scholarly journals Turbulent fluxes above the snow surface

1998 ◽  
Vol 26 ◽  
pp. 179-183 ◽  
Author(s):  
Eric Martin ◽  
Yves Lejeune
Keyword(s):  
Surface Energy Balance ◽  
Meteorological Data ◽  
Energy Balance Equation ◽  
Turbulent Fluxes ◽  
Heat Fluxes ◽  
Indirect Measurements ◽  
Radiative Fluxes ◽  
Stable Conditions ◽  
Sonic Anemometers ◽  
Snow Model

Measurements of sensible- and latent-heat fluxes under stable conditions are rare. In order to obtain indirect measurements of turbulent fluxes, meteorological data measured at the Col de Porte laboratory (1320 m a.s.l, France) under very stable conditions (cold, clear night with low wind) are used. The radiative fluxes are measured, the conduction within the snowpack is calculated using the snow model Crocus and the turbulent fluxes are determined as a residual term of the surface-energy balance equation. These data were used to fit a new parameterization of the turbulent fluxes for the snow model. The turbulent fluxes are increased as compared to the theory. Crocus was also applied to the data from the LEADEX92 experiment and the turbulent fluxes calculated by the model were compared to the fluxes measured using sonic anemometers/thermometers on the site.

scholarly journals Turbulent fluxes above the snow surface

1998 ◽  
Vol 26 ◽  
pp. 179-183 ◽  
Author(s):  
Eric Martin ◽  
Yves Lejeune
Keyword(s):  
Surface Energy Balance ◽  
Meteorological Data ◽  
Energy Balance Equation ◽  
Turbulent Fluxes ◽  
Heat Fluxes ◽  
Indirect Measurements ◽  
Radiative Fluxes ◽  
Stable Conditions ◽  
Sonic Anemometers ◽  
Snow Model

Measurements of sensible- and latent-heat fluxes under stable conditions are rare. In order to obtain indirect measurements of turbulent fluxes, meteorological data measured at the Col de Porte laboratory (1320 m a.s.l, France) under very stable conditions (cold, clear night with low wind) are used. The radiative fluxes are measured, the conduction within the snowpack is calculated using the snow modelCrocusand the turbulent fluxes are determined as a residual term of the surface-energy balance equation. These data were used to fit a new parameterization of the turbulent fluxes for the snow model. The turbulent fluxes are increased as compared to the theory.Crocuswas also applied to the data from the LEADEX92 experiment and the turbulent fluxes calculated by the model were compared to the fluxes measured using sonic anemometers/thermometers on the site.

scholarly journals Areal melt and discharge modelling of Storglaciären, Sweden

1997 ◽  
Vol 24 ◽  
pp. 211-216 ◽  
Author(s):  
Regine Hock ◽  
Christian Noetzli
Keyword(s):  
Meteorological Data ◽  
Grid Point ◽  
Digital Terrain Model ◽  
Turbulent Fluxes ◽  
Heat Fluxes ◽  
Balance Model ◽  
Turbulent Heat ◽  
Terrain Model ◽  
Digital Terrain ◽  
One Year

A grid-based glacier melt-and-discharge model was applied to Storglaciären, a small valley glacier (3 km2) in northern Sweden, for the melt seasons of 1993 and 1994. The energy available for melt was estimated from a surface energy-balance model using meteorological data collected by automatic weather stations on the glacier. Net radiation and the turbulent heat fluxes were calculated hourly for every grid point of a 30 m resolution digital terrain model, using the measurements of temperature, humidity, wind speed and radiative fluxes on the glacier. Two different bulk approaches were used to calculate the turbulent fluxes and compared with respect to their impact on discharge simulations. Discharge of Storglaciären was simulated from calculated meltwater production and precipitation by three parallel linear reservoirs corresponding to the different storage properties of firn, snow and ice. The performance of the model was validated by comparing simulated discharge to measured discharge at the glacier snout. Depending on which parameterization of the turbulent fluxes was used, the timing and magnitude of simulated discharge was in good agreement with observed discharge, or simulated discharge was considerably underestimated in one year.

