Radiative characteristics of plant leaf

Estimation of the efficiency of the hybrid LIDAR-DOAS system of lidar sensing of the polluted atmosphere using pulsed excilamps

“…It is obvious that the prospects for practical development of multi-purpose systems of remote monitoring of the gaseous atmospheric composition are in the constructive combination of the best characteristics of lidar sensing systems with the technique of differential optical spectroscopy. For this purpose, we now have favorable conditions following from the above-indicated progress in technique of manufacturing excilamps and wideband laser systems [7,24]. As already indicated above, the DOAS methods, both active and passive, though having all the above-enumerated advantages, do not ensure the possibility of monitoring of the well-known gaseous impurities with resolution in the spatial coordinate.…”

“…A significant disadvantage of the available DOAS monitoring systems is that in most cases, xenon high-pressure lamps that require high-power energy supply, cooling, and special safety measures for their operation are used for wideband radiation sources [4][5][6]. In this regards, fast development of wideband fiber optic lasers doped with ions of rare-earth elements seems to be promising [7]. Unfortunately, their energy parameters in the UV range of the spectrum, where the most informative absorption bands of the majority of greenhouse gases are localized, remain modest [8].…”

Statistical modelling of laser induced fluorescence in plant cover

“…Figure 2 illustrates the transformation in the spectral behavior of LIF as the geometrical thickness of a leaf increases over Δh = 0.1-1.0 mm (and, therefore, its optical thickness) for a constant value of w b = 0.3. The high optical density of the parenchyma of a leaf (β 01 (λ = 0.53 μm)=8750 m -1 [18]) means that essentially all the multiple scattering background remains within the detector viewing angle even when it is small, i.e., Θ d = 0.001 rad. The most important transformation in the spectrum occurs at wavelengths λ ≥ 0.71 μm, where the absorption band of chlorophyll ends.…”

“…As model parameters in the present case we draw on earlier [18] estimates of the spectral coefficients of scattering β sl (λ) and absorption β el (λ) (β sl (λ) + β el (λ) = β 1 (λ)) for the parenchyma of a dicotyledonous leaf. Without dwelling on the details of the justification for this, which has been discussed in detail elsewhere [18], we note that the choice of a dicotyledonous model for the leaf does not greatly reduce the generality of the results, since a model of this sort is most typical for arboreal, as well as grassy plants [17,19]. A leaf, in turn, is approximated as a plane parallel slab, whose thickness Δh 0 is also a parameter of the problem.…”

“…is the absorption coefficient of the leaf material owing to thermal dissipation; α F (λ) is the absorption by the fluorophors; β sl (λ) is the elastic scattering coefficient; n is the average refractive index of the leaf material; v is the speed of light in air; G Σ (r, Ω, Ω′, λ) = Σ i K i G i (r, Ω, Ω′, λ), where G i (r, Ω, Ω′, λ) is the directed elastic light scattering coefficient for the i-th phase component of the medium; and K i are weighting coefficients (for details, see [18]). The attenuation coefficient β s associated with geometric covering of the light beam by leaves is, by definition, independent of the wavelength of the incident radiation and is determined solely [25] by the surface density u 1 [m 2 /m 3 ] of leaves and the distribution function of the leaf normals Ω 1 ; β s = u 1 2π ∫ 0 2π g l (r, Ω 1 )⏐Ω′Ω 1 ⏐dΩ 1 ; and, Φ 0 (r, Ω, t, λ) is a function of the internal radiation sources occurring in the volume of the dispersed medium.…”