scholarly journals Inferring snowpack ripening and melt-out from distributed measurements of near-surface ground temperatures

2012 ◽  
Vol 6 (5) ◽  
pp. 1127-1139 ◽  
Author(s):  
M.-O. Schmid ◽  
S. Gubler ◽  
J. Fiddes ◽  
S. Gruber
Keyword(s):  
Ground Surface ◽  
Spatial Clusters ◽  
Near Surface ◽  
Ground Temperatures ◽  
M 10 ◽  
Surface Temperatures ◽  
Ground Freezing ◽  
Melting Characteristics ◽  
Seasonal Snow Cover ◽  
Ground Material

Abstract. Seasonal snow cover and its melt regime are heterogeneous both in time and space. Describing and modelling this variability is important because it affects diverse phenomena such as runoff, ground temperatures or slope movements. This study presents the derivation of melting characteristics based on spatial clusters of ground surface temperature (GST) measurements. Results are based on data from Switzerland where ground surface temperatures were measured with miniature loggers (iButtons) at 40 locations referred to as footprints. At each footprint, up to ten iButtons have been distributed randomly over an area of 10 m × 10 m, placed a few cm below the ground surface. Footprints span elevations of 2100–3300 m a.s.l. and slope angles of 0–55°, as well as diverse slope expositions and types of surface cover and ground material. Based on two years of temperature data, the basal ripening date and the melt-out date are determined for each iButton, aggregated to the footprint level and further analysed. The melt-out date could be derived for nearly all iButtons; the ripening date could be extracted for only approximately half of them because its detection based on GST requires ground freezing below the snowpack. The variability within a footprint is often considerable and one to three weeks difference between melting or ripening of the points in one footprint is not uncommon. The correlation of mean annual ground surface temperatures, ripening date and melt-out date is moderate, suggesting that these metrics are useful for model evaluation.

scholarly journals Inferring snow pack ripening and melt out from distributed ground surface temperature measurements

2012 ◽  
Vol 6 (1) ◽  
pp. 563-591
Author(s):  
M.-O. Schmid ◽  
S. Gubler ◽  
J. Fiddes ◽  
S. Gruber
Keyword(s):  
Ground Surface ◽  
Temperature Measurements ◽  
Snow Pack ◽  
Spatial Clusters ◽  
Ground Temperatures ◽  
Surface Temperatures ◽  
Ground Freezing ◽  
Melting Characteristics ◽  
Seasonal Snow Cover ◽  
Ground Material

Abstract. The seasonal snow cover and its melting are heterogeneous both in space and time. Describing and modelling this variability are important because it affects divers phenomena such as runoff, ground temperatures or slope movements. This study investigates the derivation of melting characteristics based on spatial clusters of temperature measurements. Results are based on data from Switzerland where ground surface temperatures were measured with miniature loggers (iButtons) at 40 locations, referred to as footprints. At each footprint, ten iButtons have been distributed randomly few cm below the ground surface over an area of 10 m × 10 m. Footprints span elevations of 2100–3300 m a.s.l. and slope angles of 0–55°, as well as diverse slope expositions and types of surface cover and ground material. Based on two years of temperature data, the basal ripening date and the melt-out date are determined for each iButton, aggregated to the footprint level and further analysed. The date of melt out could be derived for nearly all iButtons, the ripening date could be extracted for only approximately half of them because it requires ground freezing below the snow pack. The variability within a footprint is often considerable and one to three weeks difference between melting or ripening of the points in one footprint is not uncommon. The correlation of mean annual ground surface temperatures, ripening date and melt-out date is moderate, making them useful intuitive complementary measured for model evaluation.

Relations between air and surface temperature in discontinuous permafrost terrain near Mayo, Yukon Territory

2004 ◽  
Vol 41 (12) ◽  
pp. 1437-1451 ◽  
Author(s):  
K C Karunaratne ◽  
C R Burn
Keyword(s):  
Surface Temperature ◽  
Ground Surface ◽  
Absolute Temperature ◽  
Yukon Territory ◽  
Near Surface ◽  
Ground Temperatures ◽  
Surface Temperatures ◽  
Air Temperatures ◽  
Discontinuous Permafrost ◽  
Data Loggers