scholarly journals Diurnal land surface energy balance partitioning estimated from the thermodynamic limit of a cold heat engine

2018 ◽  
Author(s):  
Axel Kleidon ◽  
Maik Renner
Keyword(s):  
Energy Balance ◽  
Surface Energy ◽  
Thermodynamic Limit ◽  
Land Surface ◽  
Radiative Forcing ◽  
Surface Energy Balance ◽  
Heat Engine ◽  
Turbulent Fluxes ◽  
Heat Fluxes ◽  
Turbulent Heat

Abstract. Turbulent fluxes strongly shape the conditions at the land surface, yet they are typically formulated in terms of semi-empirical parameterisations that make it difficult to derive theoretical estimates of how global change impacts land surface functioning. Here, we describe these turbulent fluxes as the result of a thermodynamic process that generates work to sustain convective motion and thus maintains the turbulent exchange between the land surface and the atmosphere. We first derive a limit from the second law of thermodynamics that is equivalent to the Carnot limit, but which explicitly accounts for diurnal heat storage changes in the lower atmosphere. We then use this limit of a cold heat engine together with the surface energy balance to infer the maximum power that can be derived from the turbulent fluxes for a given solar radiative forcing. The surface energy balance partitioning estimated from this thermodynamic limit requires no empirical parameters and compares very well with the observed partitioning of absorbed solar radiation into radiative and turbulent heat fluxes across a range of climates, with correlation coefficients r2 ≥ 95 % and slopes near one. These results suggest that turbulent heat fluxes on land operate near their thermodynamic limit on how much convection can be generated from the local radiative forcing. It implies that this type of approach can be used to derive first-order estimates of global change that are solely based on physical principles.

Combined Diagram: A Graphical Representation of Combination Evaporation Rates

2012 ◽  
Vol 13 (4) ◽  
pp. 1389-1395
Author(s):  
Ricardo C. Muñoz
Keyword(s):  
Surface Layer ◽  
Water Vapor ◽  
Atmospheric Surface Layer ◽  
Surface Energy Balance ◽  
Graphical Representation ◽  
Energy Balance Equation ◽  
Heat Fluxes ◽  
Geometrical Analysis ◽  
Combination Methods ◽  
Transfer Equations

Abstract Combination methods estimate the partition of sensible and latent heat fluxes at the surface by combining the surface energy balance equation with the transfer equations for temperature and water vapor in the atmospheric surface layer. This paper presents a diagram that graphically depicts the main assumptions and steps of the method. Potential, apparent potential, and actual evaporation rates are visually explained with the diagram. Using a linearized saturation water content relation, the diagram permits the derivation of many of the combination evaporation results by means of geometrical analysis. The diagram should be helpful in the teaching and understanding of the combination methodology.

scholarly journals Areal melt and discharge modelling of Storglaciären, Sweden

1997 ◽  
Vol 24 ◽  
pp. 211-216 ◽  
Author(s):  
Regine Hock ◽  
Christian Noetzli
Keyword(s):  
Meteorological Data ◽  
Grid Point ◽  
Digital Terrain Model ◽  
Turbulent Fluxes ◽  
Heat Fluxes ◽  
Balance Model ◽  
Turbulent Heat ◽  
Terrain Model ◽  
Digital Terrain ◽  
One Year

