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- Author or Editor: A. S. Koziol x
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Abstract
The significance of the influence of turbulence on collisions and coalescence of small cloud droplets is still an outstanding problem. In particular, the growth of droplets in the radius range 10 to 15 µm is not well understood. The present research examines whether or not turbulence affects the growth rate of such small drops by simulating trajectories of two hydrodynamically interacting droplets in a turbulent field. The trajectories were calculated with a model based on linear Stokes hydrodynamics. Turbulence was modeled in the form of random Fourier modes with both the space and time spectra prescribed. Both spectra were characterized by Kolmogorov scaling. The space spectrum was modeled in the inertial and dissipation subranges. On the basis of scale analysis, only small-scale time variations were allowed, and the so-called Eulerian–Lagrangian time spectrum was applied. The results show that most collision rates increase moderately in a turbulent flow characterized by rates of energy dissipation of the order of 1, 10, and 100 cm2 s−3.
Abstract
The significance of the influence of turbulence on collisions and coalescence of small cloud droplets is still an outstanding problem. In particular, the growth of droplets in the radius range 10 to 15 µm is not well understood. The present research examines whether or not turbulence affects the growth rate of such small drops by simulating trajectories of two hydrodynamically interacting droplets in a turbulent field. The trajectories were calculated with a model based on linear Stokes hydrodynamics. Turbulence was modeled in the form of random Fourier modes with both the space and time spectra prescribed. Both spectra were characterized by Kolmogorov scaling. The space spectrum was modeled in the inertial and dissipation subranges. On the basis of scale analysis, only small-scale time variations were allowed, and the so-called Eulerian–Lagrangian time spectrum was applied. The results show that most collision rates increase moderately in a turbulent flow characterized by rates of energy dissipation of the order of 1, 10, and 100 cm2 s−3.
Abstract
In certain applications the, so-called, bin or sectional models are not adequate to model aerosol or cloud droplets. Therefore, the authors developed a continuous, high-resolution in size model of aerosol. The application of this model to the stratospheric Junge layer is presented. The equations with which to model the aerosol as well as the physics underlying the equations are described in detail. In the authors’ approach, the role of vertical advection is emphasized, and in particular, a realistic diffusion coefficient that eliminates vigorous, artificial mixing between vertical levels is used. The equations are solved using appropriate and accurate numerical methods. As a test, the one-dimensional version of the model is applied to the stratospheric aerosol for both quiescent and volcanic periods. The results are able to capture some characteristics of the Junge layer, which cannot be modeled with bin models with large diffusion. It is also found that the effect of a volcanic eruption on the aerosol population can be long lasting, up to five or six years.
Abstract
In certain applications the, so-called, bin or sectional models are not adequate to model aerosol or cloud droplets. Therefore, the authors developed a continuous, high-resolution in size model of aerosol. The application of this model to the stratospheric Junge layer is presented. The equations with which to model the aerosol as well as the physics underlying the equations are described in detail. In the authors’ approach, the role of vertical advection is emphasized, and in particular, a realistic diffusion coefficient that eliminates vigorous, artificial mixing between vertical levels is used. The equations are solved using appropriate and accurate numerical methods. As a test, the one-dimensional version of the model is applied to the stratospheric aerosol for both quiescent and volcanic periods. The results are able to capture some characteristics of the Junge layer, which cannot be modeled with bin models with large diffusion. It is also found that the effect of a volcanic eruption on the aerosol population can be long lasting, up to five or six years.
