scholarly journals Spatio-temporal flow variations driving heat exchange processes at a mountain glacier

2020 ◽  
Vol 14 (12) ◽  
pp. 4699-4718
Author(s):  
Rebecca Mott ◽  
Ivana Stiperski ◽  
Lindsey Nicholson
Keyword(s):  
Heat Exchange ◽  
Wind System ◽  
Local Wind ◽  
Glacier Surface ◽  
Near Surface ◽  
Heat Advection ◽  
Centre Line ◽  
Air Temperatures ◽  
Exchange Processes ◽  
Glacier Flow

Abstract. Multi-scale interactions between the glacier surface, the overlying atmosphere, and the surrounding alpine terrain are highly complex and force temporally and spatially variable local glacier energy fluxes and melt rates. A comprehensive measurement campaign (Hintereisferner Experiment, HEFEX) was conducted during August 2018 with the aim to investigate spatial and temporal dynamics of the near-surface boundary layer and associated heat exchange processes close to the glacier surface during the melting season. The experimental set-up of five meteorological stations was designed to capture the spatial and temporal characteristics of the local wind system on the glacier and to quantify the contribution of horizontal heat advection from surrounding ice-free areas to the local energy flux variability at the glacier. Turbulence data suggest that temporal changes in the local wind system strongly affect the micrometeorology at the glacier surface. Persistent low-level katabatic flows during both night and daytime cause consistently low near-surface air temperatures with only small spatial variability. However, strong changes in the local thermodynamic characteristics occur when westerly flows disturbed this prevailing katabatic flow, forming across-glacier flows and facilitating warm-air advection from the surrounding ice-free areas. Such heat advection significantly increased near-surface air temperatures at the glacier, resulting in strong horizontal temperature gradients from the peripheral zones towards the centre line of the glacier. Despite generally lower near-surface wind speeds during across-glacier flow, peak horizontal heat advection from the peripheral zones towards the centre line and strong transport of turbulence from higher atmospheric layers downward resulted in enhanced turbulent heat exchange towards the glacier surface at the glacier centre line. Thus, at the centre line of the glacier, exposure to strong larger-scale westerly winds promoted heat exchange processes, potentially contributing to ice melt, while at the peripheral zones of the glacier, stronger sheltering from larger-scale flows allowed the preservation of a katabatic jet, which suppressed the efficiency of the across-glacier flow to drive heat exchange towards the glacier surface by decoupling low-level atmospheric layers from the flow aloft. A fuller explanation of the origin and structure of the across-glacier flow would require large-eddy simulations.

scholarly journals Insights into the effect of spatial and temporal flow variations on turbulent heat exchange at a mountain glacier

2020 ◽  
Author(s):  
Rebecca Mott ◽  
Ivana Stipserki ◽  
Lindsey Nicholson ◽  
Jordan Mertes
Keyword(s):  
Heat Exchange ◽  
Turbulent Heat ◽  
Glacier Surface ◽  
Near Surface ◽  
Low Level ◽  
Air Temperatures ◽  
Exchange Processes ◽  
Turbulent Heat Exchange ◽  
Turbulence Data ◽  
Glacier Flow

Abstract. Multi-scale interactions between the glacier surface, the overlying atmosphere and the surrounding alpine terrain are highly complex. The high heterogeneity of boundary layer processes that couple these systems drives temporally and spatially variable energy fluxes and melt rates. A comprehensive measurement campaign, the HEFEX (Hintereisferner Experiment), was conducted during the summer of 2018. The aim of this experiment was to investigate spatial and temporal dynamics of the near-surface boundary layer and associated heat exchange processes close to the glacier surface during the melting season. The experimental setup of five meteorological stations was designed to capture the spatial and temporal characteristics of the local wind system on the glacier and to quantify the contribution of horizontal heat advection from surrounding ice-free areas to the local energy flux variability at the glacier. Turbulence data suggest that the temporal change in the local wind system strongly affect the micrometeorology at the glacier. Low-level katabatic flows were persistently measured during both night time and daytime and were responsible for consistently low near-surface air temperatures with small spatial variations at the glacier. On the contrary, local turbulence profiles of momentum and heat revealed strong changes of the local thermodynamic characteristics at the glacier when larger-scale westerly flows disturbed the prevailing katabatic flow forming low-level across-glacier flows. Warm air advection from the surrounding ice-free areas significantly increased near-surface air-temperatures at the glacier, with strong horizontal temperature gradients from the peripheral zones towards the centerline of the glacier. Despite generally lower near-surface wind speeds during the across-glacier flow, peak horizontal heat advection from the peripheral zones towards the centerline and strong transport of turbulence from higher atmospheric layers downward resulted in enhanced turbulent heat exchange towards the glacier surface at the glacier centerline. Thus, at the centerline of the glacier the exposure to strong larger-scale westerly winds promoted heat exchange processes at the glacier surface potentially contributing to ice melt. On the contrary, at the peripheral zones of the glacier turbulence data indicate that stronger sheltering from the larger-scale flows allowed the preservation of a katabatic jet, which suppressed the efficiency of the across-glacier flow to drive heat exchange towards the glacier surface by decoupling low-level atmospheric layers from the flow aloft. To explain the origin of the across-glacier flow would however require large eddy simulations.

