Temperature effects on L-band vegetation optical depth of a boreal forest

REMOTE SENSING OF ENVIRONMENT

卷:263

Article

Schwank, Mike^1,2  Kontu, Anna³  Mialon, Arnaud⁵  Naderpour, Reza¹  Houtz, Derek^1,6  Lemmetyinen, Juha⁴  Rautiainen, Kimmo⁴  Li, Qinghuan⁷  Richaume, Philippe⁵  Kerr, Yann⁵  Maetzler, Christian² 

[1] Fed Res Inst Forrest Snow & Landscape Res WSL, Zurcherstr 111, CH-8903 Birmensdorf, Switzerland

[2] GAMMA Remote Sensing Res & Consulting AG, Worbstr 225, CH-3073 Gumlingen, Switzerland

[3] Finnish Meteorol Inst, Arctic Space Ctr, Tahtelantie 62, Sodankyla 99600, Finland

[4] Finnish Meteorol Inst, Earth Observat Res, POB 503, Helsinki 00101, Finland

[5] Ctr Study Biosphere Space, 18 Ave Edouard Belin, F-31401 Toulouse 9, France

[6] TerraRad Tech AG, Freilagerstr 97, CH-8047 Zurich, Switzerland

[7] Chinese Acad Sci, Aerosp Informat Res Inst, Key Lab Digital Earth Sci, Beijing, Peoples R China

关键词: Close-range L-band radiometry;    Microwave remote sensing;    Vegetation Optical Depth (VOD);    Two-stream Emission Model (2S EM);    Ground permittivity;    SMOS;    SMAP;    Boreal forest;   

DOI  :  10.1016/j.rse.2021.112542

来源: Elsevier

【 摘 要 】

ElectroMagnetic (EM) reasons resulting in temperature dependence of L-band Vegetation Optical Depth (L-VOD) are currently overlooked in remote sensing products. Discrepancies in retrievals of geophysical surface properties over vegetated areas can result from this incompleteness. This perception motivated to explore EM considerations in how temperature drives L-VOD of a boreal forest. Thereto, a novel physics-based model is developed and evaluated to assess L-VOD sensitivities to canopy temperature and some other model parameters. The L-VOD model is compared to L-VOD derived from close-range L-band brightness temperatures measured through the tree canopy at the Finnish Meteorological Institute's Arctic Research Center (FMI-ARC) in Sodankyla center dot (Finland) during a 4-week and a 1-day period in 2019. Furthermore, the model's ability to explain L-VOD retrieved from brightness temperatures of the Soil Moisture and Ocean Salinity (SMOS) satellite over the Sodankyla center dot grid cell is investigated. Experimental L-VOD are maximal at around 0 degrees C and decrease when canopy temperature is moving away from zero degree Celsius. This temperature response, observed at different temporal- and spatial scales, is captured by the proposed L-VOD model and explained by freezing tree sap-water and the dependence of water permittivity on temperature. The demonstrated EM-induced temperature dependence suggest caution with interpreting satellite-based L-VOD, because increased L-VOD around the freezing point is not solely due to increased biomass or rehydration of the vegetation. Further, our study can find future application to compensate L-VOD for EM-induced temperature sensitivity. This potentially leads to improved explanatory power of temperature normalized L-VOD for characterization of forest phenology. Furthermore, we suggest examining the presence and strength of the demonstrated L-VOD temperature response as a practical L-VOD retrieval quality assessment method under steady forest phenology.

【 授权许可】

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