The radiation regime and architecture of plant stands

Ross, Juhan

doi:10.1007/978-94-009-8647-3

Cited by 1,169 publications

(775 citation statements)

References 89 publications

(134 reference statements)

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“…A series of different mathematical kernels can be selected to optimize BRDF models for various kinds of vegetation cover. Among the most commonly applied functions are Ross and Li Kernels 13 (Wanner et al, 1995, Lucht et al, 2000, Strugnell and Lucht, 2001) with the Ross kernels (Roujean et al 1992) based on the radiative transfer theory of Ross (1981), whereas the Li kernels are geometric-optically based (Li and Strahler, 1986). Both types of kernels are examples of physical reflectance models.…”

Section: Brdf Notationmentioning

confidence: 99%

Separating physiologically and directionally induced changes in PRI using BRDF models

Hilker¹,

Coops²,

Hall³

et al. 2008

Remote Sensing of Environment

170

150

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Section: Brdf Notationmentioning

confidence: 99%

Separating physiologically and directionally induced changes in PRI using BRDF models

Hilker¹,

Coops²,

Hall³

et al. 2008

Remote Sensing of Environment

170

150

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“…Since green leaves usually absorb 85%-90% of intercepted radiation in the photosynthetically active region of the solar spectrum, F BS can be approximated by the fraction of direct incident PAR that the vegetation canopy transmits. This fraction follows Beer's law, given by exp[− G(θ 0 ) · LAI / cos(θ 0 )], where θ 0 is the solar zenith angle, and G(θ 0 ) is a geometric factor defined as the projection of unit leaf area onto a plane perpendicular to the illumination direction (Ross, 1981). Thus,…”

Section: Obtaining New Information On Canopy Structure From Misr Prodmentioning

confidence: 99%

Analysis of the MISR LAI/FPAR product for spatial and temporal coverage, accuracy and consistency

Tan

et al. 2007

Remote Sensing of Environment

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The Multi-angle Imaging SpectroRadiometer (MISR) instrument provides global imagery at nine discrete viewing angles and four visible/nearinfrared spectral bands. MISR standard products include green leaf area index (LAI) of vegetation and fraction of photosynthetically active radiation absorbed by vegetation (FPAR). This paper describes the research basis for transitioning the MISR LAI/FPAR products from provisional to validation status. The efforts included not only comparisons to field data but also analyses of relationships, consistency and complementarity between various MISR products derived by independent algorithms. For example, we show how the energy absorbed by the ground below vegetation can be estimated from two independent MISR products, FPAR and BHRPAR (bi-hemispheric reflectance at PAR wavelengths). Further, we show that this information can be used to derive at least three measures of canopy structure -Beer's law extinction coefficient, mean leaf inclination and the gap fraction or vegetation ground cover. The spatial and temporal coverage of the LAI/FPAR product is mainly limited by cloud contamination. However, when a successful aerosol retrieval is performed, typically 95% of pixels have surface reflectance retrievals suitable as input to the LAI/FPAR algorithm. The algorithm provides LAI/FPAR retrievals in 50-80% of these pixels with suitable input. The early versions of the algorithm overestimated LAI values in grasses and broadleaf crops. The MISR LAI product from the recalibrated algorithm (version 3.3) is assessed by comparison with field data collected in a 3 × 3 km agricultural area (grasses and cereal crops) near Avignon, France. LAI retrievals in other biomes are compared to MODIS LAI product of known accuracy. The MISR LAI product shows structural and phenological variability in agreement with data. Our results suggest that the product is accurate to within 0.66 LAI in herbaceous vegetation and savannas and is an overestimate by about 1 LAI in broadleaf forests. LAI retrievals over needle leaf forests remain at provisional quality level.

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“…is the area scattering phase function for species 'j' (Ross, 1981). The above parameters depend on the probability density of leaf normal orientation,…”

Section: The Approachmentioning

confidence: 99%

“…, ( L Ω r is a leaf normal direction) and the spectral leaf albedo, ) , r ( λ ω r ( λ is a wavelength) (Ross, 1981). Given the set of structural and optical parameters, the radiation regime in a vegetation canopy is described by the following 3D transport equation for radiation intensity, ) , r ( I Ω r r :…”

Section: The Approachmentioning

confidence: 99%

Stochastic radiative transfer model for mixture of discontinuous vegetation canopies

Shabanov

Huang

Knjazikhin

et al. 2007

Journal of Quantitative Spectroscopy and Radiative Transfer

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ABSTRACT:Modeling of the radiation regime of a mixture of vegetation species is a fundamental problem of the Earth's land remote sensing and climate applications. The major existing approaches, including the linear mixture model and the turbid medium mixture Radiative Transfer model, provide only an approximate solution to this problem. In this study we developed the Stochastic Mixture Radiative Transfer (SMRT) model, a mathematically exact tool to evaluate radiation regime in a natural canopy with spatially varying optical properties (mixture of vegetation species and gaps). The model solves for the radiation quantities, direct input to the remote sensing/climate applications: mean radiation fluxes over whole mixture and over individual species. The canopy structure is parameterized in the SMRT model in terms of two stochastic moments: the probability of finding species and the conditional paircorrelation of species. We performed analytical and numerical analysis of the radiation effects, simulated with the SMRT model for the three cases of canopy structure: a) non-ordered mixture of species and gaps (turbid medium); b) ordered mixture of species without gaps; c) ordered mixture of species with gaps. The analysis indicates that the variation of radiation fluxes between different species is proportional to the variation of species optical properties. Gaps introduce significant disturbance to the radiation regime in the canopy as their optical properties constitute major contrast to those of any vegetation species. The SMRT model resolves deficiencies of the major existing mixture models: ignorance of species radiation coupling via multiple scattering of photons (the linear mixture model) or overestimation of this coupling due to neglecting spatial clumping of species (the turbid medium approach). Overall, this study establishes an advanced theoretical basis for future mixture applications.

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The radiation regime and architecture of plant stands

Cited by 1,169 publications

References 89 publications

Separating physiologically and directionally induced changes in PRI using BRDF models

Separating physiologically and directionally induced changes in PRI using BRDF models

Analysis of the MISR LAI/FPAR product for spatial and temporal coverage, accuracy and consistency

Stochastic radiative transfer model for mixture of discontinuous vegetation canopies

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