A method for calculating the motion characteristics of fractal-like aggregates based on the use of gas-kinetic results for homogeneous spherical particles is presented. The essence of the technique consists in replacing the real fractal aggregate by equivalent sphere with the mobility radius and in approximation of density and thermal conductivity of particles by their effective values. This method confirmed its efficiency in comparison with known experimental data.
New model describing the photophoretic motion of fractal-like soot aggregates is presented. The comparison with known experimental data has been performed and their good qualitative and quantitative agreement has been found. The calculated characteristics of the motion of fractal-like soot aggregates in the atmospheric radiation field are presented. The analysis of possible atmospheric manifestations of soot aggregate dynamics in the field of the atmospheric radiation predicts high transport possibilities of photophoresis at heights of the upper troposphere and middle stratosphere.
Results of the theoretical analysis of effective density and heat conductivity for compact and fractal-like particles are presented. It is shown that estimations on the basis of Evans et al model (2008) predict reliable values of heat conductivities for fractal-like aggregates. The complete set of thermal-physics parameters necessary for theoretical description of fractal-like particles motion (drag force, photophoresis, thermophoresis) is discussed.
The brief review concerning sources, altitude distribution and dynamics of soot aerosol in stratosphere is presented. Possible experimental approaches for registration of soot particles and predictive methods for research of their dynamics in stratosphere are discussed.
The software package for calculation of optical and microphysical parameters and motion characteristics of aerosol
particles in the stratosphere in the field of atmospheric radiation, temperature and wind was developed. Specialized
aerosol solver include various parts for calculating the optical and thermal characteristics of the particles: unit for
calculation of atmospheric radiation field (incident shortwave and outgoing thermal radiation); unit for the wind field
calculation for the standard atmospheric models; unit for calculation of particle motion characteristics for different
altitudes in stratosphere and mesosphere. The microphysical model of photophoretic motion of soot aggregates taking
into account them fractal structure is presented. Comparison with known experimental data is executed, and good
qualitative and quantitative agreement is revealed.
The results of the specialized aerosol solver development for calculation of optical and microphysical parameters and motion characteristics of aerosol particles in the stratosphere in the field of atmospheric radiation, temperature and wind are presented. This solver will include various parts for calculating the optical and thermal characteristics of the particles (for homogeneous spherical and fractal-like particle models); unit for calculation of atmospheric radiation field (incident shortwave and outgoing thermal radiation); unit for the wind field calculation for the standard atmospheric models; unit for calculation of particle motion characteristics for different altitudes in stratosphere and mesosphere. Application of the software package should significantly ease the time-consuming calculations of the stratospheric aerosol dynamics and allow to use it as a standard tool in future studies.
For the first time the results for photophoretic motion characteristics of fractal-like soot aggregates in the field of shortwave solar and long-wave thermal atmospheric radiation are presented. It is shown that for the model of fractal-like particles the photophoretic effects for soot aerosol in stationary atmosphere are most essential at stratospheric altitudes.
Results of theoretical estimations of effective heat conductivity for fractal-like soot aggregates on the basis of Evans et al. (2008) theory are presented. It is shown that these estimations give an adequate values of this parameter essentially important for calculations of characteristics of photophoretic motion of soot aggregates. Comparison of the developed theory for fractal-like particles photophoresis with experimental data of Karasev et al. (2004) demonstrates high efficiency of the offered approach.
Results of comparison for measured earlier velocities of photophoretic motion of fractal-like soot particles (Karasev et al., 2004) with the theory of photophoresis for spherical homogeneous particles (Beresnev et al., 1993) are presented. It is shown that presented comparison is quite possible, and gives the helpful and rich information for the further development of the rigorous quantitative theory of fractal-like particles photophoresis.
The annual behaviors of the aerosol optical depth (AOD) in some regions from Ural to Russian Far East are compared on the basis of monthly and decadal averages in two data samples: “all data” and “without fire smokes”. It is shown that when the smoke events are excluded, the average AOD values vary more smoothly during the year. Parameterization of the annual behavior of the spectral dependence of AOD is presented by the example of results obtained in Tomsk.
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