The Influence of Thermal Properties and Canopy- Intercepted Snow on Passive Microwave Transmissivity of a Scots Pine

While many microwave studies related to tree emission have been undertaken, a few have considered the effect of phenological change on the emission from coniferous trees. The permittivity of vegetation tissue is known to be influenced by water content, while the water content and phase is sensitive...

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Bibliographic Details
Published in:IEEE transactions on geoscience and remote sensing 2019-08, Vol.57 (8), p.5424-5433
Main Authors: Li, Qinghuan, Kelly, Richard, Leppanen, Leena, Vehvilainen, Juho, Kontu, Anna, Lemmetyinen, Juha, Pulliainen, Jouni
Format: Article
Language:English
Subjects:
Accumulation
Canopies
Canopy
Canopy-intercepted snow
Coniferous trees
Emission analysis
Emissivity
Forestry
Freezing
Microwave FET integrated circuits
Microwave measurement
Microwave radiometry
Moisture content
Radiometers
Skin
Skin temperature
Snow
Snow accumulation
Snow cover
Subzero temperature
Temperature
Temperature effects
Temperature measurement
Thermal properties
Thermodynamic properties
Tissue
Transmissivity
tree
Vegetation
Water content
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Summary:While many microwave studies related to tree emission have been undertaken, a few have considered the effect of phenological change on the emission from coniferous trees. The permittivity of vegetation tissue is known to be influenced by water content, while the water content and phase is sensitive to temperature in particular at temperatures below freezing. In addition to temperature, canopy-intercepted snow might also modify the tree emission and transmissivity in the microwave range. In this paper, a season-long experiment was designed to quantify the effect of snow accumulation and temperature on the observed microwave transmissivity from tree. A ground-based, upward-pointing multifrequency radiometer was used to monitor the microwave emissivity of a single coniferous tree at a site in Northern Finland. Radiometer measurements were combined with measurements of the canopy-intercepted snow cover and tree skin temperature. This paper presents two important findings. First, the tree transmissivity was strongly correlated with tree skin temperature under subzero temperature conditions, but uncorrelated with skin temperature changes above freezing. Second, although the tree transmissivity was slightly affected by the snow accumulation on the tree canopy, the overall influence on tree emission was statistically insignificant in this paper.
ISSN:0196-2892
1558-0644
DOI:10.1109/TGRS.2019.2899345