scholarly journals Monitoring Wet Snow Over an Alpine Region Using Sentinel-1 Observations

2021 ◽  
Vol 13 (3) ◽  
pp. 381
Author(s):  
Fatima Karbou ◽  
Gaëlle Veyssière ◽  
Cécile Coleou ◽  
Anne Dufour ◽  
Isabelle Gouttevin ◽  
...  
Keyword(s):  
Alpine Region ◽  
Geometric Distortion ◽  
Seasonal Snow ◽  
Area Of Interest ◽  
Wet Snow ◽  
Snow Distribution ◽  
Snow Conditions ◽  
Over Time ◽  
Sentinel 2 ◽  
Terrain Characteristics

The main objective of this study was to monitor wet snow conditions from Sentinel-1 over a season, to examine its variation over time by cross-checking wet snow with independent snow and weather estimates, and to study its distribution taking into account terrain characteristics such as elevation, orientation, and slope. One of our motivations was to derive useful representations of daily or seasonal snow changes that would help to easily identify wet snow elevations and determine melt-out days in an area of interest. In this work, a well-known approach in the literature is used to estimate the extent of wet snow cover continuously over a season and an analysis of the influence of complex mountain topography on snow distribution is proposed taking into account altitude, slope, and aspect of the terrain. The Sentinel-1 wet snow extent product was compared with Sentinel-2 snow products for cloud free scenes. We show that while there are good agreements between the two satellite products, differences exist, especially in areas of forests and glaciers where snow is underestimated. This underestimation must be considered alongside the areas of geometric distortion that were excluded from our study. We analysed retrievals at the scale of our study area by examining wet snow Altitude–Orientation diagrams for different classes of slopes and also wet snow Altitude–Time diagrams for different classes of orientations. We have shown that this type of representation is very useful to get an overview of the snow distribution as it allows to identify very easily wet snow lines for different orientations. For an orientation of interest, the Altitude–Time diagrams can be used to track the evolution of snow to locate altitudes and dates of snow loss. We also show that ascending/descending Sentinel-1 image time series are complementary to monitor wet snow over the French alpine areas to highlight wet snow altitude ranges and identify melt-out days. Links have also been made between Sentinel-1 responses (wet snow) and snow/meteorological events carefully listed over the entire 2017–2018 season.

scholarly journals In Situ Determination of Dry and Wet Snow Permittivity: Improving Equations for Low Frequency Radar Applications

2021 ◽  
Vol 13 (22) ◽  
pp. 4617
Author(s):  
Ryan W. Webb ◽  
Adrian Marziliano ◽  
Daniel McGrath ◽  
Randall Bonnell ◽  
Tate G. Meehan ◽  
...  
Keyword(s):  
Snow Water Equivalent ◽  
Low Frequency ◽  
Liquid Water Content ◽  
Seasonal Snow ◽  
Wet Snow ◽  
Primary Driver ◽  
Snow Water ◽  
Snow Conditions ◽  
Ground Penetrating

Extensive efforts have been made to observe the accumulation and melting of seasonal snow. However, making accurate observations of snow water equivalent (SWE) at global scales is challenging. Active radar systems show promise, provided the dielectric properties of the snowpack are accurately constrained. The dielectric constant (k) determines the velocity of a radar wave through snow, which is a critical component of time-of-flight radar techniques such as ground penetrating radar and interferometric synthetic aperture radar (InSAR). However, equations used to estimate k have been validated only for specific conditions with limited in situ validation for seasonal snow applications. The goal of this work was to further understand the dielectric permittivity of seasonal snow under both dry and wet conditions. We utilized extensive direct field observations of k, along with corresponding snow density and liquid water content (LWC) measurements. Data were collected in the Jemez Mountains, NM; Sandia Mountains, NM; Grand Mesa, CO; and Cameron Pass, CO from February 2020 to May 2021. We present empirical relationships based on 146 snow pits for dry snow conditions and 92 independent LWC observations in naturally melting snowpacks. Regression results had r2 values of 0.57 and 0.37 for dry and wet snow conditions, respectively. Our results in dry snow showed large differences between our in situ observations and commonly applied equations. We attribute these differences to assumptions in the shape of the snow grains that may not hold true for seasonal snow applications. Different assumptions, and thus different equations, may be necessary for varying snowpack conditions in different climates, suggesting that further testing is necessary. When considering wet snow, large differences were found between commonly applied equations and our in situ measurements. Many previous equations assume a background (dry snow) k that we found to be inaccurate, as previously stated, and is the primary driver of resulting uncertainty. Our results suggest large errors in SWE (10–15%) or LWC (0.05–0.07 volumetric LWC) estimates based on current equations. The work presented here could prove useful for making accurate observations of changes in SWE using future InSAR opportunities such as NISAR and ROSE-L.

