Application of a plane-stratified emission model to predict the effects of vegetation in passive microwave radiometry

Khil ha Le, R. Chawn Harlow, Eleanor J. Burke, W. James Shuttleworth

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

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.

Original languageEnglish (US)
Pages (from-to)139-151
Number of pages13
JournalHydrology and Earth System Sciences
Volume6
Issue number2
StatePublished - 2002

Fingerprint

canopy
vegetation
permittivity
brightness temperature
oscillation
electromagnetic radiation
microwave
effect
air
parameter
dry matter
vertical distribution
water content
temperature

Keywords

  • Passive microwave
  • Retrieval
  • SMOS
  • Soil moisture
  • Vegetation

ASJC Scopus subject areas

  • Earth and Planetary Sciences (miscellaneous)
  • Water Science and Technology

Cite this

Application of a plane-stratified emission model to predict the effects of vegetation in passive microwave radiometry. / Le, Khil ha; Harlow, R. Chawn; Burke, Eleanor J.; Shuttleworth, W. James.

In: Hydrology and Earth System Sciences, Vol. 6, No. 2, 2002, p. 139-151.

Research output: Contribution to journalArticle

@article{40c60b50ef6040289cb90b98a1b53b2d,
title = "Application of a plane-stratified emission model to predict the effects of vegetation in passive microwave radiometry",
abstract = "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, Retrieval, SMOS, Soil moisture, Vegetation",
author = "Le, {Khil ha} and Harlow, {R. Chawn} and Burke, {Eleanor J.} and Shuttleworth, {W. James}",
year = "2002",
language = "English (US)",
volume = "6",
pages = "139--151",
journal = "Hydrology and Earth System Sciences",
issn = "1027-5606",
publisher = "European Geosciences Union",
number = "2",

}

TY - JOUR

T1 - Application of a plane-stratified emission model to predict the effects of vegetation in passive microwave radiometry

AU - Le, Khil ha

AU - Harlow, R. Chawn

AU - Burke, Eleanor J.

AU - Shuttleworth, W. James

PY - 2002

Y1 - 2002

N2 - 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.

AB - 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.

KW - Passive microwave

KW - Retrieval

KW - SMOS

KW - Soil moisture

KW - Vegetation

UR - http://www.scopus.com/inward/record.url?scp=0036304924&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0036304924&partnerID=8YFLogxK

M3 - Article

AN - SCOPUS:0036304924

VL - 6

SP - 139

EP - 151

JO - Hydrology and Earth System Sciences

JF - Hydrology and Earth System Sciences

SN - 1027-5606

IS - 2

ER -