Condition of Retrieving Vertical Column Density of Atmospheric Pollution Gases by Using Scattered Solar Radiation

We present a method to monitor the vertical column density （VCD） of atmospheric pollution gases by using the scattered solar radiation. The necessary condition of capturing the useful scattered solar radiation is achieved. The condition is only dependent on the solar elevation angle, while independent of the solar azimuth angle, which could greatly simply the capturing equipment and procedure. Under the condition, the VCD of tropospheric NO2 in Chengdu, China is retrieved from the scattered solar radiation, which is close to that from the direct solar radiation.     

用太阳光谱测量空气中NO2浓度的方法研究

根据Noxon方法,利用NO₂在430—450nm范围内的吸收特性,测量空气中NO ₂的浓度.介绍了一种利用光学差分吸收原理,以太阳光为光源,二极管阵列为探测器 ,黄山光明顶上的太阳光谱为参考光谱测量大气中NO₂浓度的新光学方法. 关键词： 太阳光谱 2垂直柱体密度')" href="#">NO₂垂直柱体密度 定日镜 环境空气质量监测     

Attenuation of solar radiation by a water mist from the ultraviolet to the infrared range

A model is developed for the hemispherical transmittance of direct and scattered solar radiation from a cloudless atmosphere by a mist layer of water droplets in order to investigate the potential of water misting systems to serve as a protection from solar irradiation with particular emphasis on harmful UV radiation. The proposed model is based on published spectral experimental data for solar irradiation, Mie theory for interaction of the radiation with single spherical droplets, and radiative transfer theory. Known limiting solutions are employed to simplify the Mie calculations. The modified two-flux approximation is used to account for both direct and diffuse irradiation in lieu of a numerical solution for the full radiative transfer equation in anisotropically scattering media. The role of the governing parameters of a disperse water curtain of water droplets, water content, and droplet size for sample conditions is studied in some detail, particularly in the near-ultraviolet part of the spectrum where radiation can result in human tissue damage.     

Scattering of Solar and Atmospheric Background Radiation from a Target

Light scattering property of environment is very important in theoretical study and application of the remote sensing. What's more, it is valuable for infrared radiation, imaging, and the detection of target and tracking. In this paper, solar and atmospheric background radiation, and their scattering property from target are discussed. BRDF (Biodirectional Reflectance Distribution Function) is a very important quantity that shows the radiation and reflection feature of target. According to electromagnetic radiant and scattering theories, the relationship between laser radar scattering cross section (LRCS) and BRDF is introduced. LOWTRAN model is an effective method of calculating the spectral distribution of solar and atmospheric radiation. Here it is applied to compute solar and atmospheric background radiation scattered from a target. The relative equations are deduced. Thus, the spatial and spectral distribution of scattering light is given. As a special example, for the Lambert's surface, the equations are simplified. As a result, the spatial and spectral distributions scattering radiation of solar and atmospheric background from a rough painted surface are present. The scattering of solar radiation plays a primary role in MIR region, but scattering of atmospheric background radiation is higher in LIR region. At the same time, there is obviously specular reflectance for solar radiation due to coherent scattering from rough surface.     

Statistical estimates of the contribution of multiply scattered radiation to the intensity of acoustic radiation transmitted through a lower 500-m atmospheric layer

The problem of acoustic radiation propagation through a lower 500-m plane-stratified turbulent atmospheric layer has been solved by the Monte Carlo method. Statistical estimates of the contribution of multiply scattered radiation to the transmitted acoustic radiation intensity are obtained. A point omnidirectional source of monochromatic acoustic radiation was placed at a height of 35 m above the absorbing Earths surface. Statistical estimates of the contribution of multiply scattered radiation to the transmitted radiation intensity have shown that it does not exceed 15% for the outer scale of atmospheric turbulence L₀ = 10 m and sound frequency F = 1700 Hz, reaches 30% for L₀ = 20 m, and increases to 90% for L₀ = 80 m. A comparison of the calculated results with the available experimental data demonstrates their satisfactory agreement.__________Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 72–79, December, 2004.     

Cyclic Variations in the Solar Radiation Fluxes at the Beginning of the 21st Century

The solar activity in the current, that is, the 24th, sunspot cycle is analyzed. Cyclic variations in the sunspot number (SSN) and radiation fluxes in various spectral ranges have been estimated in comparison with the general level of the solar radiation, which is traditionally determined by the radio emission flux F_10.7 at a wavelength of 10.7 cm (2.8 GHz). The comparative analysis of the variations in the solar constant and solar indices in the UV range, which are important for modeling the state of the Earth’s atmosphere, in the weak 24th cycle and strong 22nd and 23rd cycles has shown relative differences in the amplitudes of variations from the minimum to the maximum of the cycle. The influence of the hysteresis effect between the activity indices and F_10.7 in the 24th cycle, which is taken into account here, makes it possible to refine the forecast of the UV indices and solar constant depending on the quadratic regression coefficients that associate the solar indices with F_10.7 depending on the phase of the cycle.     

