Multiyear global climatology of mesoscale variations of atmospheric parameters at altitudes 2 - 35 km from radio occultation experiments with low-orbit satellites receiving GNSS signals is considered. Numerical filtering of vertical radio refraction profiles gives information about standard deviations of variations with vertical scales less than 8 km. Global distributions of the standard deviations are subjects for significant inter-annual changes in the tropo-stratosphere. Seasonal changes of radio refraction and temperature standard deviations obtained with Microlab 1, CHAMP and COSMIC satellites are analyzed and compared. At low latitudes, quasi-biennial oscillations exist. The causes of mesoscale variability may be convection, acoustic-gravity waves and turbulence in the atmosphere.