scholarly journals Modelling liquid water transport in snow under rain-on-snow conditions – considering preferential flow

2017 ◽  
Vol 21 (3) ◽  
pp. 1741-1756 ◽  
Author(s):  
Sebastian Würzer ◽  
Nander Wever ◽  
Roman Juras ◽  
Michael Lehning ◽  
Tobias Jonas
Keyword(s):  
Water Transport ◽  
Liquid Water ◽  
Field Experiments ◽  
Preferential Flow ◽  
Richards Equation ◽  
European Alps ◽  
Wet Snow ◽  
Snow Conditions ◽  
Dual Domain ◽  
Grain Properties

Abstract. Rain on snow (ROS) has the potential to generate severe floods. Thus, precisely predicting the effect of an approaching ROS event on runoff formation is very important. Data analyses from past ROS events have shown that a snowpack experiencing ROS can either release runoff immediately or delay it considerably. This delay is a result of refreeze of liquid water and water transport, which in turn is dependent on snow grain properties but also on the presence of structures such as ice layers or capillary barriers. During sprinkling experiments, preferential flow was found to be a process that critically impacted the timing of snowpack runoff. However, current one-dimensional operational snowpack models are not capable of addressing this phenomenon. For this study, the detailed physics-based snowpack model SNOWPACK is extended with a water transport scheme accounting for preferential flow. The implemented Richards equation solver is modified using a dual-domain approach to simulate water transport under preferential flow conditions. To validate the presented approach, we used an extensive dataset of over 100 ROS events from several locations in the European Alps, comprising meteorological and snowpack measurements as well as snow lysimeter runoff data. The model was tested under a variety of initial snowpack conditions, including cold, ripe, stratified and homogeneous snow. Results show that the model accounting for preferential flow demonstrated an improved overall performance, where in particular the onset of snowpack runoff was captured better. While the improvements were ambiguous for experiments on isothermal wet snow, they were pronounced for experiments on cold snowpacks, where field experiments found preferential flow to be especially prevalent.

scholarly journals 3203 Collaboration in Reappointment, Promotion, and Tenure Guidelines

2019 ◽  
Vol 3 (s1) ◽  
pp. 130-131
Author(s):  
Jacqueline Knapke ◽  
John R. Kues ◽  
Stephanie M. Schuckman ◽  
Rebecca C. Lee
Keyword(s):  
Collaborative Work ◽  
Service Research ◽  
Promotion And Tenure ◽  
Common Coding ◽  
Research And Teaching ◽  
Area Of Interest ◽  
Interdisciplinary Approaches ◽  
Urban Institution ◽  
The University ◽  
Over Time

