scholarly journals Debris thickness of glaciers in the Everest area (Nepal Himalaya) derived from satellite imagery using a nonlinear energy balance model

2014 ◽  
Vol 8 (4) ◽  
pp. 1317-1329 ◽  
Author(s):  
D. R. Rounce ◽  
D. C. McKinney
Keyword(s):  
Thermal Conductivity ◽  
Energy Balance ◽  
Temperature Gradient ◽  
Satellite Imagery ◽  
Energy Balance Model ◽  
Shortwave Radiation ◽  
Balance Model ◽  
Thermal Conductivity Model ◽  
Nonlinear Temperature ◽  
Elevation Model

Abstract. Debris thickness is an important characteristic of 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 Enhanced Thematic Mapper Plus (ETM+) satellite imagery to derive thermal resistances, which are the debris thickness divided by the thermal conductivity. Model results are reported in terms of debris thickness using an effective thermal conductivity derived from field data. The developed model accounts for the nonlinear temperature gradient in the debris cover to derive reasonable debris thicknesses. Fieldwork performed on Imja–Lhotse Shar Glacier in September 2013 was used to compare to the modeled debris thicknesses. Results indicate that accounting for the nonlinear temperature gradient is crucial. Furthermore, correcting the incoming shortwave radiation term for the effects of topography and resampling to the resolution of the thermal band's pixel is imperative to deriving reasonable debris thicknesses. Since the topographic correction is important, the model will improve with the quality of the digital elevation model (DEM). The main limitation of this work is the poor resolution (60 m) of the satellite's thermal band. The derived debris thicknesses are reasonable at this resolution, but trends related to slope and aspect are unable to be modeled on a finer scale. Nonetheless, the study finds this model derives reasonable debris thicknesses on this scale and was applied to other debris-covered glaciers in the Everest region.

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.

An Energy Balance Model for a Direct Methanol Fuel Cell

2011 ◽  
Author(s):  
Yu-Jen Chiu ◽  
Yen-Ling Lin
Keyword(s):  
Fuel Cell ◽  
Energy Balance ◽  
Temperature Gradient ◽  
Direct Methanol Fuel Cell ◽  
Management Strategies ◽  
Energy Balance Model ◽  
Utilization Efficiency ◽  
Balance Model ◽  
Direct Methanol ◽  
Methanol Fuel Cell

Fuel cell is a kind of devices that generates electricity and heat via electrochemical reactions. Accompanying the development of relevant applications, the efficiency issue has received more and more interest. In the duration of electricity generation, a variety of polarization losses will disperse in the form of heat. Higher electricity efficiency leads to lower heat generation, and vice versa. The amount of the generated heat correlates with the temperature gradient of the fuel flow along the stack channel. For a direct methanol fuel cell (DMFC), both the fuel utilization efficiency and fuel concentration are essential indices for the system. However, it is much complicated to acquire them. As a result, it will be a feasible and valuable approach to correlate these indices with the temperature gradient. In this work, an energy balance model of a DMFC is established to investigate factors that contribute thermal influences on the system. Based on the model, the relationship between efficiency and temperature gradient is derived. The proposed model may serve as the basis of water and thermal management strategies, which are beneficial for enhancing the performance and reliability of such a power generation system.

scholarly journals Debris-covered energy balance model for Imja-Lhotse Shar Glacier in the Everest region of Nepal

2015 ◽  
Vol 9 (3) ◽  
pp. 3503-3540 ◽  
Author(s):  
D. R. Rounce ◽  
D. J. Quincey ◽  
D. C. McKinney
Keyword(s):  
Thermal Conductivity ◽  
Heat Flux ◽  
Surface Roughness ◽  
Energy Balance ◽  
Latent Heat ◽  
Latent Heat Flux ◽  
Energy Balance Model ◽  
Balance Model ◽  
Glacier Surface ◽  
Supraglacial Lakes

Abstract. Debris thickness plays an important role in regulating ablation rates on debris-covered glaciers as well as controlling the likely size and location of supraglacial lakes. Despite its importance, lack of knowledge about debris properties and associated energy fluxes prevents the robust inclusion of the effects of a debris layer into most glacier surface energy balance models. This study combines fieldwork with a debris-covered energy balance model to estimate debris temperatures and ablation rates on Imja-Lhotse Shar glacier located in the Everest region of Nepal. The debris properties that significantly influence the energy balance model are thermal conductivity, albedo, and surface roughness. Fieldwork was conducted to measure thermal conductivity and a method was developed using Structure from Motion to estimate surface roughness. Debris temperatures measured during the 2014 melt season were used to calibrate and validate a debris-covered energy balance model by optimizing the albedo, thermal conductivity, and surface roughness at 10 debris-covered sites. Furthermore, three methods for estimating the latent heat flux were investigated. Model calibration and validation found the three methods had similar performance; however, comparison of modeled and measured ablation rates revealed that assuming a zero latent heat flux may overestimate ablation. Results also suggest that where debris moisture is unknown, measurements of the relative humidity or precipitation may be used to estimate wet debris periods, i.e., the latent heat flux is non-zero. The effect of temporal resolution on the model was also assessed and results showed that both 6 h data and daily average data slightly underestimate debris temperatures and ablation rates, thus these should only be used to estimate rough ablation rates when no other data are available.

