Melody Sandells

Melody Sandells
Northumbria University · Department of Geography and Environment

PhD

About

48
Publications
17,730
Reads
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992
Citations
Additional affiliations
August 2015 - March 2016
CORES Science and Engineering Limited
Position
  • Managing Director

Publications

Publications (48)
Preprint
The European Space Agency SnowSAR instrument is a side looking, dual polarized (VV/VH), X/Ku band synthetic aperture radar (SAR), operable from a small aircraft. Between 2010 and 2013, the instrument was deployed at several sites in Northern Finland, Austrian Alps, and northern Canada. The purpose of the airborne campaigns was to measure the backsc...
Preprint
Full-text available
Snowpack microstructure controls the transfer of heat to, and the temperature of, the underlying soils. In situ measurements of snow and soil properties from four field campaigns during two different winters (March and November 2018, January and March 2019) were compared to an ensemble of CLM5.0 (Community Land Model) simulations, at Trail Valley C...
Preprint
Full-text available
Seasonal snow cover is the largest single component of the cryosphere in areal extent, covering an average of 46 million square km of Earth's surface (31 % of the land area) each year, and is thus an important expression of and driver of the Earth’s climate. In recent years, Northern Hemisphere spring snow cover has been declining at about the same...
Article
Within the framework of European Space Agency (ESA) activities, several campaigns were carried out in the last decade with the purpose of exploiting the capabilities of multifrequency synthetic aperture radar (SAR) data to retrieve snow information. This article presents the results obtained from the ESA SnowSAR airborne campaigns, carried out betw...
Article
Full-text available
The modular Snow Microwave Radiative Transfer (SMRT) model simulates microwave scattering behavior in snow via different selectable theories and snow microstructure representations, which is well suited to intercomparisons analyses. Here, five microstructure models were parameterized from X-ray tomography and thin-section images of snow samples and...
Article
Full-text available
The Snow Ensemble Uncertainty Project (SEUP) is an effort to establish a baseline characterization of snow water equivalent (SWE) uncertainty across North America with the goal of informing global snow observational needs. An ensemble-based modeling approach, encompassing a suite of current operational models is used to assess the uncertainty in SW...
Preprint
Full-text available
The Snow Ensemble Uncertainty Project (SEUP) is an effort to establish a baseline characterization of snow water equivalent (SWE) uncertainty across North America with the goal of informing global snow observational needs. An ensemble-based modeling approach, encompassing a suite of current operational models, is used to assess the uncertainty in S...
Article
Full-text available
Spatial variability in snowpack properties negatively impacts our capacity to make direct measurements of snow water equivalent (SWE) using satellites. A comprehensive data set of snow microstructure (94 profiles at 36 sites) and snow layer thickness (9000 vertical profiles across nine trenches) collected over two winters at Trail Valley Creek, NWT...
Article
Full-text available
In this study, snow slab data collected from the Arc-tic Snow Microstructure Experiment were used in conjunction with a six-directional flux coefficient model to calculate individual slab absorption and scattering coefficients. These coefficients formed the basis for a new semiempirical extinction coefficient model, using both frequency and optical...
Article
Full-text available
Spatial variability in snowpack properties negatively impacts our capacity to make direct measurements of snow water equivalent (SWE) using satellites. A comprehensive data set of snow microstructure (94 profiles at 36 sites) and snow layer thickness (9000 vertical profiles across 9 trenches) collected over two winters at Trail Valley Creek, NWT, C...
Article
Full-text available
This paper is the outcome of a community initiative to identify major unsolved scientific problems in hydrology motivated by a need for stronger harmonisation of research efforts. The procedure involved a public consultation through on-line media, followed by two workshops through which a large number of potential science questions were collated, p...
Article
Full-text available
The Snow Microwave Radiative Transfer (SMRT) thermal emission and backscatter model was developed to determine uncertainties in forward modeling through intercomparison of different model ingredients. The model differs from established models by the high degree of flexibility in switching between different electromagnetic theories, representations...
Article
Full-text available
The Snow Microwave Radiative Transfer (SMRT) thermal emission and backscatter model was developed to determine uncertainties in forward modeling through intercomparison of different model ingredients. The model differs from established models by the high degree of flexibility in switching between different electromagnetic theories, representations...
Article
Full-text available
This is the first study to encompass a wide range of coupled snow evolution and microwave emission models in a common modelling framework in order to generalise the link between snowpack microstructure predicted by the snow evolution models and microstructure required to reproduce observations of brightness temperature as simulated by snow emission...
Article
Full-text available
The microstructure and density of ice layers in snowpacks is poorly quantified. Here we present a new field method for measuring the density of ice layers caused by melt or rain-on-snow events. The method was used on 87 ice layer samples taken from natural and artificial ice layers in the Canadian Arctic and mid-latitudes. Mean measured ice layer d...
Article
Full-text available
This is the first study to encompass a wide range of coupled snow evolution and microwave emission models in a common modelling framework in order to generalise the link between snowpack microstructure predicted by the snow evolution models and microstructure required to reproduce observations of brightness temperature as simulated by snow emission...
Article
Full-text available
The Arctic Snow Microstructure Experiment (ASMEx) took place in Sodankylä, Finland in the winters of 2013-2014 and 2014-2015. Radiometric, macro-, and microstructure measurements were made under different experimental conditions of homogenous snow slabs, extracted from the natural seasonal taiga snowpack. Traditional and modern measurement techniqu...
Article
Full-text available
The Arctic Snow Microstructure Experiment (ASMEx) took place in Sodankylä, Finland in the winters of 2013–2014 and 2014–2015. Radiometric, macro-, and microstructure measurements were made under different experimental conditions of homogenous snow slabs, extracted from the natural seasonal taiga snowpack. Traditional and modern measurement techniqu...
