Morphological Characterization Of Particles And Aggregates And Scattering Properties Simulation

There are many suspended particles with different shapes in the real atmospherewhich can not influence the macro-kinetic characteristics of the atmosphere. However,they can affect the distribution and transmission of the solar energy through thescattering process. Meanwhile, the particle radius is almost at the same scale with theinfrared band, so the scattering of the particles has great influence on the transmissionof the infrared waves. More specifically, it can influence the heat which is emitted to thespace by the earth in the form of infrared radiation directly, which means it is verydifficult to emit to the space and results in greenhouse effect. In addition, because of theinfrared and polarization optical properties of the particles, they can weaken thedetection signal of the radars and shield from the visible light or even laser. There aremany applications in military and civilian, such as to defend from the laser weapons bymaking smog, to produce infrared stealthy materials using infrared particles. In a word,to study the scattering properties of the microparticles is of great significant in the fieldof industry, agriculture, medicine and military affairs.Based on this background, the paper presents the following three aspects ofresearch：(1) The parametric description of the single non-spherical particles in theatmosphere is presented. The impacts of the particle’s shape and hollow area on thescattering properties are considered. Also the influence of the bullet rosettes particles’branch number on the scattering properties is discussed. Research shows that the hollowarea can enhance the scattering properties of the single particle. In addition, the branchnumber can barely influence the scattering characteristic parameters in the scope ofsmall-scale parameters. However, beyond that range, the scattering characteristicparameters increase with the branch number when the absorption effect is considered,but there is no clear regularity when the absorption effect is ignored.(2) Based on the study of single particle, the research is extended to theaggregation particles. The scattering properties of the aggregation particles which aregenerated under the kinetics growth model CCA with different forms, structures andfractal dimensions are calculated. The impacts of the aggregate types, the scaleparameter and shapes of the aggregation particles on the scattering process of theaggregation particles are discussed. Research shows that the changing trends of thescattering intensity in parallel and normal direction of the aggregate particles with different types are uniform. However, when the interaction between the particles istaken into account, the scattering intensity in parallel direction of the particles despitethe aggregate type has a minimal value in the scattering angle of90°. In addition, for theaggregation of two particles, compared with the sphere particles, the Chebyshev shapehas no significant effect on the phase function, but the obtained values of the attenuationand absorption cross-section are relatively high. The ellipsoid has great influence on thescattering phase function in the scope of small-scale, but the obtained values of theattenuation and absorption cross-section are relatively low compared with the sphereparticles. The cylinder is similar with the ellipsoid, but the attenuation cross-sectiondecreases gradually as the scale parameter increases which changes from higher than thesphere to lower.(3) The multivariable fractal superposition algorithm is applied to fulfill themodeling of the3-D cloud scene. Based on the scattering calculation of the single andaggregation particle, the scattering process of a simulated cloud under the elevation of2.2km is calculated. The scattering properties of three kinds of clouds with differentparticles which are pure water cloud, water cloud with aerosol and low temperaturewater cloud with the combination of aerosol, cylinder ice particles, and aggregation iceparticles are compared. The result shows that the change trends of the attenuationcoefficient and the albedo of the three clouds are uniform. The maximum value of theattenuation coefficient corresponds to the cloud top and there is no significantrelationship between the clouds’ macro scattering properties.