scholarly journals Distributed Melt on a Debris-Covered Glacier: Field Observations and Melt Modeling on the Lirung Glacier in the Himalaya

2021 ◽  
Vol 9 ◽  
Author(s):  
Jakob F. Steiner ◽  
Phillip D. A. Kraaijenbrink ◽  
Walter W. Immerzeel
Keyword(s):  
Thermal Conductivity ◽  
Energy Balance ◽  
Mass Loss ◽  
Promising Result ◽  
Monsoon Season ◽  
Energy Balance Model ◽  
Balance Model ◽  
High Temporal Resolution ◽  
High Mountain ◽  
The Himalaya

Debris-covered glaciers, especially in high-mountain Asia, have received increased attention in recent years. So far, few field-based observations of distributed mass loss exist and both the properties of the debris layer as well as the atmospheric drivers of melt below debris remain poorly understood. Using multi-year observations of on-glacier atmospheric data, debris properties and spatial surface elevation changes from repeat flights with an unmanned aerial vehicle (UAV), we quantify the necessary variables to compute melt for the Lirung Glacier in the Himalaya. By applying an energy balance model we reproduce observed mass loss during one monsoon season in 2013. We show that melt is especially sensitive to thermal conductivity and thickness of debris. Our observations show that previously used values in literature for the thermal conductivity through debris are valid but variability in space on a single glacier remains high. We also present a simple melt model, which is calibrated based on the results of energy balance model, that is only dependent on air temperature and debris thickness and is therefore applicable for larger scale studies. This simple melt model reproduces melt under thin debris (<0.5 m) well at an hourly resolution, but fails to represent melt under thicker debris accurately at this high temporal resolution. On the glacier scale and using only off-glacier forcing data we however are able to reproduce the total melt volume of a debris-covered tongue. This is a promising result for catchment scale studies, where quantifying melt from debris covered glaciers remains a challenge.

scholarly journals Modelling ice-cliff backwasting on a debris-covered glacier in the Nepalese Himalaya

2015 ◽  
Vol 61 (229) ◽  
pp. 889-907 ◽  
Author(s):  
Jakob F. Steiner ◽  
Francesca Pellicciotti ◽  
Pascal Buri ◽  
Evan S. Miles ◽  
Walter W. Immerzeel ◽  
...  
Keyword(s):  
Energy Balance ◽  
High Resolution ◽  
Shortwave Radiation ◽  
Balance Model ◽  
Point Scale ◽  
Radiative Fluxes ◽  
Digital Elevation ◽  
Local Topography ◽  
Elevation Model

AbstractIce cliffs have been identified as a reason for higher ablation rates on debris-covered glaciers than are implied by the insulation effects of the debris. This study aims to improve our understanding of cliff backwasting, and the role of radiative fluxes in particular. An energy-balance model is forced with new data gathered in May and October 2013 on Lirung Glacier, Nepalese Himalaya. Observations show substantial variability in melt between cliffs, between locations on any cliff and between seasons. Using a high-resolution digital elevation model we calculate longwave fluxes incident to the cliff from surrounding terrain and include the effect of local shading on shortwave radiation. This is an advance over previous studies, that made simplified assumptions on cliff geometry and radiative fluxes. Measured melt rates varied between 3.25 and 8.6 cm d−1 in May and 0.18 and 1.34 cm d−1 in October. Model results reproduce the strong variability in space and time, suggesting considerable differences in radiative fluxes over one cliff. In October the model fails to reproduce stake readings, probably due to the lack of a refreezing component. Disregarding local topography can lead to overestimation of melt at the point scale by up to ∼9%.

scholarly journals Distributed Energy Balance Flux Modelling of Mass Balances in the Artesonraju Glacier and Discharge in the Basin of Artesoncocha, Cordillera Blanca, Peru

Climate ◽  
2021 ◽  
Vol 9 (9) ◽  
pp. 143
Author(s):  
María Fernanda Lozano Gacha ◽  
Manfred Koch
Keyword(s):  
Energy Balance ◽  
Mass Balance ◽  
Energy Balance Model ◽  
Shortwave Radiation ◽  
Radiative Energy ◽  
Balance Model ◽  
Threshold Temperature ◽  
Mass Balances ◽  
Distributed Energy ◽  
Cordillera Blanca

