scholarly journals Resolving Small‐Scale Forest Snow Patterns Using an Energy Balance Snow Model With a One‐Layer Canopy

2020 ◽  
Vol 56 (1) ◽  
Author(s):  
Giulia Mazzotti ◽  
Richard Essery ◽  
C. David Moeser ◽  
Tobias Jonas
Keyword(s):  
Energy Balance ◽  
Small Scale ◽  
Snow Model

scholarly journals Snow specific surface area simulation using the one-layer snow model in the Canadian LAnd Surface Scheme (CLASS)

2013 ◽  
Vol 7 (3) ◽  
pp. 961-975 ◽  
Author(s):  
A. Roy ◽  
A. Royer ◽  
B. Montpetit ◽  
P. A. Bartlett ◽  
A. Langlois
Keyword(s):  
Energy Balance ◽  
Surface Energy ◽  
Liquid Water ◽  
Land Surface ◽  
Surface Energy Balance ◽  
Liquid Water Content ◽  
Canadian Land Surface Scheme ◽  
Snow Model ◽  
Surface Scheme ◽  
The One

Abstract. Snow grain size is a key parameter for modeling microwave snow emission properties and the surface energy balance because of its influence on the snow albedo, thermal conductivity and diffusivity. A model of the specific surface area (SSA) of snow was implemented in the one-layer snow model in the Canadian LAnd Surface Scheme (CLASS) version 3.4. This offline multilayer model (CLASS-SSA) simulates the decrease of SSA based on snow age, snow temperature and the temperature gradient under dry snow conditions, while it considers the liquid water content of the snowpack for wet snow metamorphism. We compare the model with ground-based measurements from several sites (alpine, arctic and subarctic) with different types of snow. The model provides simulated SSA in good agreement with measurements with an overall point-to-point comparison RMSE of 8.0 m2 kg–1, and a root mean square error (RMSE) of 5.1 m2 kg–1 for the snowpack average SSA. The model, however, is limited under wet conditions due to the single-layer nature of the CLASS model, leading to a single liquid water content value for the whole snowpack. The SSA simulations are of great interest for satellite passive microwave brightness temperature assimilations, snow mass balance retrievals and surface energy balance calculations with associated climate feedbacks.

scholarly journals HERschel Observations of Edge-on Spirals (HEROES)

2018 ◽  
Vol 616 ◽  
pp. A120 ◽  
Author(s):  
Aleksandr V. Mosenkov ◽  
Flor Allaert ◽  
Maarten Baes ◽  
Simone Bianchi ◽  
Peter Camps ◽  
...  
Keyword(s):  
Energy Balance ◽  
Near Infrared ◽  
Complex Geometry ◽  
Dust Emission ◽  
Three Dimensional ◽  
Stellar Model ◽  
Small Scale ◽  
Balance Study ◽  
Balance Problem ◽  
Double Exponential

We present results of the detailed dust energy balance study for the seven large edge-on galaxies in the HEROES sample using three-dimensional (3D) radiative transfer (RT) modelling. Based on available optical and near-infrared (NIR) observations of the HEROES galaxies, we derive the 3D distribution of stars and dust in these galaxies. For the sake of uniformity, we apply the same technique to retrieve galaxy properties for the entire sample: we use a stellar model consisting of a Sérsic bulge and three double-exponential discs (a superthin disc for a young stellar population and thin and thick discs for old populations). For the dust component, we adopt a double-exponential disc with the new THEMIS dust-grain model. We fit oligochromatic RT models to the optical and NIR images with the fitting algorithm FITSKIRT and run panchromatic simulations with the SKIRT code at wavelengths ranging from ultraviolet to submillimeter. We confirm the previously stated dust energy balance problem in galaxies: for the HEROES galaxies, the dust emission derived from our RT calculations underestimates the real observations by a factor 1.5–4 for all galaxies except NGC 973 and NGC 5907 (apparently, the latter galaxy has a more complex geometry than we used). The comparison between our RT simulations and the observations at mid-infrared–submillimetre wavelengths shows that most of our galaxies exhibit complex dust morphologies (possible spiral arms, star-forming regions, more extended dust structure in the radial and vertical directions). We suggest that, in agreement with results from the literature, the large- and small-scale structure is the most probable explanation for the dust energy balance problem.

scholarly journals Hα Emission from the Magellanic Bridge

2007 ◽  
Vol 24 (2) ◽  
pp. 69-76 ◽  
Author(s):  
E. Muller ◽  
Q. A. Parker
Keyword(s):  
Energy Balance ◽  
Molecular Hydrogen ◽  
Preliminary Report ◽  
Stellar Population ◽  
Line Emission ◽  
Turbulent Structure ◽  
Small Scale ◽  
Hα Emission