OBJECTIVES/SPECIFIC AIMS: As the issues facing our global society become more complex, university faculty are called upon to address these contemporary problems using interdisciplinary approaches. But do reappointment, promotion, and tenure (RPT) guidelines reflect and reward this fundamental change in the nature of higher education and scholarly inquiry? After collecting all of the RPT guidelines across the university, our research team at the University of Cincinnati (UC) conducted a content analysis of these documents to determine how collaborative work is defined, interpreted, and supported. In addition, we also sought to identify differences in how collaborative work is valued across disciplines and how that value has changed over time. METHODS/STUDY POPULATION: An initial database was assembled that included two distinct data samples: historical and current. Both included RPT criteria for over 100 disciplinary units at the university. Working with the initial comprehensive database, the team narrowed content by selecting all language related to collaborative work using several relevant keywords or keyword fragments (team, collaborat[*], disciplin[*], and interprofessional). This process resulted in a subset of data reflecting the area of interest that could then be coded. Three investigators independently coded common portions of the data for categories. The investigators met regularly to compare the results of their coding, and discrepancies between the investigators’ coding schemes were resolved through discussion. The final, common coding scheme will used to code the remainder of the data by each independent investigator. The team meets weekly to discuss significant passages and assign codes, and then reach consensus related to important themes that are identified. Specifically, we will examine the frequency with which collaborative activities are included, the value and emphasis given to them, and the differences across units. Having a historical sample and a current sample also allows us to analyze trends over time and further compare disciplinary differences. RESULTS/ANTICIPATED RESULTS: UC is a diverse institution that includes world-renowned creative schools (the College Conservatory of Music and the College of Design, Architecture, Art, and Planning), as well as traditional colleges of medicine, nursing, pharmacy, allied health, engineering, business, arts and sciences, etc. UC also includes two branch campuses that specialize in associate’s degree level education. Given the diversity in educational and research missions across these areas, we anticipate discovering several themes within the RPT guidelines, primarily centered around the traditional foundations of faculty work such as service, research, and teaching. We anticipate strong differences by college and disciplinary focus, with emphasis on collaborative work and engagement increasing as RPT guidelines become more current. DISCUSSION/SIGNIFICANCE OF IMPACT: Our experience is that faculty members want to engage in collaborative work when possible and appropriate, but their perception is that independent contributions to their field are more highly valued than interdisciplinary work. As universities rush to endorse and promote interdisciplinary, team-oriented research and teaching, this study will afford a better understanding of the types of activities valued at one large and diverse urban institution, grounded in the actual language of RPT criteria.

scholarly journals Sub-surface melting in a seasonal snow cover

1995 ◽  
Vol 41 (139) ◽  
pp. 474-482 ◽  
Author(s):  
Gary Koh ◽  
Rachel Jordan
Keyword(s):  
Surface Temperature ◽  
Snow Cover ◽  
Continuous Wave ◽  
Surface Melting ◽  
Balance Model ◽  
Fmcw Radar ◽  
Seasonal Snow ◽  
Wet Snow ◽  
Seasonal Snow Cover ◽  
Good Agreement

AbstractThe ability of solar radiation to penetrate into a snow cover combined with the low thermal conductivity of snow can lead to a sub-surface temperature maximum. This elevated sub-surface temperature allows a layer of wet snow to form below the surface even on days when the air temperature remains sub-freezing. A high-resolution frequency-modulated continuous wave (FMCW) radar has been used to detect the onset of sub-surface melting in a seasonal snow cover. The experimental observation of sub-surface melting is shown to be in good agreement with the predictions of a one-dimensional mass- and energy-balance model. The effects of varying snow characteristics and solar extinction parameters on the sub-surface melt characteristics are investigated using model simulations.

Inferences on flow mechanisms from snow avalanche deposits

2008 ◽  
Vol 49 ◽  
pp. 187-192 ◽  
Author(s):  
Dieter Issler ◽  
Alessia Errera ◽  
Stefano Priano ◽  
Hansueli Gubler ◽  
Bernardo Teufen ◽  
...  
Keyword(s):  
Swiss Alps ◽  
Snow Avalanches ◽  
Abrupt Decrease ◽  
Density Flow ◽  
Wet Snow ◽  
Flow Mechanisms ◽  
Snow Conditions ◽  
Distal Direction ◽  
Deposit Structure ◽  
Path Properties

AbstractThe deposit structure of 20 very small to large avalanches that occurred in the Davos area, eastern Swiss Alps, during winters 2004/05 and 2005/06 was investigated. Snow-cover entrainment was significant in the majority of events and likely to have occurred in all cases. Evidence was found both for plough-like frontal entrainment (especially in wet-snow avalanches) and more gradual erosion along the base of dry-snow avalanches. Several of the dry-snow avalanches, both small and large, showed a fairly abrupt decrease in deposit thickness in the distal direction, often accompanied by changes in the granulometry and the deposit density. Combined with other observations (snow plastered onto tree trunks, deposit-less flow marks in bends, etc.) and measurements at instrumented test sites, this phenomenon is best explained as being due to a fluidized, low-density flow regime that formed mostly in the head of some dry-snow avalanches. The mass fraction of the fluidized deposits ranged from less than 1% to ∼25% of the total deposit mass. Fluidization appears to depend rather sensitively on snow conditions and path properties.