A scheme for CO2 laser scattering to measure the ion temperature in a Tokamak plasma

A simple optical scheme is proposed for scattering of pulsed high-power CO₂ laser radiation from a plasma, and to achieve heterodyne detection to receive the very low scattered radiation intensity and resolve the narrow spectrum. Ion temperature measurement with microsecond time resolution in fusion oriented Tokamak plasmas seems feasible.     

UV spectral measurements at moderately high resolution and of OH resonance scattering resolved by polarization during the MANTRA 2002-2004 stratospheric balloon flights

A moderately high-resolution (<0.1 nm) grating spectrometer designed to measure the solar radiation in the spectral range 295-315 nm was flown on the MANTRA stratospheric balloon payloads of 2002 and 2004. The instrument measures both the direct sunlight and the radiation scattered by the atmosphere. The latter can be observed in two orthogonal polarization directions, at 90° from the solar azimuth and at several elevations above the horizon. As the OH molecule is the principal resonant scatterer in this spectral region, this permits the inference of both ozone and OH column amounts as well as limited profile information. This paper describes the instrument and its in-flight characterization, the basic data processing and the influence of several aspects of the flight profile. The direct sun measurements are analyzed both to characterize the spectrometer responsivity to scattered radiation and to estimate the ozone abundance at the flight altitude and above. An example of a high-resolution solar spectrum at 37 km altitude is presented and compared with others in the literature. The measured OH and Rayleigh-scattered spectra are used to derive OH radiation intensity measurements (the OH airglow), which are compared with others in the literature.     

直射太阳光差分吸收光谱法测量合肥NO2 整层柱浓度

直射太阳光差分吸收光谱技术(DS-DOAS)近 年来成功应用于大气痕量气体的垂直柱浓度测量. 本文研究了基于被动DOAS算法可用于连续测量NO₂整层垂直柱浓度的DS-DOAS技术, 介绍了测量系统的构成.利用统计最小值外推法减少了由参考谱引入的误差.分析了测量结果的误差来源, 估算了误差大小.报道了该系统在合肥地区对NO₂进行的连续11天的测量, 分析了测量结 果.通过实验验证了算法的可行性, 证实了该技术可实现连续测量NO₂整层垂直柱浓度.     

直射太阳光差分吸收光谱反演NO2整层垂直柱浓度

在直射太阳光差分吸收光谱技术(DS-DOAS)中,通常采用测量期间较干净大气条件下太阳天顶角最小时的测量谱作为参考谱反演整层垂直柱浓度(VCD)。由于参考谱中依然含有未知的NO2吸收结构,因此得到的是VCD的相对值。该文将大气外层高精度太阳夫琅禾费标准光谱与仪器函数卷积后作为参考谱,避免了参考谱中含有NO2的吸收结构引入的误差。通过研究3月7日用此新方法获得的斜柱浓度(SCD)与通常方法获得的差分斜柱浓度(dSCD)的比较,新方法反演SCD的误差小于1.6×1016 molecules.cm-2;通常方法反演SCD的误差在4.25×1016 molecules.cm-2附近,采用新方法误差减少了62%以上。最后将DS-DOAS测量的NO2整层VCD与多轴差分吸收光谱技术(MAX-DOAS)测得的NO2对流层VCD进行了对比,结果表明新方法可以有效的改进通常方法计算VCD的误差。     

Scattering of CO2 laser beam by a plasma of air breakdown at pressures of 1–300 torr

Results from experiments with a TEA CO₂ laser with an unstable cavity and a power of 10⁷ W are presented. Laser radiation was focused by a lens with a focal length of 100 or 150 mm in air free of dust (grains larger than 0.1 μm were filtered out). The power and energy of radiation scattered within a central cone of an annular laser beam was recorded. The dependences of the threshold (for scattering) laser power and the scattered power on pressure were determined. The angular divergence of the collimated scattered beam was found to be 3.9 mrad, which was close to the divergence of the laser beam (2.5 mrad). The amplification of the scattered radiation pulse was performed.     

Heterodyne detection of CO2 laser radiation scattered from a plasma arc jet

Observations have been made of CO₂ laser radiation scattered incoherently from an argon arc jet plasma. The heterodyne detection technique employed is discussed.     

