scholarly journals Soil dielectric characterization at L-band microwave frequencies during freeze-thaw transitions

2020 ◽  
Author(s):  
Alex Mavrovic ◽  
Renato Pardo Lara ◽  
Aaron Berg ◽  
François Demontoux ◽  
Alain Royer ◽  
...  
Keyword(s):  
Current Model ◽  
Freezing And Thawing ◽  
Microwave Frequencies ◽  
Dielectric Characterization ◽  
Freeze Thaw ◽  
L Band ◽  
Satellite Microwave ◽  
Permittivity Measurements ◽  
Microwave Permittivity

Abstract. Soil microwave permittivity is a crucial parameter in passive microwave retrieval algorithms but remains a challenging variable to measure. To validate and improve satellite microwave data products, precise and reliable estimations of the relative permittivity (ɛr = ɛ / ɛ0 = ɛ’ - jɛ’’; unitless) of soils are required, particularly for frozen soils. In this study, permittivity measurements were acquired using two different instruments: the newly designed open-ended coaxial probe (OECP) and the conventional Stevens HydraProbe. Both instruments were used to characterize the permittivity of soil samples undergoing several freeze/thaw cycles in a laboratory environment. The measurements were compared to soil permittivity models. We show that the OECP is a suitable device for measuring frozen (ɛ’frozen = [3.5;6.0], ɛ’’frozen = [0.4;1.2]) and thawed (ɛ’thawed = [6.5;22.8], ɛ’’thawed = [1.4;5.7]) soil microwave permittivity. We also demonstrate that cheaper and widespread soil permittivity probes operating at lower frequencies (i.e. Stevens HydraProbe) can be used to estimate microwave permittivity given proper calibration relative to an L-band (1–2 GHz) probe. This study also highlighted the need to improve dielectric soil models, particularly during freeze/thaw transitions. There are still important discrepancies between in situ and modelled estimates and no current model accounts for the hysteresis effect shown between freezing and thawing processes which could have a significant impact on freeze/thaw detection from satellites.

scholarly journals Soil dielectric characterization during freeze–thaw transitions using L-band coaxial and soil moisture probes

2021 ◽  
Vol 25 (3) ◽  
pp. 1117-1131
Author(s):  
Alex Mavrovic ◽  
Renato Pardo Lara ◽  
Aaron Berg ◽  
François Demontoux ◽  
Alain Royer ◽  
...  
Keyword(s):  
Current Model ◽  
Freezing And Thawing ◽  
Dielectric Characterization ◽  
Freeze Thaw ◽  
Thawing Processes ◽  
L Band ◽  
Satellite Microwave ◽  
Permittivity Measurements ◽  
Microwave Permittivity

Abstract. Soil microwave permittivity is a crucial parameter in passive microwave retrieval algorithms but remains a challenging variable to measure. To validate and improve satellite microwave data products, precise and reliable estimations of the relative permittivity (εr=ε/ε0=ε′-jε′′; unitless) of soils are required, particularly for frozen soils. In this study, permittivity measurements were acquired using two different instruments: the newly designed open-ended coaxial probe (OECP) and the conventional Stevens HydraProbe. Both instruments were used to characterize the permittivity of soil samples undergoing several freeze–thaw cycles in a laboratory environment. The measurements were compared to soil permittivity models. The OECP measured frozen (εfrozen′=[3.5; 6.0], εfrozen′′=[0.46; 1.2]) and thawed (εthawed′=[6.5; 22.8], εthawed′′=[1.43; 5.7]) soil microwave permittivity. We also demonstrate that cheaper and widespread soil permittivity probes operating at lower frequencies (i.e., Stevens HydraProbe) can be used to estimate microwave permittivity given proper calibration relative to an L-band (1–2 GHz) probe. This study also highlighted the need to improve dielectric soil models, particularly during freeze–thaw transitions. There are still important discrepancies between in situ and modeled estimates and no current model accounts for the hysteresis effect shown between freezing and thawing processes, which could have a significant impact on freeze–thaw detection from satellites.

scholarly journals Dielectric characterization of vegetation at L band using an open-ended coaxial probe