A grid-based glacier melt-and-discharge model was applied to Storglaciären, a small valley glacier (3 km2) in northern Sweden, for the melt seasons of 1993 and 1994. The energy available for melt was estimated from a surface energy-balance model using meteorological data collected by automatic weather stations on the glacier. Net radiation and the turbulent heat fluxes were calculated hourly for every grid point of a 30 m resolution digital terrain model, using the measurements of temperature, humidity, wind speed and radiative fluxes on the glacier. Two different bulk approaches were used to calculate the turbulent fluxes and compared with respect to their impact on discharge simulations. Discharge of Storglaciären was simulated from calculated meltwater production and precipitation by three parallel linear reservoirs corresponding to the different storage properties of firn, snow and ice. The performance of the model was validated by comparing simulated discharge to measured discharge at the glacier snout. Depending on which parameterization of the turbulent fluxes was used, the timing and magnitude of simulated discharge was in good agreement with observed discharge, or simulated discharge was considerably underestimated in one year.

scholarly journals Quality Control and Tilt Correction Effects on the Turbulent Fluxes Observed at an Ocean Platform

2011 ◽  
Vol 50 (3) ◽  
pp. 700-712 ◽  
Author(s):  
Hyun-Mi Oh ◽  
Kyung-Eak Kim ◽  
Kyung-Ja Ha ◽  
Larry Mahrt ◽  
Jae-Seol Shim
Keyword(s):  
Quality Control ◽  
Fast Response ◽  
Correction Method ◽  
Turbulent Fluxes ◽  
The Yellow Sea ◽  
Research Station ◽  
Tilt Correction ◽  
Stable Conditions ◽  
Sonic Anemometers ◽  
Atmospheric Factors

Abstract This study investigates atmospheric factors influencing the quality and the postprocessing (e.g., tilt correction) of fast-response measurements of turbulent fluxes for difficult open-sea measurements over an offshore platform. The data were collected at the Ieodo Ocean Research Station over the Yellow Sea during the period from 5 November 2007 to 19 February 2008. The quality control removal of the data generally depends on wind speed, relative humidity, significant wave height, visibility, and stability. The removal of substantial water vapor data with weak-wind stable conditions is investigated. Three different tilt correction algorithms (double rotation, triple rotation, and planar fit) are applied to correct the data because of inadvertent tilt of sonic anemometers. The choice of tilt correction method significantly influences the angle between the wind and stress direction.

scholarly journals Diurnal land surface energy balance partitioning estimated from the thermodynamic limit of a cold heat engine

2018 ◽  
Vol 9 (3) ◽  
pp. 1127-1140 ◽  
Author(s):  
Axel Kleidon ◽  
Maik Renner
Keyword(s):  
Energy Balance ◽  
Surface Energy ◽  
Thermodynamic Limit ◽  
Land Surface ◽  
Radiative Forcing ◽  
Surface Energy Balance ◽  
Heat Engine ◽  
Turbulent Fluxes ◽  
Heat Fluxes ◽  
Turbulent Heat

Abstract. Turbulent fluxes strongly shape the conditions at the land surface, yet they are typically formulated in terms of semiempirical parameterizations that make it difficult to derive theoretical estimates of how global change impacts land surface functioning. Here, we describe these turbulent fluxes as the result of a thermodynamic process that generates work to sustain convective motion and thus maintains the turbulent exchange between the land surface and the atmosphere. We first derive a limit from the second law of thermodynamics that is equivalent to the Carnot limit but which explicitly accounts for diurnal heat storage changes in the lower atmosphere. We call this the limit of a “cold” heat engine and use it together with the surface energy balance to infer the maximum power that can be derived from the turbulent fluxes for a given solar radiative forcing. The surface energy balance partitioning estimated from this thermodynamic limit requires no empirical parameters and compares very well with the observed partitioning of absorbed solar radiation into radiative and turbulent heat fluxes across a range of climates, with correlation coefficients r2≥95 % and slopes near 1. These results suggest that turbulent heat fluxes on land operate near their thermodynamic limit on how much convection can be generated from the local radiative forcing. It implies that this type of approach can be used to derive general estimates of global change that are solely based on physical principles.

scholarly journals Analysis of meteorological data and the surface energy balance of McCall Glacier, Alaska, USA