Method for Describing the Angular Distribution of Optical Radiation Scattered by a Monolayer of Ordered Spherical Particles (Normal Illumination)

We have developed a method for describing the angular distribution of intensity of radiation scattered by a monolayer of homogeneous spatially ordered monodisperse spherical particles normally illuminated by a plane circularly polarized electromagnetic wave. The method is based on the quasicrystalline approximation (QCA) of the theory of multiple scattering of waves (TMSW) using the multipole expansion of fields and the tensor Green function in vectorial spherical wavefunctions. The method is applied for analyzing the characteristics of radiation scattered by a partially ordered monolayer and a monolayer with a nonideal lattice. The results of calculations are compared with the available experimental data on the position of the first-order diffraction peak on the angular and spectral dependences of the intensity of radiation scattered by a closely packed monolayer with a nonideal triangular lattice of SiO₂ particles. Good conformity of the results has been established.     

Numerical study of the extinction matrix for a plate crystal

Energy and polarization characteristics of optical radiation passed through a semitransparent plate crystal with a preset orientation in space are studied numerically within the framework of the method of physical optics. Results of calculations of the extinction matrix elements versus particle size, refractive index, crystal orientation, and incident radiation wavelength (from 0.5 to 15 μm) are presented. It is demonstrated that K₁₁, K₁₂, and K₃₄ are most informative among the elements of the extinction matrix. It is established that the first of them is most sensitive to changes in the microphysical and orientational parameters of the particle when the angle of radiation incidence on the plate changes from 0 to 20°, and the nondiagonal elements are most sensitive when the angle of radiation incidence is greater than 40°. The characteristics of the total field scattered near the forward direction are determined. It is established that their dependence on the physical parameters of the crystal is most strong at scattering angles smaller than or equal to 4° and wavelengths from the IR range (in particular, from the atmospheric transparency window).     

Flavor structure of the electroweak spectra of monoenergetic solar neutrinos scattered by electron

Electroweak and electromagnetic contributions to the spectrum of beryllium solar neutrinos scattered by an electron are investigated. The flavor structure of the electroweak spectrum with the content of electron neutrinos and admixture components ν _μ and ν _τ is analyzed.     

Light-induced scattering in photorefractive crystals

Light-induced scattering features in LiNbO₃- and BaTiO₃-crytals are compared with theories on holographic writing in photorefractive crystals. It is shown that they describe the experimental facts concerning the expected main scattering directions for a given incident polarization, the time development, the thickness and the wavelength dependence. Time records of the transmission offer a useful alternative for the determination of the photoconductivity. Furthermore, a new method for birefringence measurements is established. The high accuracy of this method is based on the automatic fulfillment of a phase matching condition by the anisotropically scattered radiation.     

Scattering of partially polarized light by aligned atoms

A compact expression for the cross section of scattering of an arbitrarily polarized light by aligned atomic systems is obtained, in which the dependence on the geometric parameters and the Stokes parameters specifying the state of partial polarization of the incident radiation is represented in explicit form. The effect of atomic alignment and the processes of dissipation of the light energy on the polarization specific features and the angular distribution of the scattered light is investigated. In particular, it is shown that, if a dissipative channel is accessible, the angular distribution and the degree of linear polarization of scattered light depend on the degree of circular polarization of the incident radiation η₂. Dissipative processes also induce the circular polarization of the light scattered by aligned atoms when η₂=0.     

基于高次余弦散射分布的空间卫星可见光特性

基于几何光学和辐射理论,研究了空间卫星的可见光散射特性.空间卫星的背景辐射主要包括太阳的直接辐射和地球及大气的散射辐射,根据目标的结构特性与背景特性建立了空间卫星的几何模型和光照模型.分析目标表面状况,入射到目标表面的光线近似服从高次余弦散射分布,根据能量守恒定理及表面材料的高次余弦散射分布特性建立了目标散射特性的数学模型.通过矢量坐标变换确定太阳、地球、观测卫星在目标本体坐标系下的相对位置关系.根据给定的几何尺寸和表面物性参量仿真获得了目标在探测器入瞳处的能量分布及星等特征,目标本体与太阳帆板在探测器入瞳处的辐照度最大量级均为10-12 W/m2.仿真结果表明太阳帆板在目标特性分析时不可忽略,为空间目标的可见光探测提供参考数据.     

Influence of laser heating on the optical properties of a superhigh-modulus organoplastic material

The degree and azimuth of polarization and the indicatrix of the intensity of radiation (λ=0.63 μm) reflected by the surface of a monodirectional superhigh-modulus organoplastic material after structural transformations induced in it by CO₂-laser radiation are measured. It is shown that the space-polarization characteristics of the radiation reflected by the organoplastic material charred as a result of laser heating correspond to the parameters of radiation scattered by a nontransparent material with an isotropic surface in the approximation of geometrical optics. B. I. Stepanov Institute of Physics, National Academy of Sciences of Belarus, 68, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 5, pp. 635–639, September–October, 1999.