In this paper we present analysis of the mean intensity, relative variance, and scales of temporal and spatial correlations of the intensity fluctuations of focused and collimated beams in the far zone of diffraction, when propagating through the turbulent atmosphere along slant and vertical paths whose lengths essentially exceed the thickness of a distorting layer.
It is shown that for such paths the time scale of correlation of the intensity fluctuations is identically characterized by the time required for the atmospheric inhomogeneities to travel across the initial laser beam cross section, irregardless of the level of turbulent distortions in the layer. The spatial scale of correlations coincides with diffraction size of the beam in the observation plane, if the amplitude fluctuations of the optical radiation within the layer are small compared with the phase ones, otherwise it is proportional to the radius of correlation of the field at the exit from the distorting layer.
It is also shown in this paper that maximum value of the mean intensity, if determined in the coordinate system with the origin at the energy center of gravity of a beam, can essentially exceed the mean intensity due to random wanderings.