The association of site characteristics with the n-factor, a ratio of air to ground surface temperature, was investigated at five sites in the boreal forest near Mayo, Yukon Territory. Permafrost was in equilibrium with surface conditions at three sites, was degrading at another, and was absent from the fifth. Air and near-surface ground temperatures were recorded by data loggers between September 2000 and April 2002, and mean daily temperatures were accumulated to calculate n-factors for the freezing (nf) and thawing (nt) seasons. Air temperature did not vary between the sites, so inter-site differences in nf and nt were because of variations in surface temperature. Variations in nf between the sites over the two winters were primarily because of differences in snow depth, but at sites with similar snow cover, the surface temperatures were relatively high when the site was underlain by unfrozen ground. During summer, daily mean surface temperatures were initially less than air temperatures. However, once the thawing front had penetrated below the depth of diurnal temperature fluctuation, the air and ground surface temperatures converged. Since the rate of thaw penetration is governed by soil thermal diffusivity, nt varies directly with this property. These results indicate that subsurface conditions, particularly absolute temperature and ground thermal properties, exert considerable influence on n-factors, and, at the Mayo sites, the influence is greater than that of the vegetation.

scholarly journals Small-scale variation of snow in a regional permafrost model

2016 ◽  
Vol 10 (3) ◽  
pp. 1201-1215 ◽  
Author(s):  
Kjersti Gisnås ◽  
Sebastian Westermann ◽  
Thomas Vikhamar Schuler ◽  
Kjetil Melvold ◽  
Bernd Etzelmüller
Keyword(s):  
Snow Cover ◽  
Ground Surface ◽  
Grid Cell ◽  
Ground Temperature ◽  
Fine Tuning ◽  
Small Scale ◽  
Near Surface ◽  
Ground Temperatures ◽  
Surface Temperatures ◽  
Scale Variation

Abstract. The strong winds prevalent in high altitude and arctic environments heavily redistribute the snow cover, causing a small-scale pattern of highly variable snow depths. This has profound implications for the ground thermal regime, resulting in highly variable near-surface ground temperatures on the metre scale. Due to asymmetric snow distributions combined with the nonlinear insulating effect of snow, the spatial average ground temperature in a 1 km2 area cannot be determined based on the average snow cover for that area. Land surface or permafrost models employing a coarsely classified average snow depth will therefore not yield a realistic representation of ground temperatures. In this study we employ statistically derived snow distributions within 1 km2 grid cells as input to a regional permafrost model in order to represent sub-grid variability of ground temperatures. This improves the representation of both the average and the total range of ground temperatures. The model reproduces observed sub-grid ground temperature variations of up to 6 °C, and 98 % of borehole observations match the modelled temperature range. The mean modelled temperature of the grid cell reproduces the observations with an accuracy of 1.5 °C or better. The observed sub-grid variations in ground surface temperatures from two field sites are very well reproduced, with estimated fractions of sub-zero mean annual ground surface temperatures within ±10 %. We also find that snow distributions within areas of 1 km2 in Norwegian mountain environments are closer to a gamma than to a lognormal theoretical distribution. The modelled permafrost distribution seems to be more sensitive to the choice of distribution function than to the fine-tuning of the coefficient of variation. When incorporating the small-scale variation of snow, the modelled total permafrost area of mainland Norway is nearly twice as large compared to the area obtained with grid-cell average snow depths without a sub-grid approach.

scholarly journals Ground thermal and geomechanical conditions in a permafrost-affected high-latitude rockslide site (Polvartinden, Northern Norway)

2016 ◽  
Author(s):  
Regula Frauenfelder ◽  
Ketil Isaksen ◽  
Jeannette Nötzli ◽  
Matthew J. Lato
Keyword(s):  
Temperature Regime ◽  
Laser Scanning ◽  
Ground Surface ◽  
Failure Zone ◽  
Climate Data ◽  
Conduction Model ◽  
Near Surface ◽  
Northern Norway ◽  
Surface Temperatures

Abstract. In June 2008, a rockslide detached in the northeast facing slope of Polvartinden, a high-alpine mountain in Signaldalen, Northern Norway. Here, we report on the observed and modelled past and present near-surface temperature regime close to the failure zone, as well as on a subsequent simulation of the subsurface temperature regime, and on initial geomechanical mapping based on laser scanning. The volume of the rockslide was estimated to be approximately 500 000 m3. The depth to the actual failure surface was found to range from 40 m at the back of the failure zone to 0 m at its toe. Visible in-situ ice was observed in the failure zone just after the rockslide. Between September 2009 and August 2013 ground surface temperatures were measured with miniature temperature data loggers at fourteen different localities close to the original failure zone along the northern ridge of Polvartinden, and in the valley floor. The results from these measurements and from a basic three-dimensional heat conduction model suggest that the lower altitudinal limit of permafrost at present is at 600–650 m a.s.l., which corresponds to the upper limit of the failure zone. A coupling of our in-situ data with regional climate data since 1958 suggests a general gradual warming and that a period with highest mean near surface temperatures on record ended four months before the Signaldalen rockslide detached. A comparison with a transient permafrost model run at 10 m depth, representative for areas where snow accumulates, strengthen this findings, which are also in congruence with measurements in nearby permafrost boreholes. It is likely that permafrost in and near the failure zone is presently subject to degradation. This degradation, in combination with the extreme warm year antecedent to the rock failure, is seen to have played an important role in the detaching of the Signaldalen rockslide.