Coping with pain in intimate situations: Applying the avoidance-endurance model to women with vulvovaginal pain

2017 ◽  
Vol 17 (1) ◽  
pp. 302-308 ◽  
Author(s):  
Ida Katrina Flink ◽  
Linnéa Engmana ◽  
Moniek M. Ter Kuile ◽  
Johanna Thomtén ◽  
Steven J. Linton
Keyword(s):  
Pain Catastrophizing ◽  
Coping Behaviors ◽  
Multiple Mediation ◽  
Sexual Activities ◽  
Area Of Interest ◽  
Women's Lives ◽  
And Coping ◽  
Significant Mediator ◽  
Mediation Models ◽  
Over Time

AbstractBackground and aimsChronic vulvovaginal pain is strikingly common and has a serious impact on women’s lives. Nevertheless, there are few longitudinal studies focusing on mechanisms involved in the pain development. One area of interest is how women cope with sexual activities and how this affects their pain. In this study, avoidance and endurance coping behaviors were explored as possible mediators of the relation between catastrophizing and pain, cross-sectionally and longitudinally.Methods251 women (18-35 years old) with vulvovaginal pain were recruited in university settings and filled out questionnaires about their pain, catastrophizing and coping behaviors at two occasions, with five months in between. Multiple mediation models were tested, exploring avoidance and endurance as mediators of the relation between catastrophizing and pain.ResultsThe results showed that avoidance was an influential mediator of the link between catastro¬phizing and pain. Using multiple mediation models we found that although the indirect effects of both avoidance and endurance were significant cross-sectionally, only avoidance was a significant mediator in the combined model exploring associations over time.ConclusionsThis study indicates that the strategies women with vulvovaginal pain use for coping with sexual activities are important for the course of pain. Avoidance and, to a lesser degree, endurance strate¬gies were identified as important mediators of the effects of catastrophizing on pain. When exploring the links over time, only avoidance emerged as a significant mediator.ImplicationsIn this longitudinal study, catastrophizing was linked to vulvovaginal pain, via avoidance and endurance of sexual activities. Hence, targeting catastrophizing early on in treatment, as well as addressing coping, may be important in clinical interventions.

scholarly journals Simulation of the microwave emission of multi-layered snowpacks using the Dense Media Radiative transfer theory: the DMRT-ML model

2013 ◽  
Vol 6 (4) ◽  
pp. 1061-1078 ◽  
Author(s):  
G. Picard ◽  
L. Brucker ◽  
A. Roy ◽  
F. Dupont ◽  
M. Fily ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Radiative Transfer ◽  
Thermal Emission ◽  
Remote Sensing Data ◽  
Microwave Emission ◽  
Alpine Regions ◽  
Wide Range ◽  
Dense Media ◽  
Wet Snow ◽  
Snow Conditions

Abstract. DMRT-ML is a physically based numerical model designed to compute the thermal microwave emission of a given snowpack. Its main application is the simulation of brightness temperatures at frequencies in the range 1–200 GHz similar to those acquired routinely by space-based microwave radiometers. The model is based on the Dense Media Radiative Transfer (DMRT) theory for the computation of the snow scattering and extinction coefficients and on the Discrete Ordinate Method (DISORT) to numerically solve the radiative transfer equation. The snowpack is modeled as a stack of multiple horizontal snow layers and an optional underlying interface representing the soil or the bottom ice. The model handles both dry and wet snow conditions. Such a general design allows the model to account for a wide range of snow conditions. Hitherto, the model has been used to simulate the thermal emission of the deep firn on ice sheets, shallow snowpacks overlying soil in Arctic and Alpine regions, and overlying ice on the large ice-sheet margins and glaciers. DMRT-ML has thus been validated in three very different conditions: Antarctica, Barnes Ice Cap (Canada) and Canadian tundra. It has been recently used in conjunction with inverse methods to retrieve snow grain size from remote sensing data. The model is written in Fortran90 and available to the snow remote sensing community as an open-source software. A convenient user interface is provided in Python.

