scholarly journals The surface energy balance of an active ice-covered volcano: Villarrica Volcano, southern Chile

2007 ◽  
Vol 45 ◽  
pp. 104-114 ◽  
Author(s):  
Benjamin Brock ◽  
Andrés Rivera ◽  
Gino Casassa ◽  
Francisca Bown ◽  
César Acuña
Keyword(s):  
Thermal Conductivity ◽  
Energy Balance ◽  
Field Data ◽  
Surface Energy Balance ◽  
Surface Material ◽  
Southern Chile ◽  
Villarrica Volcano ◽  
Tephra Thickness ◽  
Glacier Ablation ◽  
Highly Porous

AbstractThe energy balance of bare snow and tephra-covered ice near the glacier equilibrium line elevation on Villarrica Volcano, southern Chile, was investigated during 2004 and 2005, combining meteorological, surface temperature and ablation measurements with energy balance modelling. A tephra thermal conductivity of 0.35 Wm–1 K–1, and a critical tephra thickness of <5mm at which ablation is reduced compared to bare snow, were obtained from field data. These low values are attributable to the highly porous lapilli particles which make up most of the surface material. Modelled melt totals in the January to March period were 4.95 m and 3.96 m water equivalent (w.e.) in 2004 and 2005, respectively, compared with ∽0.5mw.e. melt for ice buried by >0.1m tephra. Windblown tephra impurities lowered snow albedo, but increased snowmelt by only an estimated 0.28mw.e. over the same period. The net mass balance impact of supraglacial tephra at Villarrica Volcano is therefore positive, as thick ash and lapilli mantle most of the glacier ablation zones, probably reducing annual ablation by several metres w.e. In the accumulation seasons, frequent melting events were recorded with modelled daily snowmelt rates of up to 50 mmw.e.

scholarly journals An energy-balance model for debris-covered glaciers including heat conduction through the debris layer

2010 ◽  
Vol 56 (199) ◽  
pp. 903-916 ◽  
Author(s):  
Tim D. Reid ◽  
Ben W. Brock
Keyword(s):  
Heat Conduction ◽  
Energy Balance ◽  
Heat Fluxes ◽  
Energy Balance Model ◽  
Balance Model ◽  
Physically Based ◽  
Villarrica Volcano ◽  
Using Data ◽  
Glacier Ablation ◽  
Miage Glacier

AbstractExtensive covers of supraglacial debris are often present in glacier ablation areas, and it is essential to assess exactly how the debris affects glacier melt rates. This paper presents a physically based energy-balance model for the surface of a debris-covered glacier. The model is driven by meteorological variables, and was developed using data collected at Miage glacier, Italy, during the ablation seasons of 2005, 2006 and 2007. The debris surface temperature is numerically estimated by considering the balance of heat fluxes at the air/debris interface, and heat conduction through the debris is calculated in order to estimate melt rates at the debris/ice interface. The predicted hourly debris surface temperatures and debris internal temperatures provide a good fit to temperatures measured on rock-covered Miage glacier (r2 >0.94) and the tephra-covered glacier on Villarrica volcano, Chile (r2 >0.82). The model can also be used to reproduce observed changes in melt rates below debris layers of varying types and thicknesses, an important consideration for the overall mass balance of debris-covered glaciers.

scholarly journals Surface energy balance of the Sygyktinsky Glacier, south Eastern Siberia, during the ablation period and its sensitivity to meteorological fluctuations

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Eduard Y. Osipov ◽  
Olga P. Osipova
Keyword(s):  
Energy Balance ◽  
Wind Speed ◽  
Surface Energy ◽  
Surface Energy Balance ◽  
Heat Fluxes ◽  
Shortwave Radiation ◽  
Eastern Siberia ◽  
Atmospheric Conditions ◽  
South Eastern ◽  
Glacier Ablation