Assessing Arctic Ground Surface Temperatures from Borehole Temperatures and Paleoclimatic Model Simulations

2021 ◽  
Author(s):  
Hugo Beltrami ◽  
Fracisco José Cuesta-Valero ◽  
Almudena García-García ◽  
Stephan Gruber ◽  
Fernando Jaume-Santero
Keyword(s):  
Surface Temperature ◽  
Ground Surface ◽  
Phase Iii ◽  
The Arctic ◽  
Depth Range ◽  
Model Simulations ◽  
Ground Temperatures ◽  
Surface Temperatures ◽  
Intercomparison Project ◽  
Borehole Temperature

<p>The surface temperature response to changes in our planet’s external forcing is larger at higher latitudes, a phenomenon known as polar amplification. The Arctic amplification has been particularly intense during the last century, with arctic-wide paleoclimatic reconstructions and state-of-the-art model simulations revealing a twofold arctic warming in comparison with the average global temperature increase. As a consequence, Arctic ground temperatures respond with rapid warming, but this response varies with snow cover and permafrost processes. Thus, changes in arctic ground temperatures are difficult to reconstruct from data, and to simulate in climate models.</p><p>Here, we reconstruct the ground surface temperature histories of 120 borehole temperature profiles above 60ºN for the last 400 years. Past surface temperature evolution from each profile was estimated using a Perturbed Parameter Inversion approach based on a singular value decomposition method. Long-term surface temperature climatologies (circa 1300 and 1700 CE) and quasi-steady state heat flow are also estimated from linear regression through the depth range 200 to 300 m of each borehole temperature profile. The retrieved temperatures are assessed against simulated ground surface temperatures from five Past Millennium and five Historical experiments from the Paleoclimate Modelling Intercomparison Project Phase III (PMIP3), and the fifth phase of the Coupled Model Intercomparison Project (CMIP5) archives, respectively.</p><p>Preliminary results from borehole estimates and PMIP3/CMIP5 simulations reveal that changes in recent Arctic ground temperatures vary spatially and are related to each site’s earlier thermal state of the surface. The magnitudes of ground warming from data and simulations differ with large discrepancies among models. As a consequence, a better understanding of freezing processes at and below the air-ground interface is necessary to interpret subsurface temperature records and global climate model simulations in the Arctic.</p>

scholarly journals Thermal Submeso Motions in the Nocturnal Stable Boundary Layer. Part 2: Generating Mechanisms and Implications

2021 ◽  
Author(s):  
Lena Pfister ◽  
Karl Lapo ◽  
Larry Mahrt ◽  
Christoph K. Thomas
Keyword(s):  
Boundary Layer ◽  
Stable Boundary Layer ◽  
Side Wall ◽  
Cold Pool ◽  
Continuous Data ◽  
Valley Bottom ◽  
Near Surface ◽  
Cold Air ◽  
Stable Boundary ◽  
Surface Temperatures

AbstractIn the stable boundary layer, thermal submesofronts (TSFs) are detected during the Shallow Cold Pool experiment in the Colorado plains, Colorado, USA in 2012. The topography induces TSFs by forming two different air layers converging on the valley-side wall while being stacked vertically above the valley bottom. The warm-air layer is mechanically generated by lee turbulence that consistently elevates near-surface temperatures, while the cold-air layer is thermodynamically driven by radiative cooling and the corresponding cold-air drainage decreases near-surface temperatures. The semi-stationary TSFs can only be detected, tracked, and investigated in detail when using fibre-optic distributed sensing (FODS), as point observations miss TSFs most of the time. Neither the occurrence of TSFs nor the characteristics of each air layer are connected to a specific wind or thermal regime. However, each air layer is characterized by a specific relationship between the wind speed and the friction velocity. Accordingly, a single threshold separating different flow regimes within the boundary layer is an oversimplification, especially during the occurrence of TSFs. No local forcings or their combination could predict the occurrence of TSFs except that they are less likely to occur during stronger near-surface or synoptic-scale flow. While classical conceptualizations and techniques of the boundary layer fail in describing the formation of TSFs, the use of spatially continuous data obtained from FODS provide new insights. Future studies need to incorporate spatially continuous data in the horizontal and vertical planes, in addition to classic sensor networks of sonic anemometry and thermohygrometers to fully characterize and describe boundary-layer phenomena.

scholarly journals Summer temperature response to extreme soil water conditions in the Mediterranean transitional climate regime