A distributed energy balance model (DEBAM) is applied to estimate the mass balance of the Artesonraju glacier in the Cordillera Blanca (CB), Peru, and to simulate the ensuing discharge into its respective basin, Artesoncocha. The energy balance model calibrations show that, by using seasonal albedos, reasonable results for mass balances and discharge can be obtained, as witnessed by annually aggregated Nash Sutcliffe coefficients (E) of 0.60–0.87 for discharge and of 0.58–0.71 for mass measurements carried out in the period 2004–2007. Mass losses between −1.42 and −0.45 m.w.e. are calculated for that period. The elevation line altitudes (ELAs), which lie between 5009 and 5050 m.a.s.l., are also well simulated, compared to those measured by the Unidad Glaciologica de Recursos Hídricos del Perú (UGRH). It is demonstrated that the net radiation which drives the energy balance and melting processes is mainly affected by the amount of reflected shortwave radiation from the different surfaces. Moreover, the longwave radiation sinks between 63 and 73% of solar radiative energy in the dry season. Further sensitivity studies indicate that the assumed threshold temperature T0 is crucial in mass balance simulations, as it determines the extension of areas with different albedos. An optimal T0 between 2.6 and 3.8 °C is deduced from these simulations.

scholarly journals Satellite-Based Water and Energy Balance Model for the Arid Region to Determine Evapotranspiration: Development and Application

2021 ◽  
Vol 13 (23) ◽  
pp. 13111
Author(s):  
Ahsan Ali ◽  
Yaseen A. Al-Mulla ◽  
Yassine Charabi ◽  
Ghazi Al-Rawas ◽  
Malik Al-Wardy
Keyword(s):  
Energy Balance ◽  
Satellite Imagery ◽  
Sap Flow ◽  
Arid Region ◽  
Large Scale ◽  
Management Practices ◽  
Sensible Heat Flux ◽  
Energy Balance Model ◽  
Balance Model

Actual evapotranspiration (ETa) plays an important role in irrigation planning and supervision. Traditionally, the estimation of ETa was approximated using different in situ techniques, having high initial and maintenance costs with low spatial resolution. In this context, satellite imagery models play an effective role in water management practices by estimating ETa in small and large-scale areas. All existing models have been widely used for the estimation of ETa around the globe, but there is no definite conclusion on which approach is best for the hot and hyper-arid region of Oman. Our study introduces an innovative approach that uses in situ, meteorological, and satellite imagery (Landsat-OLI/TIRS) datasets to estimate ETa. The satellite-based water and energy balance model for the arid region to determine evapotranspiration (SMARET) was developed under the hot and hyper-arid region conditions of Oman by incorporating soil temperature in the sensible heat flux. The performance of SMARET ran through accuracy assessment against in situ measurements via sap flow sensors and lysimeters. The SMARET was also evaluated against three existing models, including the surface energy balance algorithm for land (SEBAL), mapping evapotranspiration at high-resolution with internalized calibration (METRIC), and the Penman–Monteith (PM) model. The study resulted in a significant correlation between SMARET (R2 = 0.73), as well as the PM model (R2 = 0.72), and the ETa values calculated from Lysimeter. The SMARET model also showed a significant correlation (R2 = 0.66) with the ETa values recorded using the sap flow meter. The strong relationship between SMARET, sap flow measurement, and lysimeter observation suggests that SMARET has application capability in hot and hyper-arid regions.

scholarly journals Debris-covered glacier energy balance model for Imja–Lhotse Shar Glacier in the Everest region of Nepal

2015 ◽  
Vol 9 (6) ◽  
pp. 2295-2310 ◽  
Author(s):  
D. R. Rounce ◽  
D. J. Quincey ◽  
D. C. McKinney
Keyword(s):  
Thermal Conductivity ◽  
Heat Flux ◽  
Surface Roughness ◽  
Energy Balance ◽  
Latent Heat ◽  
Latent Heat Flux ◽  
Energy Balance Model ◽  
Balance Model ◽  
Glacier Surface ◽  
Supraglacial Lakes

Abstract. Debris thickness plays an important role in regulating ablation rates on debris-covered glaciers as well as controlling the likely size and location of supraglacial lakes. Despite its importance, lack of knowledge about debris properties and associated energy fluxes prevents the robust inclusion of the effects of a debris layer into most glacier surface energy balance models. This study combines fieldwork with a debris-covered glacier energy balance model to estimate debris temperatures and ablation rates on Imja–Lhotse Shar Glacier located in the Everest region of Nepal. The debris properties that significantly influence the energy balance model are the thermal conductivity, albedo, and surface roughness. Fieldwork was conducted to measure thermal conductivity and a method was developed using Structure from Motion to estimate surface roughness. Debris temperatures measured during the 2014 melt season were used to calibrate and validate a debris-covered glacier energy balance model by optimizing the albedo, thermal conductivity, and surface roughness at 10 debris-covered sites. Furthermore, three methods for estimating the latent heat flux were investigated. Model calibration and validation found the three methods had similar performance; however, comparison of modeled and measured ablation rates revealed that assuming the latent heat flux is zero may overestimate ablation. Results also suggest that where debris moisture is unknown, measurements of the relative humidity or precipitation may be used to estimate wet debris periods, i.e., when the latent heat flux is non-zero. The effect of temporal resolution on the model was also assessed and results showed that both 6 h data and daily average data slightly underestimate debris temperatures and ablation rates; thus these should only be used to estimate rough ablation rates when no other data are available.

Sign in / Sign up

Export Citation Format

Share Document