2018 ◽  
Vol 7 (3) ◽  
pp. 195-208 ◽  
Author(s):  
Alex Mavrovic ◽  
Alexandre Roy ◽  
Alain Royer ◽  
Bilal Filali ◽  
François Boone ◽  
...  
Keyword(s):  
Black Spruce ◽  
Microwave Remote Sensing ◽  
Dielectric Characterization ◽  
Sensing Applications ◽  
Remote Sensing Applications ◽  
L Band ◽  
Permittivity Measurements ◽  
Coaxial Probe

Abstract. Decoupling the integrated microwave signal originating from soil and vegetation remains a challenge for all microwave remote sensing applications. To improve satellite and airborne microwave data products in forest environments, a precise and reliable estimation of the relative permittivity (ε=ε′-iε′′) of trees is required. We developed an open-ended coaxial probe suitable for in situ permittivity measurements of tree trunks at L-band frequencies (1–2 GHz). The probe is characterized by uncertainty ratios under 3.3 % for a broad range of relative permittivities (unitless), [2–40] for ε′ and [0.1–20] for ε′′. We quantified the complex number describing the permittivity of seven different tree species in both frozen and thawed states: black spruce, larch, red spruce, balsam fir, red pine, aspen and black cherry. Permittivity variability is substantial and can range up to 300 % for certain species. Our results show that the permittivity of wood is linked to the freeze–thaw state of vegetation and that even short winter thaw events can lead to an increase in vegetation permittivity. The open-ended coaxial probe proved to be precise enough to capture the diurnal cycle of water storage inside the trunk for the length of the growing season.

scholarly journals Dielectric characterization of vegetation at L-band using an open-ended coaxial probe

2018 ◽  
Author(s):  
Alex Mavrovic ◽  
Alexandre Roy ◽  
Alain Royer ◽  
Filali Bilal ◽  
François Boone ◽  
...  
Keyword(s):  
Black Spruce ◽  
Microwave Remote Sensing ◽  
Dielectric Characterization ◽  
Sensing Applications ◽  
Remote Sensing Applications ◽  
L Band ◽  
Permittivity Measurements ◽  
Coaxial Probe

Abstract. Decoupling the integrated microwave signal originating from soil and vegetation remains a challenge for all microwave remote sensing applications. To improve satellite and airborne microwave data products in forest environments, a precise and reliable estimation of the relative permittivity (𝜺 = 𝜺’ – i 𝜺’’) of the trees is required. We developed an open-ended coaxial probe suitable for in situ permittivity measurements of tree trunks at L-band wavelengths (1–2 GHz). The probe is characterized by uncertainties under 3.3 % for a broad range of permittivities, [2–40] for 𝜺’ and [0.1–20] for 𝜺’’. We quantified the complex number describing the permittivity of seven different tree species in both frozen and thawed states: black spruce, larch, red spruce, balsam fir, red pine, aspen and black cherry. Variability in permittivity is substantial, and can range up to 300 % for some species. Our results show that the permittivity of wood is linked to the freeze/thaw state of the vegetation and that even short winter thaw events lead to an increase in vegetation permittivity. The open-ended coaxial probe proved to be precise enough to capture the diurnal cycle of water storage inside the trunk over the growing season.

Non-intrusive in-situ permittivity measurements dedicated to the development of a P and L band dielectric model of wood

2021 ◽  
Author(s):  
F. Demontoux ◽  
M. Gati ◽  
M. el Boudali ◽  
L. Villard ◽  
JP Wigneron ◽  
...  
Keyword(s):  
Dielectric Model ◽  
L Band ◽  
Permittivity Measurements

scholarly journals Northern Hemisphere Surface Freeze/Thaw Product from Aquarius L-band Radiometers

2018 ◽  
Author(s):  
Michael Prince ◽  
Alexandre Roy ◽  
Ludovic Brucker ◽  
Alain Royer ◽  
Youngwook Kim ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Earth Science ◽  
Surface Air Temperature ◽  
Freezing And Thawing ◽  
Science Data ◽  
Freeze Thaw ◽  
Open Land ◽  
Hemisphere Surface ◽  
L Band ◽  
Earth Science Data