Article
Full-text available
Microwave emission models are a critical component of snow water equivalent retrieval algorithms applied to passive microwave measurements. Several such emission models exist, but their differences need to be systematically compared. This paper compares the basic theories of two models: the multiple-layer Helsinki University of Technology (HUT) mod...
Article
Full-text available
Ice layers in snowpacks introduce uncertainty in satellite derived estimates of snow water equivalent, have ecological impacts on plants and animals, and change the thermal and vapour transport properties of the snowpack. The microstructure and specifically the density of ice layers is poorly quantified. Here we present a new field method, for meas...
Article
Scientists from the snow and soil remote sensing communities met to build on recent developments in objective snow microstructure measurement techniques by improving the understanding of their application in remote sensing at microwave frequencies.
Article
measurements of snowpack properties (stratigraphic layering, density, grain size, and temperature) were used as inputs to the multilayer Helsinki University of Technology (HUT) microwave emission model at a centimeter-scale horizontal resolution, across a 4.5 m transect of ground-based passive microwave radiometer footprints near Churchill, Manitob...
Article
Full-text available
It is not yet possible to determine whether global snow mass has changed over time despite collection of passive microwave data for more than thirty years. Physically-based, but computationally fast snow and soil models have been coupled to form the basis of a data assimilation system for retrievals of snow mass and soil moisture from existing and...
Article
Changes in snow climatology can be quantified through interpretation of over 40 years of remote sensing data. Snow mass retrievals from passive microwave radiometry have large errors associated with them from uncertainties in the snow grain size and other snow properties. More accurate knowledge of the snow grain size may lead to improved estimates...
Presentation
Passive microwave observations have been used for over 30 years to gain information on snow mass on a global scale. Original algorithms to retrieve snow mass were necessarily simple because of the computational limitations of the era, but the simplifying assumptions of constant and uniform snow properties have been shown to result in significant er...
Conference Paper
Full-text available
Remote sensing is the only practicable means to observe snow at large scales. Measurements from passive microwave instruments have been used to derive snow climatology since the late 1970’s, but the algorithms used were limited by the computational power of the era. Simplifications such as the assumption of constant snow properties enabled snow mas...
Article
In mountainous and cold regions of the world snowmelt dominates the water balance, yet is quantified poorly despite the wealth of available remote sensing observations. Field measurements of snow cover and soil moisture are limited to experimental sites while the accuracy of soil moisture measurements from passive and active microwave sensors such...
Article
Full-text available
Thirty‐three snowpack models of varying complexity and purpose were evaluated across a wide range of hydrometeorological and forest canopy conditions at five Northern Hemisphere locations, for up to two winter snow seasons. Modeled estimates of snow water equivalent (SWE) or depth were compared to observations at forest and open sites at each locat...
Article
Comparisons between the climatology derived from global models and from around 30 years of passive microwave observations indicate large discrepancies in snow water equivalent, particularly in Siberia, so there is a need to understand the errors in both observations and models in order to account for the difference. The algorithm used to derive the...
Article
Soil moisture is an important component of the water cycle and will be measured for the first time on a global scale by a dedicated passive L-band microwave radiometer that is planned for launch in 2008. Here, the contribution of topography to the error budget is examined for a vegetated scene with uniform microwave emission. Dual-polarization brig...
Article
The s–x model of microwave emission from soil and vegetation layers is widely used to estimate soil moisture content from passive microwave observations. Its application to prospective satellite-based observations aggregating several thousand square kilometres requires understanding of the effects of scene heterogeneity. The effects of heterogeneit...
Article
At the interface between the land surface and atmosphere, soil moisture governs evapotranspiration, infiltration and runoff processes. Current knowledge of the soil moisture is poor, although a satellite L-band passive microwave mission is planned that will monitor the global surface soil moisture. This Soil Moisture and Ocean Salinity (SMOS) missi...
Article
Models of snow processes in areas of possible large-scale change need to be site independent and physically based. Here, the accumulation and ablation of the seasonal snow cover beneath a fir canopy has been simulated with a new physically based snow–soil vegetation–atmosphere transfer scheme (Snow-SVAT) called SNOWCAN. The model was formulated by...
Article
A new snow-soil-vegetation-atmosphere transfer (Snow-SVAT) scheme, which simulates the accumulation and ablation of the snow cover beneath a forest canopy, is presented. The model was formulated by coupling a canopy optical and thermal radiation model to a physically-based multi-layer snow model. This canopy radiation model is physically-based yet...
Article
Numerical simulation of snowcover dynamics in mountain environments is complicated by the fact that forest canopies strongly affect the snow surface energy balance relative to open sites. A number of methods to simulate the affect of forest canopies on the snow surface microclimate have recently been developed and successfully applied across a rang...
Article
Prediction of meltwater runoff is crucial to communities where the seasonal snowpack is the major water supply. Water is itself a vital resource and it carries nutrients both in solution and in suspension. Simulation of snowpack depletion at a point in open areas has previously been shown to produce accurate results using physically based models su...
Article
Physically based snow models use different approaches to simulate the development and melting of the snowcover. Two such models, the two-layer grid-based model SNOBAL and the more complex model SNOWCAN are used to simulate the snowcover over an experimental headwater catchment within the Reynolds Creek Experimental Watershed in the Owhyee mountains...

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