AbstractWe present here a preliminary report and commentary of recently processed observations of Hα emission towards the Magellanic Bridge. These data have been analysed in an attempt to quantify the extent to which the stellar population is capable of reshaping the local ISM. We find that the Hα emission regions are small, weak and sparsely distributed, consistent with a relatively quiescent and inactive ISM where radiative and collisional ionisation is inefficient and sporadic. This suggests that energetic processes at the small scale (i.e. ∼tens of pc) do not dominate the energy balance within the ISM of the Bridge, which therefore hosts a pristine turbulent structure, otherwise inaccessible within our own Galaxy. We find Hα emission that is well correlated with detected 12CO(1–0) line emission (a proxy for molecular hydrogen), as well as other easily identified ring-like Hı features.

scholarly journals Self-similarity in glacier surface characteristics

2003 ◽  
Vol 49 (167) ◽  
pp. 547-554 ◽  
Author(s):  
Neil S. Arnold ◽  
W. Gareth Rees
Keyword(s):  
Surface Roughness ◽  
Energy Balance ◽  
Spatial Variability ◽  
Snow Depth ◽  
Surface Albedo ◽  
Small Scale ◽  
Late Winter ◽  
Glacier Surface ◽  
Correlation Lengths ◽  
Aerodynamic Roughness

AbstractCatchment-wide information on glacier snow-cover depth, surface albedo and surface roughness is important input data for distributed models of glacier energy balance. In this study, we investigate the small-scale (mm to 100 m) spatial variability in these properties, with a view to better simulating this variability in such models. Data were collected on midre Lovénbreen, a 6 km2 valley glacier in northwest Svalbard. The spatial variability of all three properties was found to be self-similar over the range of scales under investigation. Snow depth and albedo exhibit a correlation length within which measurements were spatially autocorrelated. Late-winter and summer properties of snow depth differed, with smaller depths in summer due to melt, and shorter correlation lengths. Similar correlation lengths for snow depth and surface albedo may suggest that snow-depth variation is an important control on the small-scale spatial variability of glacier surface albedo. For surface roughness, the data highlight a possible problem in energy-balance studies which use microtopographic surveys to calculate aerodynamic roughness, in that the scale of the measurements made affects the calculated roughness value. This suggests that further investigations of the relationships between surface form and aerodynamic roughness of glacier surfaces are needed.

scholarly journals A two-layer canopy with thermal inertia for an improved modelling of the sub-canopy snowpack energy-balance

2015 ◽  
Vol 8 (1) ◽  
pp. 209-262 ◽  
Author(s):  
I. Gouttevin ◽  
M. Lehning ◽  
T. Jonas ◽  
D. Gustafsson ◽  
M. Mölder
Keyword(s):  
Energy Balance ◽  
Temperature Drop ◽  
Model Performance ◽  
Thermal Inertia ◽  
Thermal Response ◽  
Canopy Temperature ◽  
Night Time ◽  
The Difference ◽  
Snow Model ◽  
The Impact

Abstract. A new, two-layer canopy module with thermal inertia as part of the detailed snow model SNOWPACK (version 3.2.1) is presented and evaluated. This module is designed to reproduce the difference in thermal response between leafy and woody canopy elements, and their impact on the underlying snowpack energy balance. Given the number of processes resolved, the SNOWPACK model with its enhanced canopy module constitutes a very advanced, physics-based atmosphere-to-soil-through-canopy-and-snow modelling chain. Comparisons of modelled sub-canopy thermal radiation to stand-scale observations at an Alpine site (Alptal, Switzerland) demonstrate the improvements of the new canopy module. Both thermal heat mass and the two-layer canopy formulation contribute to reduce the daily amplitude of the modelled canopy temperature signal, in agreement with observations. Particularly striking is the attenuation of the night-time drop in canopy temperature, which was a key model bias. We specifically show that a single-layered canopy model is unable to produce this limited temperature drop correctly. The impact of the new parameterizations on the modelled dynamics of the sub-canopy snowpack is analysed and yields consistent results but the frequent occurrence of mixed-precipitation events at Alptal prevents a conclusive assessment of model performance against snow data. The new model is also successfully tested without specific tuning against measured tree temperatures and biomass heat storage fluxes at the boreal site of Norunda (Sweden). This provides an independent assessment of its physical consistency and stresses the robustness and transferability of the parameterizations used.

scholarly journals Variations of ablation, albedo and energy balance at the margin of the Greenland ice sheet, Kronprins Christian Land, eastern north Greenland

1995 ◽  
Vol 41 (137) ◽  
pp. 174-182 ◽  
Author(s):  
Thomas Konzelmann ◽  
Roger J. Braithwaite
Keyword(s):  
Heat Flux ◽  
Energy Balance ◽  
Latent Heat ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Small Scale ◽  
Conductive Heat ◽  
Net Radiation ◽  
Conductive Heat Flux ◽  
North Greenland

AbstractA meteorological and glaciological experiment was carried out in July 1993 at the margin of the Greenland ice sheet in Kronprins Christian Land, eastern north Greenland. Within a small area (about 100 m2) daily measurements were made on ten ablation stakes fixed in “light” and “dark” ice and were compared to each other. Simultaneously, the components of the energy balance, including net radiation, sensible-heat flux, latent-heat flux and conductive-heat flux in the ice were determined. Global radiation, longwave incoming radiation and albedo were measured, and longwave outgoing radiation was calculated by assuming that the glacier surface was melting. Sensible-and latent-heat fluxes were calculated from air temperature, humidity and wind speed. Conductive-heat flux in the ice was estimated by temperature-profile measurements in the uppermost ice layer. Net radiation is the major source of ablation energy, and turbulent fluxes are smaller energy sources by about three times, while heat flux into the ice is a substantial heat sink, reducing energy available for ice melt. Albedo varies from 0.42 to 0.56 within the experimental site and causes relatively large differences in ablation at stakes close to each other. Small-scale albedo variations should therefore be carefully sampled for large-scale energy-balance calculations.