AbstractThe physically based melt of the low elevation Eastern Siberian glaciers is poorly understood due to the lack of direct micrometeorological studies. We used an automatic meteorological station to record the meteorological and energy characteristics of the Sygyktinsky Glacier, south Eastern Siberia (56.8° N, 117.4° E, 2,560 m a.s.l.), during two ablation seasons and computed the surface energy balance (SEB) for 30-min intervals. The glacier ablation was both modeled and measured by stakes and a thermistor cable. The net radiation (Rnet) was the main contributor (71–75 W m−2, 89–95%) to the SEB (79 W m−2, 100%), followed by sensible (2–4 W m−2, 3–5%) and latent (2–3 W m−2, 2–4%) heat fluxes. The net shortwave radiation was the main positive component of Rnet, while the net longwave radiation was weak and either negative (− 15 W m−2 in 2019) or positive (4 W m−2 in 2020). The small proportion of turbulent fluxes in the SEB is explained by the low wind speed (1.2 m s−1). The glacier ablation was found to be more sensitive to changes in shortwave radiation and wind speed, suggesting the need to consider the atmospheric conditions of the ablation period (summer snowfalls, cloudiness, wind speed) when analyzing long-term trends in glacial changes.

scholarly journals Estimativa de evapotranspiração real a partir de imagens do sensor MODIS/AQUA e do algoritmo SEBAL na bacia do Rio Paranaíba – Brasil / Real evapotranspiration estimate from images of MODIS/AQUA sensor and SEBAL algorithm in Paranaíba river basin – Brazil

2019 ◽  
Vol 29 (57) ◽  
pp. 351-367
Author(s):  
Alécio Perini Martins ◽  
Roberto Rosa
Keyword(s):  
Energy Balance ◽  
Surface Energy ◽  
River Basin ◽  
Urban Areas ◽  
Field Data ◽  
Surface Energy Balance ◽  
Vegetation Coverage ◽  
Woody Vegetation ◽  
Use Of Data ◽  
Transmission And Absorption

A pesquisa visou avaliar a utilização de dados do sensor MODIS/AQUA para estimar valores de evapotranspiração real em superfície na bacia do Rio Paranaíba - Brasil. Foi utilizado o algoritmo SEBAL (Surface Energy Balance Algorithms for Land), desenvolvido a partir de princípios físicos envolvidos na reflexão, transmissão e absorção de energia pela superfície, necessitando de poucos dados de campo e, portanto, permitindo o estudo de extensas áreas. Foram obtidos valores médios de 3,4 mm/dia para evapotranspiração real, sendo os maiores valores observados nos meses de novembro e dezembro e os menores no mês de outubro. Corpos d’água e áreas com vegetação arbórea densa (formações florestais e silvicultura) apresentaram valores médios de evapotranspiração acima de 5 mm/dia, enquanto que em áreas urbanas e com solo sem cobertura vegetal esses valores médios não ultrapassaram 2 mm/dia.Palavras–chave: Evapotranspiração Real; Sensoriamento Remoto; Modelagem Climatológica.Abstract The research aimed to evaluate the use of data in sensor MODIS/AQUA to estimate values of real evapotranspiration in the surface of the Rio Paranaíba river basin - Brazil. We used the SEBAL algorithm (Surface Energy Balance Algorithms for Land), developed from physical principals involved in the reflection, transmission and absorption of energy by the surface, requiring few field data and, therefore, allowing the study of large areas. We obtained average values of 3.4 mm/day to real evapotranspiration, where the higher values were observed in November and December and the lowest ones in October. Water bodies and areas with dense woody vegetation (forests and forestry formations) presented average values of evapotranspiration above 5 mm/day, while in urban areas and with soil without vegetation coverage these values did not exceed 2 mm/day.Keywords: Real Evapotranspiration; Remote Sensing; Climatological Modeling.

Parametric Study of Photovoltaic Thermal Solar Collector Using An Improved Parallel Flow

2020 ◽  
Vol 2 (1) ◽  
pp. 19-24
Author(s):  
Sakhr Mohammed Sultan ◽  
Chih Ping Tso ◽  
Ervina Efzan Mohd Noor ◽  
Fadhel Mustafa Ibrahim ◽  
Saqaff Ahmed Alkaff
Keyword(s):  
Thermal Conductivity ◽  
Energy Balance ◽  
Parametric Study ◽  
Solar Collector ◽  
Parallel Flow ◽  
Operating Conditions ◽  
Balance Equations ◽  
Conductivity Type ◽  
Pv Module ◽  
Sunny Weather

