Thermal IR exitance model of a plant canopy

Kimes, D. S.; Smith, James A.; Link, Lewis E.

doi:10.1364/ao.20.000623

Cited by 43 publications

(10 citation statements)

References 19 publications

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“…A variety of terminology has been used to describe LST. For example, when environmental downwelling thermal radiance is of concern, terms such as "effective radiant temperature" and "effective brightness temperature" have been used (e.g., [1], [20]). A related variable that is very difficult to measure from remote sensing is the surface "aerodynamic temperature," which is the temperature of the surface at the effective level of sensible heat exchange.…”

Section: A Planck Law and Emissivitymentioning

confidence: 99%

“…For nonisothermal surfaces, the Kimes-Smith-Link model may be used to compute directional emission [20]. This model employs a pure geometric-optical (GO) approach to interpret directional thermal emission.…”

Section: Models For Directional Thermal Emissionmentioning

confidence: 99%

“…Kimes et al [20], for example, showed that the effective radiant temperature of a three-layer canopy may exhibit differences of 2 K as view zenith angles vary from near horizontal to near nadir. Similarly, Dozier and Warren [12] showed that the directional emissivity of snow surfaces may produce as much as 3 K angular variation in brightness temperature.…”

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confidence: 99%

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A conceptual model for effective directional emissivity from nonisothermal surfaces

Strahler

Friedl

1999

IEEE Trans. Geosci. Remote Sensing

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The conventional definition of emissivity requires the source of radiation to be isothermal in order to compare its thermal emission to that of a blackbody at the same temperature. This requirement is not met for most land surfaces considered in thermal infrared remote sensing. Thus, the effective or equivalent emissivity of nonisothermal surfaces has been a poorly defined but widely used concept for years. Recently, several authors have attempted to define this concept more clearly. Unfortunately, definitions such as ensemble emissivity (e-emissivity) and emissivity derived from the surface bidirectional reflectance distribution function (r-emissivity) [27] do not fully satisfy current needs for estimating true land surface temperature (LST). We suggest the use of an additional term, the "apparent emissivity increment," which considers the effects of geometric optics to explain the directional and spectral dependence in LST caused by the three-dimensional (3-D) structure and subpixel temperature distribution of the surface. We define this quantity based upon the emissivity derived from the bidirectional reflectance distribution function (" " " BRDF ) for isothermal surfaces and present a conceptual model of thermal emission from nonisothermal land surfaces. Our study also indicates that an average LST corresponding to the hemispherical wideband " " " BRDF will be useful in remote sensing-based LST modeling and inversion.Index Terms-BRDF, brightness temperature, emmisivity, geometric optics, land surface temperature.

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Section: A Planck Law and Emissivitymentioning

confidence: 99%

Section: Models For Directional Thermal Emissionmentioning

confidence: 99%

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A conceptual model for effective directional emissivity from nonisothermal surfaces

Strahler

Friedl

1999

IEEE Trans. Geosci. Remote Sensing

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“…Although surface temperature has been widely used, its interpretation is a difficult task because of the complexity and heterogeneity of land surface [1]. To make a better use of thermal infrared remotely-sensed data and infer foliage and soil component temperatures with thermal infrared measurements based on extensive understanding of canopy directional thermal radiative features, a large of study has been devoted to quantitatively simulate directional effects in thermal infrared of vegetative canopy [2]- [6].…”

Section: Introductionmentioning

confidence: 99%

Simulation of Directional Emission from Vegetative Canopy using Monte-Carlo Method

Wang

2006

2006 IEEE International Symposium on Geoscience and Remote Sensing

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Although directional measurements of brightness temperature has made by a number of satellitebased and airborne sensors for a long time, interpretation of such measurements is a difficult task due to the fact that surface radiometric temperatures are resulted from energy balances in multi-scales from leaf and soil to the top of canopy or pixel. In this paper, a non-isothermal Monte-Carlo method based algorithm was proposed to model the angular emission from vegetative canopy and scale radiometric temperatures of foliage and soil to the top of canopy. This approach allows an accurate simulation of multi-reflection between foliage layers, foliage layer and soil surface, and foliage layers and sky, as well as the non-isothermal condition within canopy and between canopy layers and soil surface. Field measurements of directional thermal infrared radiation, which were collected in the Shunyi remote sensing campaign in Shunyi, Beijing in 2001 was used to preliminarily validate this non-isothermal Monte-Carlo algorithm. A reasonable agreement was archived from this validation.

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“…Several mathematical models have been developed which predict the directional sensor response as a function of canopy structure, optical and/or thermal properties of the leaves and atmospheric radiance properties, as well as environmental conditions in the case of thermal IR models (Suits 1972, Smith and Oliver 1974, Kimes et al 1981). These models serve as tools for interpreting sensor response data from vegetation canopies and for extracting information about Downloaded by [University of Calgary] at 19:04 04 February 2015…”

Section: Introductionmentioning

confidence: 99%

Diurnal variations of vegetation canopy structure

Kimes

Kirchner

1983

International Journal of Remote Sensing

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The leaf inclination-azimuth angle distribution is a major determinant of the electromagnetic response of vegetation canopies. In field and modelling studies, researcherscommonly assume that (i) leaf orientation can be described by two separate distributions of inclination and azimuth angles, (ii) the leaf inclination angle distribution of a particular vegetation type and growth stage is diurnally static and (iii) the leaf azimuth angle distribution is symmetric. In this study the three-dimensional orientation of leaves described as a leaf inclination-azimuth angle distribution plotted in polar co-ordinates was measured throughout a day for a cotton and a soybean canopy. The results and the literature review showed that this distribution can vary significantly on a diurnal basis due to vegetation type, heliotropic leaf movement, environmental conditions (e.g. wind) and vegetation stress (e.g. water stress). The study also showed that it is erroneous to treat two separate distributions of azimuth and inclination angles rather than one three-dimensional distribution of leaf orientation. The three-dimensional distribution needs to be routinely collected in diurnal sun angle studies and incorporated into mathematical models of sensor response.

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Thermal IR exitance model of a plant canopy

Cited by 43 publications

References 19 publications

A conceptual model for effective directional emissivity from nonisothermal surfaces

A conceptual model for effective directional emissivity from nonisothermal surfaces

Simulation of Directional Emission from Vegetative Canopy using Monte-Carlo Method

Diurnal variations of vegetation canopy structure

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