Abstract. In the Northern Hemisphere, seasonal changes in surface freeze/thaw (FT) cycle are an important component of surface energy, hydrological and eco-biogeochemical processes that must be accurately monitored. This paper presents the weekly polar-gridded Aquarius passive L-Band surface freeze/thaw product (FT-AP) distributed on the Equal-Area Scalable Earth Grid version 2.0, above the parallel 50° N, with a spatial resolution of 36 km x 36 km. The FT-AP classification algorithm is based on a seasonal threshold approach using the normalized polarization ration, references for frozen and thawed conditions and optimized thresholds. To evaluate the uncertainties of the product, we compared it with another satellite FT product also derived from passive microwave observations but at higher frequency: the resampled 37 GHz FT Earth Science Data Record (FT-ESDR). The assessment was carried out during the overlapping period between 2011 and 2014. Results show that 77.1 % of their common grid cells have an agreement better than 80 %. Their differences vary with land cover type (tundra, forest and open land) and freezing and thawing periods. The best agreement is obtained during the thawing transition and over forest areas, with differences between product mean freeze or thaw onsets of under 0.4 weeks. Over tundra, FT-AP tends to detect freeze onset 2–5 weeks earlier than FT-ESDR, likely due to FT sensitivity to the different frequencies used. Analysis with mean surface air temperature time series from six in situ meteorological stations shows that the main discrepancies between FT-AP and FT-ESDR are related to false frozen retrievals in summer for some regions with FT-AP. The Aquarius product is distributed by the U.S. National Snow and Ice Data Center (NSIDC) at https://nsidc.org/data/nsidc-0736/versions/1 with the doi:10.5067/OV4R18NL3BQR.

scholarly journals Evaluation of MERRA Land Surface Estimates in Preparation for the Soil Moisture Active Passive Mission

2011 ◽  
Vol 24 (15) ◽  
pp. 3797-3816 ◽  
Author(s):  
Yonghong Yi ◽  
John S. Kimball ◽  
Lucas A. Jones ◽  
Rolf H. Reichle ◽  
Kyle C. McDonald
Keyword(s):  
Soil Moisture ◽  
Land Surface ◽  
Surface Soil ◽  
Middle Latitude ◽  
Surface Soil Moisture ◽  
Freeze Thaw ◽  
Earth Observing System ◽  
In Situ Observations ◽  
Satellite Microwave

Abstract The authors evaluated several land surface variables from the Modern-Era Retrospective Analysis for Research and Applications (MERRA) product that are important for global ecological and hydrological studies, including daily maximum (Tmax) and minimum (Tmin) surface air temperatures, atmosphere vapor pressure deficit (VPD), incident solar radiation (SWrad), and surface soil moisture. The MERRA results were evaluated against in situ measurements, similar global products derived from satellite microwave [the Advanced Microwave Scanning Radiometer for Earth Observing System (EOS) (AMSR-E)] remote sensing and earlier generation atmospheric analysis [Goddard Earth Observing System version 4 (GEOS-4)] products. Relative to GEOS-4, MERRA is generally warmer (~0.5°C for Tmin and Tmax) and drier (~50 Pa for VPD) for low- and middle-latitude regions (<50°N) associated with reduced cloudiness and increased SWrad. MERRA and AMSR-E temperatures show relatively large differences (>3°C) in mountainous areas, tropical forest, and desert regions. Surface soil moisture estimates from MERRA (0–2-cm depth) and two AMSR-E products (~0–1-cm depth) are moderately correlated (R ~ 0.4) for middle-latitude regions with low to moderate vegetation biomass. The MERRA derived surface soil moisture also corresponds favorably with in situ observations (R = 0.53 ± 0.01, p < 0.001) in the midlatitudes, where its accuracy is directly proportional to the quality of MERRA precipitation. In the high latitudes, MERRA shows inconsistent soil moisture seasonal dynamics relative to in situ observations. The study’s results suggest that satellite microwave remote sensing may contribute to improved reanalysis accuracy where surface meteorological observations are sparse and in cold land regions subject to seasonal freeze–thaw transitions. The upcoming NASA Soil Moisture Active Passive (SMAP) mission is expected to improve MERRA-type reanalysis accuracy by providing accurate global mapping of freeze–thaw state and surface soil moisture with 2–3-day temporal fidelity and enhanced (≤9 km) spatial resolution.

scholarly journals Northern Hemisphere surface freeze–thaw product from Aquarius L-band radiometers

2018 ◽  
Vol 10 (4) ◽  
pp. 2055-2067 ◽  
Author(s):  
Michael Prince ◽  
Alexandre Roy ◽  
Ludovic Brucker ◽  
Alain Royer ◽  
Youngwook Kim ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Earth Science ◽  
Surface Air Temperature ◽  
Freezing And Thawing ◽  
Science Data ◽  
Freeze Thaw ◽  
Open Land ◽  
Hemisphere Surface ◽  
L Band ◽  
Earth Science Data