scholarly journals Wind driven snow conditions control the occurrence of contemporary marginal mountain permafrost in the Chic-Chocs Mountains, south-eastern Canada – a case study from Mont Jacques-Cartier

2016 ◽  
Author(s):  
Gautier Davesne ◽  
Daniel Fortier ◽  
Florent Dominé ◽  
James T. Gray
Keyword(s):  
Surface Temperature ◽  
Snow Cover ◽  
Ground Surface ◽  
Climatic Conditions ◽  
Eastern Canada ◽  
Ground Surface Temperature ◽  
South Eastern ◽  
Snow Distribution ◽  
Snow Conditions ◽  
The Impact

Abstract. We present data from Mont Jacques-Cartier, the highest summit in the Appalachians of south-eastern Canada, to demonstrate that the occurrence of contemporary permafrost body is necessarily associated with a very thin and wind-packed winter snow cover which brings local azonal topo-climatic conditions on the dome-shaped summit. The aims of this study was (i) to understand the snow distribution pattern and snow thermo-physical properties on the Mont Jacques-Cartier summit; and (ii) to investigate the impact of snow on the spatial distribution of the ground surface temperature (GST) using temperature sensors deployed over the summit. Results showed that above the local treeline, the summit is characterized by snow cover typically less than 30 cm thick due to the physiography and surficial geomorphology of the site and the strong westerly winds. The mean annual ground surface temperature (MAGST) below this thin and wind-packed snow cover was about −1 °C in 2013 and 2014, for the higher exposed sector of the summit characterised by a block-field or sporadic herbaceous cover. In contrast, for the gentle slopes covered with stunted spruce (krummholz), and for the steep leeward slope to the SE of the summit the MAGST was around 3 °C in 2013 and 2014.

scholarly journals Subgrid parameterization of snow distribution at a Mediterranean site using terrestrial photography

2016 ◽  
Author(s):  
Rafael Pimentel ◽  
Javier Herrero ◽  
María José Polo
Keyword(s):  
Snow Cover ◽  
Snow Depth ◽  
Scale Effects ◽  
Control Area ◽  
Sigmoid Function ◽  
Snow Cover Fraction ◽  
Snow Distribution ◽  
Snow Model ◽  
Snow Conditions ◽  
High Level

Abstract. Subgrid variability introduces non-negligible scale effects on the GIS-based representation of snow. This heterogeneity is even more evident in semiarid regions, where the high variability of the climate produces various accumulation melting cycles throughout the year and a large spatial heterogeneity of the snow cover. This variability in a watershed can often be represented by snow depletion curves (DCs). In this study, terrestrial photography (TP) of a cell-sized area (30 x 30 m) was used to define local snow DCs at a Mediterranean site. Snow cover fraction (SCF) and snow depth (h) values obtained with this technique constituted the two datasets used to define DCs. A flexible sigmoid function was selected to parameterize snow behaviour on this subgrid scale. It was then fitted to meet five different snow patterns in the control area: one for the accumulation phase and four for the melting phase in a cycle within the snow season. Each pattern was successfully associated with the snow conditions and previous evolution. The resulting DCs were able to capture certain physical features of the snow, which were used in a decision-tree and included in the point snow model formulated by Herrero et al. (2009). The final performance of this model was tested against field observations recorded over four hydrological years (2009–2013). The calibration and validation of this DC-snow model was found to have a high level of accuracy with global RMSE values of 84.2 mm for the average snow depth and 0.18 m2 m-2 for the snow cover fraction in the control area. The use of DCs on the cell scale proposed in this research provided a sound basis for the extension of point snow models to larger areas by means of a gridded distributed calculation.

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