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Geoscientific Instrumentation, Methods and Data Systems An interactive open-access journal of the European Geosciences Union
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Volume 7, issue 3 | Copyright
Geosci. Instrum. Method. Data Syst., 7, 195-208, 2018
https://doi.org/10.5194/gi-7-195-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 11 Jul 2018

Research article | 11 Jul 2018

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

Alex Mavrovic1,2, Alexandre Roy1,2,3,6, Alain Royer1,2, Bilal Filali4, François Boone5, Christoforos Pappas2,6, and Oliver Sonnentag2,6 Alex Mavrovic et al.
  • 1Centre d'Applications et de Recherches en Télédétection, Université de Sherbrooke, Sherbrooke, Québec, J1K 2R1, Canada
  • 2Centre d'Études Nordiques, Université Laval, Québec, Québec, G1V 0A6, Canada
  • 3Département des Sciences de l'Environnement, Université du Québec à Trois-Rivières (UQTR), Trois-Rivières, Québec, G9A 5H7, Canada
  • 4Terraprobe Geoscience Corp., Vancouver, British Columbia, V3K 6X7, Canada
  • 5Centre de Recherche en Nanofabrication et en Nanocaractérisation, Université de Sherbrooke, Sherbrooke, Québec, J1K 2R1, Canada
  • 6Département de géographie, Université de Montréal, Montréal, Québec, H2V 2B8, Canada

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 (1–2GHz). 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.

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To improve microwave satellite and airborne observation products in forest environments, a precise and reliable estimation of the permittivity of trees is required. We developed a probe suitable to measure the permittivity of tree trunks at L band in the field. The system is easily transportable in the field, low energy consuming, operational at low temperatures and weatherproof. The permittivity of seven tree species in both frozen and thawed states was measured, showing important contrast.
To improve microwave satellite and airborne observation products in forest environments, a...
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