Abstract. In the Northern Hemisphere, seasonal changes in surface freeze–thaw (FT) cycles are an important component of surface energy, hydrological and eco-biogeochemical processes that must be accurately monitored. This paper presents the weekly polar-gridded Aquarius passive L-band surface freeze–thaw product (FT-AP) distributed on the Equal-Area Scalable Earth Grid version 2.0, above the parallel 50° N, with a spatial resolution of 36 km  ×  36 km. The FT-AP classification algorithm is based on a seasonal threshold approach using the normalized polarization ratio, references for frozen and thawed conditions and optimized thresholds. To evaluate the uncertainties of the product, we compared it with another satellite FT product also derived from passive microwave observations but at higher frequency: the resampled 37 GHz FT Earth Science Data Record (FT-ESDR). The assessment was carried out during the overlapping period between 2011 and 2014. Results show that 77.1 % of their common grid cells have an agreement better than 80 %. Their differences vary with land cover type (tundra, forest and open land) and freezing and thawing periods. The best agreement is obtained during the thawing transition and over forest areas, with differences between product mean freeze or thaw onsets of under 0.4 weeks. Over tundra, FT-AP tends to detect freeze onset 2–5 weeks earlier than FT-ESDR, likely due to FT sensitivity to the different frequencies used. Analysis with mean surface air temperature time series from six in situ meteorological stations shows that the main discrepancies between FT-AP and FT-ESDR are related to false frozen retrievals in summer for some regions with FT-AP. The Aquarius product is distributed by the U.S. National Snow and Ice Data Center (NSIDC) at https://nsidc.org/data/aq3_ft/versions/5 with the DOI https://doi.org/10.5067/OV4R18NL3BQR.

Fabrication and characterization of in-situ grown epitaxial Ba1-xSrxTiO3 composition spreads

2001 ◽  
Vol 700 ◽  
Author(s):  
K. S. Chang ◽  
M. Aronova ◽  
O. Famodu ◽  
J. Hattrick-Simpers ◽  
S. E. Lofland ◽  
...  
Keyword(s):  
Pulsed Laser ◽  
Frequency Dispersion ◽  
Laser Deposition ◽  
Microwave Frequencies ◽  
Dielectric Characterization ◽  
Microwave Microscopy ◽  
Fabrication And Characterization ◽  
Multi Mode

AbstractWe have used our combinatorial pulsed laser deposition system to in-situ fabricate epitaxial Ba1-xSrxTiO3 thin film composition spreads on (100) LaAlO3 substrates. Multimode quantitative microwave microscopy was used to perform dielectric characterization of the spreads at multiple microwave frequencies simultaneously. Systematic variation in dielectric properties as a function of composition is studied. The multi-mode measurements allow frequency dispersion studies. We observe strong composition-dependent dielectric dispersion in Ba1-xSrxTiO3.

scholarly journals Stability Evaluation of Volcanic Slope Subjected to Rainfall and Freeze-Thaw Action Based on Field Monitoring

2011 ◽  
Vol 2011 ◽  
pp. 1-14 ◽  
Author(s):  
Shima Kawamura ◽  
Seiichi Miura
Keyword(s):  
Soil Moisture ◽  
Prediction Method ◽  
Field Studies ◽  
Stability Evaluation ◽  
Freezing And Thawing ◽  
Freeze Thaw ◽  
In Situ Data ◽  
Failure Conditions ◽  
Cut Slopes

Rainfall-induced failures of natural and artificial slopes such as cut slopes, which are subjected to freezing and thawing, have been frequently reported in Hokkaido, Japan. In particular, many failures occur intensively from spring to summer seasons. Despite numerous field studies, explanation of their mechanical behavior based on in situ data has not yet been completely achieved due to the difficulty in grasping failure conditions. This study aims at clarifying the aspects of in-situ volcanic slopes subjected to rainfall and freeze-thaw action. The changes in soil moisture, pore pressure, deformations, and temperatures in the slope were investigated using soil moisture meters, tensiometers, thermocouple sensors, clinometers, settlement gauges, an anemovane, a snow gauge, and a rainfall gauge. The data generated from these measures indicated deformation in the slope examined mainly proceeded during the drainage process according to changes in soil moisture. Based on this data, a prediction method for failures is discussed in detail.

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