Photovoltaic Thermal Solar Collector (PVT) is a hybrid technology used to produce electricity and heat simultaneously. Current enhancements in PVT are to increase the electrical and thermal efficiencies. Many PVT factors such as type of absorber, thermal conductivity, type of PV module and operating conditions are important parameters that can control the PVT performance. In this paper, an analytical model, using energy balance equations, is studied for PVT with an improved parallel flow absorber. The performance is calculated for a typical sunny weather in Malaysia. It was found that the maximum electrical and thermal efficiencies are 12.9 % and 62.6 %, respectively. The maximum outlet water temperature is 59 oC.

scholarly journals Using climate reanalysis data in conjunction with multi-temporal satellite thermal imagery to derive supraglacial debris thickness changes from energy-balance modelling

2021 ◽  
pp. 1-19
Author(s):  
Rebecca L. Stewart ◽  
Matthew Westoby ◽  
Francesca Pellicciotti ◽  
Ann Rowan ◽  
Darrel Swift ◽  
...  
Keyword(s):  
Energy Balance ◽  
Surface Energy ◽  
Surface Energy Balance ◽  
Current Knowledge ◽  
Meteorological Data ◽  
Reanalysis Data ◽  
Balance Model ◽  
Thermal Imagery ◽  
Thickness Estimation ◽  
Miage Glacier

Abstract Surface energy-balance models are commonly used in conjunction with satellite thermal imagery to estimate supraglacial debris thickness. Removing the need for local meteorological data in the debris thickness estimation workflow could improve the versatility and spatiotemporal application of debris thickness estimation. We evaluate the use of regional reanalysis data to derive debris thickness for two mountain glaciers using a surface energy-balance model. Results forced using ERA-5 agree with AWS-derived estimates to within 0.01 ± 0.05 m for Miage Glacier, Italy, and 0.01 ± 0.02 m for Khumbu Glacier, Nepal. ERA-5 data were then used to estimate spatiotemporal changes in debris thickness over a ~20-year period for Miage Glacier, Khumbu Glacier and Haut Glacier d'Arolla, Switzerland. We observe significant increases in debris thickness at the terminus for Haut Glacier d'Arolla and at the margins of the expanding debris cover at all glaciers. While simulated debris thickness was underestimated compared to point measurements in areas of thick debris, our approach can reconstruct glacier-scale debris thickness distribution and its temporal evolution over multiple decades. We find significant changes in debris thickness over areas of thin debris, areas susceptible to high ablation rates, where current knowledge of debris evolution is limited.

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 A Semiempirical Microscale Model of the Surface Energy Balance and Its Application to Two Urban Rooftops

2008 ◽  
Vol 47 (3) ◽  
pp. 819-834 ◽  
Author(s):  
Timothy M. Barzyk ◽  
John E. Frederick
Keyword(s):  
Energy Balance ◽  
Surface Energy ◽  
Surface Energy Balance ◽  
Balance Model ◽  
Site Specific ◽  
City Hall ◽  
Microscale Model ◽  
Dry Conditions ◽  
Stone Concrete ◽  
The City

Abstract Individual structures within the same local-scale (102–104 m) environment may experience different microscale (&lt;103 m) climates. Urban microclimate variations are often a result of site-specific features, including spatial and material characteristics of surfaces and surrounding structures. A semiempirical surface energy balance model is presented that incorporates radiative and meteorological measurements to statistically parameterize energy fluxes that are not measured directly, including sensible heat transport, storage heat flux through conduction, and evaporation (assumed to be negligible under dry conditions). Two Chicago rooftops were chosen for detailed study. The City Hall site was located in an intensely developed urban area characterized by close-set high-rise buildings. The University rooftop was in a highly developed area characterized by three- to seven-story buildings of stone, concrete, and brick construction. Two identical sets of instruments recorded measurements contemporaneously from these rooftops during summer 2005, and results from the week of 29 July to 5 August are presented here. The model explains 83.7% and 96% of the variance for the City Hall and University sites, respectively. Results apply to a surface area of approximately 1260 m2, at length scales similar to the dimensions of built structures and other urban elements. A site intercomparison revealed variations in surface energy balance components caused by site-specific features and demonstrated the relevance of the model to urban applications.

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