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| Titel |
Application of a plane-stratified emission model to predict the effects of vegetation in passive microwave radiometry |
| VerfasserIn |
K. Lee, R. Chawn Harlow, E. J. Burke, W. J. Shuttleworth |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1027-5606
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| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 6, no. 2 ; Nr. 6, no. 2, S.139-152 |
| Datensatznummer |
250003450
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| Publikation (Nr.) |
 copernicus.org/hess-6-139-2002.pdf |
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| Zusammenfassung |
| This paper reports the
application to vegetation canopies of a coherent model for the propagation of
electromagnetic radiation through a stratified medium. The resulting multi-layer
vegetation model is plausibly realistic in that it recognises the dielectric
permittivity of the vegetation matter, the mixing of the dielectric
permittivities for vegetation and air within the canopy and, in simplified
terms, the overall vertical distribution of dielectric permittivity and
temperature through the canopy. Any sharp changes in the dielectric profile of
the canopy resulted in interference effects manifested as oscillations in the
microwave brightness temperature as a function of canopy height or look angle.
However, when Gaussian broadening of the top and bottom of the canopy
(reflecting the natural variability between plants) was included within the
model, these oscillations were eliminated. The model parameters required to
specify the dielectric profile within the canopy, particularly the parameters
that quantify the dielectric mixing between vegetation and air in the canopy,
are not usually available in typical field experiments. Thus, the feasibility of
specifying these parameters using an advanced single-criterion,
multiple-parameter optimisation technique was investigated by automatically
minimizing the difference between the modelled and measured brightness
temperatures. The results imply that the mixing parameters can be so determined
but only if other parameters that specify vegetation dry matter and water
content are measured independently. The new model was then applied to
investigate the sensitivity of microwave emission to specific vegetation
parameters.
Keywords: passive microwave, soil moisture, vegetation, SMOS, retrieval |
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