Analyzing Near Surface Temperature Inversions Across the Greenland Ice Sheet Using In-situ, Remote Sensing, and Reanalysis Data

2020 ◽  
Author(s):  
Alden Adolph ◽  
Wesley Brown ◽  
Karina Zikan ◽  
Robert Fausto
Keyword(s):  
Surface Temperature ◽  
Energy Exchange ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Near Surface ◽  
Surface Temperatures ◽  
Air Temperatures ◽  
Exchange Processes ◽  
Temperature Inversions

<p>As Arctic temperatures have increased, the Greenland Ice Sheet has exhibited a negative mass balance, with a substantial and increasing fraction of mass loss due to surface melt. Understanding surface energy exchange processes in Greenland is critical for our ability to predict changes in mass balance. In-situ and remotely sensed surface temperatures are useful for monitoring trends, melt events, and surface energy balance processes, but these observations are complicated by the fact that surface temperatures and near surface air temperatures can significantly differ due to the presence of inversions that exist across the Arctic. Our previous work shows that even in the summer, very near surface inversions are present between the 2m air and surface temperatures a majority of the time at Summit, Greenland. In this study, we expand upon these results and combine a variety of data sources to quantify differences between surface snow/ice temperatures and 2m air temperatures across the Greenland Ice Sheet and investigate controls on the magnitude of these near surface temperature inversions. In-situ temperatures, wind speed, specific humidity, and albedo data are provided from automatic weather stations operated by the Programme for Monitoring of the Greenland Ice Sheet (PROMICE). We use the Clouds and the Earth's Radiant Energy System (CERES) cloud area fraction data to analyze effects of cloud presence on near surface temperature gradients. The in-situ temperatures are compared to Modern-Era Retrospective analysis for Research and Applications Version 2 (MERRA-2) and Moderate Resolution Imaging Spectrometer (MODIS) ice surface temperature data to extend findings across the ice sheet. Using PROMICE in-situ data from 2015, we find that these 2m temperature inversions are present 77% of the time, with a median strength of 1.7°C. The data confirm that the presence of clouds weakens inversions. Initial results indicate a RMSE of 3.9°C between MERRA-2 and PROMICE 2m air temperature, and a RMSE of 5.6°C between the two datasets for surface temperature. Improved understanding of controls on near surface inversions is important for use of remotely sensed snow surface temperatures and for modeling of surface mass and energy exchange processes.</p>

Increase of Heat Exchange Processes Efficiency at Production Site

2017 ◽  
pp. 18-21
Author(s):  
A.F. Khasanova ◽  
◽  
M.A. Gallyamov ◽  
Z.A. Zakirova ◽  
◽  
...  
Keyword(s):  
Heat Exchange ◽  
Production Site ◽  
Exchange Processes

scholarly journals Seasonal Influence of Insolation on Fine-Resolved Air Temperature Variation and Snowmelt

2014 ◽  
Vol 53 (2) ◽  
pp. 323-332 ◽  
Author(s):  
Nikki Vercauteren ◽  
Steve W. Lyon ◽  
Georgia Destouni
Keyword(s):  
Solar Radiation ◽  
Snow Cover ◽  
Eastern Coast ◽  
Seasonal Influence ◽  
Near Surface ◽  
Average Temperature ◽  
Monthly Average ◽  
Air Temperatures ◽  
Low Performance ◽  
Snow Cover Duration

AbstractThis study uses GIS-based modeling of incoming solar radiation to quantify fine-resolved spatiotemporal responses of year-round monthly average temperature within a field study area located on the eastern coast of Sweden. A network of temperature sensors measures surface and near-surface air temperatures during a year from June 2011 to June 2012. Strong relationships between solar radiation and temperature exhibited during the growing season (supporting previous work) break down in snow cover and snowmelt periods. Surface temperature measurements are here used to estimate snow cover duration, relating the timing of snowmelt to low performance of an existing linear model developed for the investigated site. This study demonstrates that linearity between insolation and temperature 1) may only be valid for solar radiation levels above a certain threshold and 2) is affected by the consumption of incoming radiation during snowmelt.

scholarly journals ON THE SOLUTION OF ENERGY BALANCE EQUATION SYSTEM TO PREDICT TEMPERATURE DISTRIBUTION IN THE BUILDING ELEMENTS WITH VENTILATED AIR GAP

2014 ◽  
Vol 21 (1) ◽  
pp. 21-30 ◽  
Author(s):  
Edmundas Monstvilas ◽  
Karolis Banionis ◽  
Jurga Poderytė ◽  
Raimondas Bliūdžius ◽  
Arūnas Burlingis
Keyword(s):  
Heat Exchange ◽  
Balance Equation ◽  
Heat Balance ◽  
Internal Surface ◽  
Equation System ◽  
Energy Balance Equation ◽  
Air Gap ◽  
Exchange Processes ◽  
Calculation Results ◽  
Thermal Indicators

