Effect of humidity on the optical constants of an atmospheric aerosol

The results of calculations of the complex refractive index of an atmospheric aerosol are analyzed. The calculations were made taking into account the complex composition of the aerosol particles for different values of the humidity of the surrounding medium. The spectral characteristics of a proposed synthetic model of the aerosol are investigated.     

Dissipative instabilities in a mesospheric plasma with the aerosol charging processes taken into account

We consider dissipative instabilities of a flow of large aerosol particles as a possible mechanism for generation of electric-field and charged-particle density irregularities in the middle atmosphere. A dispersion equation describing the properties of the spectral component of a quasistatic electric field with allowance for the aerosol charging inertia and external stationary electric field is obtained. The equation is used to study characteristics of two possible instabilities, namely, the instability of a dust-acoustic mode and the instability of an additional low-frequency mode stimulated by the charging inertia. Dependences of the growth rates of both instabilities on the parameters of the medium and the external stationary electric field are obtained. Quantitative estimates for the parameters of the aerosol, ion, and electron components and external factors that are necessary for the excitation of instabilities in the region of the existence of summer polar mesospheric echo, as well as those for spatial scales of unstable perturbations, are given.     

Transmission of radiation through an aerosol medium

The properties of radiation through an aerosol medium have been achieved. This has been done by employing Mie scattering theory to calculate the radiation transfer scattering parameters in the form of extinction, absorption and scattering efficiencies. The equation of radiative transfer for the heat flux through a plane parallel atmosphere of aerosol has been solved. The aerosol size distributions are found in practical systems. Average efficiencies over size distribution for spherical particles of complex refractive index are calculated. Therefore, the radiative properties of stratospheric aerosols have been done. The obtained results found to be in a good agreement with the previous work.     

气溶胶凝聚粒子散射特性的数值计算

利用Cluster-cluster aggregation (CCA)模型,模拟了由相同数目球形原始微粒凝聚而成的四种随机取向气溶胶凝聚粒子．根据物质的电结构,将气溶胶凝聚粒子离散为一系列偶极子,结合离散偶极子近似方法,在获得每一个偶极子的电偶极矩之后,数值计算了气溶胶凝聚粒子散射强度的角分布,并分析了散射强度随入射光入射角度和气溶胶凝聚粒子尺寸参数变化的规律．结果显示：当散射角较小时,气溶胶凝聚粒子取向和入射光的入射角度对散射强度影响不大,当散射角增大时,散射强度则明显依赖于气溶胶凝聚粒子取向和入射光的入射角度;对于不同尺寸参数的气溶胶凝聚粒子,在同一角度入射情况下,随尺寸参数的增加,气溶胶凝聚粒子的散射主要集中于前向散射．     

随机取向气溶胶凝聚粒子光学特性研究

利用Cluster-cluster aggregation (CCA)模型,模拟了由64个球形原始微粒凝聚而成的四种随机取向气溶胶凝聚粒子。结合离散偶极子近似方法,分别得到了不同入射角和不同尺寸参数情况下气溶胶凝聚粒子的吸收、散射、消光效率因子和不对称因子的数值结果,并比较分析了四种形状气溶胶凝聚粒子吸收、散射、消光效率因子和不对称因子的差异。结果显示：对于相同数目原始微粒的气溶胶凝聚粒子,其光学特性明显依赖于入射光的入射角度和气溶胶凝聚粒子的形状;对于不同尺寸参数的气溶胶凝聚粒子,当入射光波长给定时,吸收、散射和消光效率因子最初随尺寸参数增大而快速增大,随后又随尺寸参数增大缓慢变小,但在尺寸参数变化过程中存在一个极大值;不对称因子则随尺寸参数的增大一直呈增大趋势,且随尺寸参数的增大趋近于1。     

On the relationship between the eulerian and lagrangian statistics of a brownian particle

Statistics of particles (smoke aerosol in the atmosphere) reaching a prescribed spatial region are analyzed. The effects of both regular and random forces acting on the particles are taken into account. A method is proposed for calculating the probability distributions of various quantities (time required to reach a prescribed location, particle velocity in its vicinity, etc.), and its scope is determined as depending on the parameters of the problem.     

Dynamic state of the atmosphere in aerosol components

An approach to analyzing experimental data on the size distribution and concentrations of atmospheric aerosol particles and meteorological parameters by using the flicker-noise spectroscopy is proposed. This approach makes it possible to identify the character of evolution of the measured parameters due to the processes underlying their variation, to trace the relationship between measured quantities, and, based on this, to determine the mechanisms of interactions between aerosol particles and gaseous components of the atmosphere. As an example, the behavior of the concentration, average particle size, and relative humidity of the atmosphere is examined. Atmospheric measurements were carried out at the recreation center in Tishkovo (Moscow Region). The proposed approach may prove useful in solving ecological and environmental problems.     