2005 ◽  
Vol 51 (174) ◽  
pp. 451-461 ◽  
Author(s):  
E.J. Klok ◽  
M. Nolan ◽  
M.R. Van Den Broeke
Keyword(s):  
Energy Balance ◽  
Surface Energy ◽  
Mass Balance ◽  
Forest Fires ◽  
Surface Energy Balance ◽  
Meteorological Data ◽  
Heat Fluxes ◽  
Turbulent Heat ◽  
Net Radiation ◽  
Specific Mass

AbstractWe report on analysis of meteorological data for the period 27 May–20 August 2004, from two automatic weather stations on McCall Glacier, Alaska, USA, aimed at studying the relationship between climate and ablation. One station is located on a mountain ridge and the other in the ablation area where we also analyzed the energy balance. The weather station on the glacier measured an average temperature of 5.3°C (at 2 m height above surface) and wind speed of 3.1 m s−1 (at 3 m height). A sonic height ranger and ablation stakes indicate a specific mass balance of –1.94 ± 0.09 m w.e between 15 June and 20 August. The specific mass balance calculated from the surface energy balance, –2.06 ± 0.18 m w.e., is in close correspondence to this. The latter is the sum of 0.12 m w.e. of snowfall, 0.003 m w.e. of deposition and –2.18 m w.e. of melt. Net radiation contributes 74% of the melt energy. Compared to ablation measurements in the early 1970s, summer ablation was large. This increase is explained by a combination of a relatively higher net radiation, a lower albedo and larger turbulent heat fluxes that led to more energy being available for melting. No single meteorological variable can be isolated as being the principal reason for the high ablation, however. The lower ice albedo (0.19) is possibly due to ash deposits from forest fires.

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 Challenges in Modeling Turbulent Heat Fluxes to Snowpacks in Forest Clearings

2018 ◽  
Vol 19 (10) ◽  
pp. 1599-1616 ◽  
Author(s):  
Jonathan P. Conway ◽  
John W. Pomeroy ◽  
Warren D. Helgason ◽  
Nicholas J. Kinar
Keyword(s):  
Heat Exchange ◽  
Surface Temperature ◽  
Latent Heat ◽  
Turbulent Fluxes ◽  
Heat Fluxes ◽  
Turbulent Heat ◽  
Snow Surface ◽  
Turbulent Heat Exchange ◽  
Uncertainty Estimates ◽  
Model Tuning

Abstract Forest clearings are common features of evergreen forests and produce snowpack accumulation and melt differing from that in adjacent forests and open terrain. This study has investigated the challenges in specifying the turbulent fluxes of sensible and latent heat to snowpacks in forest clearings. The snowpack in two forest clearings in the Canadian Rockies was simulated using a one-dimensional (1D) snowpack model. A trade-off was found between optimizing against measured snow surface temperature or snowmelt when choosing how to specify the turbulent fluxes. Schemes using the Monin–Obukhov similarity theory tended to produce negatively biased surface temperature, while schemes that enhanced turbulent fluxes, to reduce the surface temperature bias, resulted in too much melt. Uncertainty estimates from Monte Carlo experiments showed that no realistic parameter set could successfully remove biases in both surface temperature and melt. A simple scheme that excludes atmospheric stability correction was required to successfully simulate surface temperature under low wind speed conditions. Nonturbulent advective fluxes and/or nonlocal sources of turbulence are thought to account for the maintenance of heat exchange in low-wind conditions. The simulation of snowmelt was improved by allowing enhanced latent heat fluxes during low-wind conditions. Caution is warranted when snowpack models are optimized on surface temperature, as model tuning may compensate for deficiencies in conceptual and numerical models of radiative, conductive, and turbulent heat exchange at the snow surface and within the snowpack. Such model tuning could have large impacts on the melt rate and timing of the snow-free transition in simulations of forest clearings within hydrological and meteorological models.

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