scholarly journals Using 3D turbulence-resolving simulations to understand the impact of surface properties on the energy balance of a debris-covered glacier

2019 ◽  
Author(s):  
Pleun N. J. Bonekamp ◽  
Chiel C. van Heerwaarden ◽  
Jakob F. Steiner ◽  
Walter W. Immerzeel
Keyword(s):  
Energy Balance ◽  
Surface Properties ◽  
Turbulent Fluxes ◽  
Specific Humidity ◽  
Meteorological Variables ◽  
Small Scale ◽  
High Mountain ◽  
Conductive Heat ◽  
Glacier Melt ◽  
The Impact

Abstract. Debris-covered glaciers account for 18 % of the total glacier ice volume in High Mountain Asia, however the drivers controlling the melt of these glaciers are still largely unknown and their total contribution to the total glacier melt remains uncertain. Debris influences the surface energy balance and therefore glacier melt by influencing the thermal properties (e.g. albedo, thermal conductivity, roughness) of the glacier surface. In this study, the impact of surface properties of debris on the spatial distribution of micro meteorological variables, such as the turbulent fluxes, wind fields, moisture and temperature and eventually the conductive heat flux for a debris-covered glacier is investigated. We simulated a debris-covered glacier (Lirung Glacier, Nepal) at a high-resolution of 1 m with the MicroHH model with boundary conditions retrieved from an automatic weather station (temperature, wind and specific humidity) and UAV flights (digital elevation map and surface temperature), and the model is validated with eddy covariance data. Subsequently, a sensitivity analysis was performed to ascertain how heterogeneous surface variables control the glacier micro-climate. Additionally, we show ice cliffs are local melt hot spots and that turbulent fluxes and local heat advection amplify spatial heterogeneity on the surface. The high spatial variability of small-scale meteorological variables suggests that point based station observations cannot be simply extrapolated to an entire glacier and should be considered in future studies for a better estimation of glacier melt in High Mountain Asia.

scholarly journals Direct Insertion of NASA Airborne Snow Observatory‐Derived Snow Depth Time Series Into the iSnobal Energy Balance Snow Model

2018 ◽  
Vol 54 (10) ◽  
pp. 8045-8063 ◽  
Author(s):  
Andrew R. Hedrick ◽  
Danny Marks ◽  
Scott Havens ◽  
Mark Robertson ◽  
Micah Johnson ◽  
...  
Keyword(s):  
Time Series ◽  
Energy Balance ◽  
Snow Depth ◽  
Snow Model

scholarly journals Using 3D turbulence-resolving simulations to understand the impact of surface properties on the energy balance of a debris-covered glacier

2020 ◽  
Vol 14 (5) ◽  
pp. 1611-1632
Author(s):  
Pleun N. J. Bonekamp ◽  
Chiel C. van Heerwaarden ◽  
Jakob F. Steiner ◽  
Walter W. Immerzeel
Keyword(s):  
Energy Balance ◽  
Surface Properties ◽  
Turbulent Fluxes ◽  
Specific Humidity ◽  
Small Scale ◽  
High Mountain ◽  
Conductive Heat ◽  
Glacier Surface ◽  
Glacier Melt ◽  
The Impact

Abstract. Debris-covered glaciers account for almost one-fifth of the total glacier ice volume in High Mountain Asia; however, their contribution to the total glacier melt remains uncertain, and the drivers controlling this melt are still largely unknown. Debris influences the properties (e.g. albedo, thermal conductivity, roughness) of the glacier surface and thus the surface energy balance and glacier melt. In this study we have used sensitivity tests to assess the effect of surface properties of debris on the spatial distribution of micrometeorological variables such as wind fields, moisture and temperature. Subsequently we investigated how those surface properties drive the turbulent fluxes and eventually the conductive heat flux of a debris-covered glacier. We simulated a debris-covered glacier (Lirung Glacier, Nepal) at a 1 m resolution with the MicroHH model, with boundary conditions retrieved from an automatic weather station (temperature, wind and specific humidity) and unmanned aerial vehicle flights (digital elevation map and surface temperature). The model was validated using eddy covariance data. A sensitivity analysis was then performed to provide insight into how heterogeneous surface variables control the glacier microclimate. Additionally, we show that ice cliffs are local melt hot spots and that turbulent fluxes and local heat advection amplify spatial heterogeneity on the surface. The high spatial variability of small-scale meteorological variables suggests that point-based station observations cannot be simply extrapolated to an entire glacier. These outcomes should be considered in future studies for a better estimation of glacier melt in High Mountain Asia.

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