Self-focusing and multiple filamentation of laser light in disperse media

We present the results of a computer simulation of the initiation and formation of filaments under conditions of high-power laser pulse scattering on atmospheric aerosols. We demonstrate that the femtosecond filament is robust to the perturbations induced by a disperse medium and can transport a high-fluence energy for long distances. At sufficient pulse power, the intensity perturbations, caused by the interference of light scattered on particles, initiate the generation of filaments and result in multiple filamentation. The results were obtained using the stratified-medium approach of coherent light scattering on an ensemble of aerosol particles.     

Interaction of fine-dispersed aluminum particles in an argon medium with powerful laser radiation at different wavelengths

We have experimentally studied the dynamics of the extinction coefficients of laser radiation at wavelengths 10.6, 1.06, and 0.53 μm in a gas-dispersed medium based on aluminum aerosol in an argon atmosphere. Based on measurement results, we have derived calculation relationships for the concentration of aerosol particles and their size and analyzed the interaction efficiency of the radiation at these wavelengths with particles of the fine-dispersed medium.     

利用激光光梯度力消除气溶胶雾霾粒子的机理研究

针对气溶胶雾霾粒子在大气流中所受力的平衡体系(旋转升力平衡重力, 粒子与粒子之间依靠斥力形成稳定的网状的力平衡体系)的问题, 提出了用激光光梯度力破坏力平衡进而消除雾霾的新机理. 首先, 根据牛顿第二定理, 得到了粒子所受力的非线性方程组, 应用Runge-Kutta 法积分求解了雾霾颗粒在大气流中所受的主要力(空气曳引阻力、范德瓦耳斯斥力、旋转升力)的数值, 成功验证了西安市2013年12月17-25日、2014年2月20-26日两次雾霾检测试验结论: 在雾霾过程中, 粒径在0.5-0.835 μm径段的粒子数浓度增加最明显. 其次, 在雾霾粒子形成的均匀介质中, 计算了激光光梯度力的大小. 研究发现, 激光光梯度力的数量级恒大于雾霾颗粒所受主要力的数量级, 激光光梯度力完全可以破坏雾霾颗粒所受力的平衡体系. 因此, 用激光光梯度力消除雾霾是可行的, 这种新的解决雾霾的方法对人们的实际生活、环保及创建美丽的蓝天具有非常重要的意义.     

Modelling of two-phase,transient airflow and particles distribution in the indoor environment by Large Eddy Simulation

Prediction of particles distribution in the smaller-scale atmospheric environment, such as the indoor atmosphere, is of major importance for the comfort and the well-being of its occupants. The objective of this study is to investigate the airflow and particles transport, as well as the particles concentration evolution indoors, using Computational Fluid Dynamics (CFD) techniques. A three-dimensional, Euler–Euler two-phase flow model for the investigation of the indoor aerosol is developed, within a CFD general-purpose computer program (PHOENICS), and is validated against experimental measurements from the literature, for an ordinary case of indoor dilute aerosol. Turbulent flow is simulated by Large Eddy Simulation (LES) and the results are compared with those obtained applying the Reynolds-averaged Navier–Stokes (RANS) equations together with the ReNormalisation Group (RNG) k–? model. Τwo-way coupling between the two phases is modelled by means of appropriate interphase interactions. This study focused on particles of one size group (mean aerodynamic diameter of 10 μm) but the numerical method described can equally well be applied for a broader size range. It is concluded that for the very dilute aerosols considered here, simpler models (such as single-phase and drift flux) do as well in predicting the important parameters of the flow, as the more complex ones.     

The reflection and polarization properties of non-spherical aerosol particles

In this paper, we investigate the capability of multi-angle TOA reflectance and polarized reflectance for the retrieval of aerosol properties including aerosol mode (fine mode and coarse mode), aerosol shape (sphere and non-spherical), and aerosol optical thickness. Single-scattering parameters and phase-matrix elements were computed for randomly oriented non-spherical aerosol particles. Sensitivity indices were introduced to quantify the sensitivity of the TOA total reflectance and polarized reflectance to aerosol parameters. Finally, on the basis of the sensitivity study, this paper presents a conceptual approach toward the remote sensing of non-spherical aerosol three parameters (aerosol mode, aerosol shape, and aerosol optical thickness) using the TOA total reflectance and TOA polarized reflectance for the 0.865 μm spectral bands measured at multiple viewing angles.     

Photochemical sensitization and magnetic field effect on aerosol particle formation from a gaseous mixture of glyoxal and acrolein

Under light irradiation at 435.8 nm with a medium pressure mercury lamp, pure acrolein (AC) vapour does not produce any deposits, but a gaseous mixture of glyoxal (GLY) and AC produced sedimentary aerosol particles. The nucleation process of the aerosol particles was investigated by measuring He-Ne laser light intensity scattered by the aerosol particles as formed under light irradiation at 435.8 nm. From the dependence of the scattered light intensity on the partial pressure of GLY, it was found that electronically excited GLY in the nπ? state initiated chemical reactions with AC leading to nucleation of the aerosol particles. Magnetic field effects on the nucleation process were measured for a gaseous mixture of GLY and AC. With the application of a magnetic field of 5.3 kG, the nucleation reaction was accelerated, and the convection of the gaseous mixture was changed due to greater heat release during nucleation reaction between GLY and AC. The magnetic field effect on the gaseous mixture is discussed based on the photochemical behaviour of GLY.     

