Large-Scale Dispersion of Clusters of Particles in the Atmosphere

Abstract

The characteristics of the relative particle displacement tensor, the correlation functions, and spectra of the relative particle velocities at 200-, 500- and 850-mb levels are investigated. It is found that similarity and stability exist for the autocorrelation functions as well as the power spectra at various levels, which indicate that a quasi-stationary process exists in the large-scale relative diffusion in the atmosphere. The high frequency portion of the power spectra of both the zonal and meridional components of the relative velocities is found to be more or less proportional to k−8; the relative meridional velocity shows a maximum at the low frequency end. The low frequency portion of the cross spectra of the zonal and meridional relative velocities at 850 mb shows an opposite transfer to that at 200 mb. The mean square of the relative zonal displacement at a level is found to be about twice that of the relative meridional displacement at that level. It is also found that anisotropy exists in the field of the large-scale turbulent dispersion and that the major axis of the dispersion is generally oriented in the ESE to WNW direction.