
pp. 121-133 ◽  
Author(s):  
Brett A. Wheler ◽  
Gwenn E. Flowers
Keyword(s):  
Heat Flux ◽  
Energy Balance ◽  
Surface Temperature ◽  
Energy Balance Equation ◽  
Shortwave Radiation ◽  
Balance Model ◽  
Glacier Surface ◽  
Sophisticated Model ◽  
The Mean ◽  
Polythermal Glacier

AbstractWe apply a point-scale energy-balance model to a small polythermal glacier in the St Elias Mountains of Canada in order to investigate the applicability and limitations of different treatments of the glacier surface temperature and subsurface heat flux. These treatments range in complexity from a multilayer subsurface model that simulates snowpack evolution, to the assumption of a constant glacier surface temperature equal to 0°C. The most sophisticated model includes dry densification of the snowpack, penetration of shortwave radiation into the subsurface, internal melting, refreezing of percolating meltwater and generation of slush layers. Measurements of subsurface temperature and surface lowering are used for model validation, and highlight the importance of including subsurface penetration of shortwave radiation in the model. Using an iterative scheme to solve for the subsurface heat flux as the residual of the energy-balance equation results in an overestimation of total ablation by 18%, while the multilayer subsurface model underestimates ablation by 6%. By comparison, the 0°C surface assumption leads to an overestimation of ablation of 29% in this study where the mean annual air temperature is about −8°C.

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