大气气溶胶粒子数密度谱和折射率虚部的测量

介绍一种综合利用光学粒子计数器和能见度仪测量大气气溶胶折射率虚部的新方法。首先，使用光学粒子计数器测量出大气气溶胶粒子的数密度谱(待订正)，用能见度仪同步测量出水平能见度。然后，根据球形粒子的米氏(Mie)散射理论，通过分析气溶胶粒子的折射率虚部、分档半径、粒子数密度谱、消光系数和能见度之间的关系，对分档半径进行订正，得到折射率虚部和能见度之间的对应关系。结合同步测量的能见度，反演出大气气溶胶粒子的折射率虚部。最后，利用折射率虚部对光学粒子计数器数据进行订正，得到大气气溶胶粒子的数密度谱。     

Transmittance of a gaseous medium with allowance for the molecular absorption and aerosol scattering

The transparency of a molecular gaseous medium comprising spherical aerosol particles is calculated. The characteristics of the transformed radiant energy that has passed through particles with different microphysical properties are analyzed. It is established that the joint effect of the molecular absorption and aerosol scattering in the IR range must be considered. Based on the characteristics of scattering particles, the boundary conditions are written that allow the molecular absorption and scattering to be considered separately. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 18–25, June, 2007.     

Elastic waves in suspensions

A model of heterogeneous medium taking into account the friction between the particles and liquid, as well as the relaxation of the small-size particles to the equilibrium on the stress, has been proposed to describe the propagation of the elastic waves in a suspension. A system of wave equations describing the propagation of a plane longitudinal wave has been formulated for the components of the medium. Analytical expressions for the sound velocity in a suspension has been obtained in the approximation in which the particles are completely carried away by liquid in the limiting cases in which the particles are in equilibrium under stress with the liquid or equilibrium is absent. The dependence of the sound velocity in the medium on the volumetric portion and the size of the inclusions has been studied. The obtained results agree with the experimental data and obtained analytical expressions for the sound velocity. The dynamics of the components of the medium at the propagation of the plane longitudinal monochromatic wave has been studied.     

气溶胶粒子散射和吸收特性对复折射率依赖性的数值研究

利用米散射理论数值计算分析了尺度参数为0.1~100时球形典型气溶胶粒子的散射和吸收特性对复折射率的依赖性关系。气溶胶粒子复折射率的实部和虚部是一个有机的整体,粒子复折射率的实部和虚部可以分别影响其散射和吸收特性。若实际大气气溶胶粒子大多是成核模态和积聚模态的小粒子,基于气溶胶的散射和吸收特性可以获得其复折射率的唯一解。但是,如果大气中存在大量的粗模态粒子时,气溶胶散射和吸收特性对其复折射率的依赖性较为复杂,只有选择有限的合适复折射率库区间,才有可能获得更合适的有效复折射率。     

整体毛细管X光透镜在大气颗粒物单颗粒分析中的应用

对大气颗粒物进行单颗粒X射线荧光(XRF)分析,是一种识别大气颗粒物来源的有力手段.为了利用实验室X射线光源对大气颗粒物进行单颗粒XRF分析,建立了基于整体毛细管X光透镜和实验室X射线光源的微束X射线谱仪.透镜焦斑处的功率密度增益在103数量级,焦斑直径为30 μm左右.该微束X射线谱仪对Fe-Kα线的最小探测极限为0.7 Pg.在Mo靶光源电压和电流分别为30 kV和50 mA的条件下,利用该谱仪对直径为9 μm的大气颗粒物单颗粒进行XRF分析时,测谱时间在180 s左右.实验表明,基于毛细管X光透镜和实验室X射线光源的微束X射线分析技术在大气颗粒物单颗粒分析中有着潜在的应用价值.     

Polarization of light and its use in various problems of optics of scattering media

As light passes through scattering media, certain specific features of the polarization of radiation manifest themselves. The paper presents materials on this problem that were obtained at the Institute of Physics of the National Academy of Sciences of Belarus over recent decades. Results of experimental investigations of media that model real objects are described for the case where the dimensionless optical parameters of media and objects coincide. A method for determining the position of a diffuse light source in the atmosphere via predominant oscillations of the light vector of scattered radiation for two directions of observation is proposed. The structure of aerosol formations (smokes, dust and liquid-droplet and crystalline clouds) is interpreted based on the character of depolarization of laser radiation sounding atmosphere. The polarization of laser radiation passing through a turbid medium and reflected from it is studied. Practical applications are proposed. Fundamentals of an applied vector theory of radiation transfer, which made it possible to considerably expand notions of light scattering in strongly turbid media, are given. Studies of light propagation in encapsulated liquid crystals, which are used for solving of a large number of problems, are described. In these objects, ordinary and extraordinary rays that arise in crystals under electric voltage can give rise to a wave that is attenuated to a different degree and whose phase and polarization characteristics are varying.