The article presents the solution of heat balance equation system, describing heat exchange processes in ventilated envelopes, which was applied to derive formulas for the calculation of temperatures in the ventilated layers of the envelopes. The accurateness of the formulas was assessed by experimental research and analysis of the calculation results. During the process of heat exchange balance equation solution, the equations were simplified by introducing the following restriction into the derived formulas: they may only be applied for the ventilated envelopes with steel or similar coatings as their external layers, i.e. coatings having small heat capacity and minor difference between the external and internal surface temperatures. The derived formulas enable the calculation of the temperatures of the ventilated envelopes in the distance which does not exceed a half of the ventilated air gap length measuring from the air entrance into the gap. However, this restriction does not impede the estimation of the average thermal indicators of the ventilated envelopes.

scholarly journals Seasonal dynamics of methane emissions from a subarctic fen in the Hudson Bay Lowlands

2013 ◽  
Vol 10 (7) ◽  
pp. 4465-4479 ◽  
Author(s):  
K. L. Hanis ◽  
M. Tenuta ◽  
B. D. Amiro ◽  
T. N. Papakyriakou
Keyword(s):  
Soil Temperature ◽  
Air Temperature ◽  
Growing Season ◽  
Near Surface ◽  
Growing Seasons ◽  
Air Temperatures ◽  
Soil Temperatures ◽  
Surface Soil Temperature ◽  
Filling Method ◽  
Highly Correlated

Abstract. Ecosystem-scale methane (CH4) flux (FCH4) over a subarctic fen at Churchill, Manitoba, Canada was measured to understand the magnitude of emissions during spring and fall shoulder seasons, and the growing season in relation to physical and biological conditions. FCH4 was measured using eddy covariance with a closed-path analyser in four years (2008–2011). Cumulative measured annual FCH4 (shoulder plus growing seasons) ranged from 3.0 to 9.6 g CH4 m−2 yr−1 among the four study years, with a mean of 6.5 to 7.1 g CH4 m−2 yr−1 depending upon gap-filling method. Soil temperatures to depths of 50 cm and air temperature were highly correlated with FCH4, with near-surface soil temperature at 5 cm most correlated across spring, fall, and the shoulder and growing seasons. The response of FCH4 to soil temperature at the 5 cm depth and air temperature was more than double in spring to that of fall. Emission episodes were generally not observed during spring thaw. Growing season emissions also depended upon soil and air temperatures but the water table also exerted influence, with FCH4 highest when water was 2–13 cm below and lowest when it was at or above the mean peat surface.

scholarly journals Characterizing near-surface firn using the scattered signal component of the glacier surface return from airborne radio-echo sounding

2016 ◽  
Vol 43 (24) ◽  
pp. 12,502-12,510 ◽  
Author(s):  
Anja Rutishauser ◽  
Cyril Grima ◽  
Martin Sharp ◽  
Donald D. Blankenship ◽  
Duncan A. Young ◽  
...  
Keyword(s):  
Scattered Signal ◽  
Glacier Surface ◽  
Near Surface ◽  
Signal Component ◽  
Radio Echo Sounding ◽  
Echo Sounding

scholarly journals Solar Dryer with Integrated Energy Unit

2021 ◽  
Vol 2(50) ◽  
Author(s):  
Sergey Korobka ◽  
◽  
Sergey Syrotyuk ◽  
Dmitry Zhuravel ◽  
Boris Boltianskyi ◽  
...  
Keyword(s):  
Heat Exchange ◽  
Solar Energy ◽  
Moisture Transfer ◽  
Diagnostic Techniques ◽  
Material Surface ◽  
Drying Process ◽  
Energy Unit ◽  
Solar Dryer ◽  
Exchange Processes ◽  
Deformed State

The work is devoted to the issue of the rational use of the solar energy in the technological process of fruit drying based on the use of solar drying devices, which are applied in various sections of the agro-industrial centers of Ukraine. The aim of this research was intensification of the fruits drying process using the solar energy by combining an air collector and drying chamber into a single power unit. To achieve the aim the heat exchange diagnostic techniques with alternative potentials of diffusion and moisture transfer was developed. This technique differs from those existing for the heat exchange research in that it allows the intensity of the moisture evaporation from a unit of the material surface to be calculated, based on the synthesis of the moisture content and the irreversible major laws of processes of the heat exchange characteristics of the fruits drying using the solar dryer. The above model makes it possible to diagnose the heat exchange processes and analyze the mathematical model of the heat exchange processes. It also allows modeling the changeable diffusion and moisture transfer potentials based on the dependences obtained and for the purpose of a further application in the methods and devices development to control the strain-deformed state of the fruits during the drying process. The method is offered for the calculation of diffusion and moisture transfer during drying fruits in the solar dryer.

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