2021 ◽  
Author(s):  
Stefano Materia ◽  
Constantin Ardilouze ◽  
Chloé Prodhomme ◽  
Markus G. Donat ◽  
Marianna Benassi ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Soil Moisture ◽  
Soil Water ◽  
Land Surface ◽  
Heat Waves ◽  
Climate Regime ◽  
Seasonal Forecasts ◽  
Near Surface ◽  
Surface Temperatures ◽  
The Mediterranean

AbstractLand surface and atmosphere are interlocked by the hydrological and energy cycles and the effects of soil water-air coupling can modulate near-surface temperatures. In this work, three paired experiments were designed to evaluate impacts of different soil moisture initial and boundary conditions on summer temperatures in the Mediterranean transitional climate regime region. In this area, evapotranspiration is not limited by solar radiation, rather by soil moisture, which therefore controls the boundary layer variability. Extremely dry, extremely wet and averagely humid ground conditions are imposed to two global climate models at the beginning of the warm and dry season. Then, sensitivity experiments, where atmosphere is alternatively interactive with and forced by land surface, are launched. The initial soil state largely affects summer near-surface temperatures: dry soils contribute to warm the lower atmosphere and exacerbate heat extremes, while wet terrains suppress thermal peaks, and both effects last for several months. Land-atmosphere coupling proves to be a fundamental ingredient to modulate the boundary layer state, through the partition between latent and sensible heat fluxes. In the coupled runs, early season heat waves are sustained by interactive dry soils, which respond to hot weather conditions with increased evaporative demand, resulting in longer-lasting extreme temperatures. On the other hand, when wet conditions are prescribed across the season, the occurrence of hot days is suppressed. The land surface prescribed by climatological precipitation forcing causes a temperature drop throughout the months, due to sustained evaporation of surface soil water. Results have implications for seasonal forecasts on both rain-fed and irrigated continental regions in transitional climate zones.

scholarly journals Late Weichselian thermal state at the base of the Scandinavian Ice Sheet

2019 ◽  
Author(s):  
Dmitry Y. Demezhko ◽  
Anastasia A. Gornostaeva ◽  
Alexander N. Antipin
Keyword(s):  
Thermal State ◽  
Ice Sheet ◽  
Ground Surface ◽  
Substantial Part ◽  
Temperature Pattern ◽  
Glacial Cycle ◽  
Surface Temperatures ◽  
Scandinavian Ice Sheet ◽  
Late Weichselian ◽  
The Last Glacial

Abstract. Geothermal estimates of the ground surface temperatures for the last glacial cycle in Northern Europe has been analyzed. During the Middle and Late Weichselian (55–12 kyr BP) a substantial part of this area was covered by the Scandinavian Ice Sheet. The analysis of geothermal data has allowed reconstructing limits of the ice sheet extension and its basal thermal state in the Late Weichselian. Ground surface temperatures outside the ice sheet were extremely low (from −8 to −18 °C). Within the ice sheet, there were both thawed and frozen zones. The revealed temperature pattern is generally consistent with the modern one for the ground surface temperatures in Greenland that makes it possible to consider these ice sheets as analogues. The anomalous climatically induced surface heat flux and orbital insolation of the Earth varied consistently outside the glaciation and independently within the limits of the ice sheet.

scholarly journals Simultaneous lithospheric-atmospheric signals of acoustic emission at “Karymshina” site in Kamchatka

2021 ◽  
Vol 254 ◽  
pp. 02013
Author(s):  
Igor Larionov ◽  
Yuriy Marapulets ◽  
Mikhail Mishchenko
Keyword(s):  
Acoustic Emission ◽  
Active Region ◽  
Ground Surface ◽  
Wide Band ◽  
Kamchatka Peninsula ◽  
Acoustic Signals ◽  
Rock Deformation ◽  
Acoustic System ◽  
Near Surface ◽  
Atmosphere Interaction

We present the results of complex lithospheric-atmospheric investigations of acoustic emission in a seismically active region (Kamchatka peninsula). A laser strainmeter-interferometer, a geophone, a wide-band acoustic system and a microbarometer, installed at Karymshina site (IKIR FEB RAS), are used in the monitoring. Rock deformation, acoustic emission in the near-surface rocks and in the atmosphere by the ground surface are under the consideration. Moreover, we suggest a method to detect acoustic signals recorded simultaneously in the near-surface rocks and in the atmosphere by the ground surface. The method consists in filtration of acoustic signals from the sensors at different frequency sub-ranges from fractions to the first hundreds of hertz followed by detection and accumulation of on 1-second interval. We analyze the data from September 2016 to December 2020. Examples of records of simultaneous acoustic signals in rocks and in the atmosphere are illustrated. The investigation is topical for the construction of a model of lithosphere-atmosphere interaction in a seismically active region.

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