GLOBAL DISTRIBUTIONS OF THE REFRACTION INDEX VARIANCES AT DIFFERENT ALTITUDES IN THE ATMOSPHERE FROM GPS/MET SATELLITE OCCULTATION DATA

Abstract

The GPS/MET satellite measurements during years 1995–1997 at altitudes 2–35 km are used to obtain global distributions of meso-scale variances of the refraction index (“dry temperature”) at different stratospheric altitudes. Individual dry temperature profiles are smoothed using second order polynomial approximations in 7 km thick layers centered at 2, 5, 10, 15, 20, 25, 30 and 35 km. Refraction index deviations from smoothed values and their variances are obtained for each profile and are averaged for each month of the year during the GPS/MET experiment. Global distributions of dry temperature variances have inhomogeneous structure. Locations and latitude distributions of the variance maxima and minima depend on altitudes and months of year. The reasons for the small- and meso-scale refraction index perturbations in the tropo–stratosphere could be meso-scale irregularities, turbulence and internal gravity waves. Magnitudes of the refraction index variances are larger in the regions of tropo–stratrospheric jet streams and of equatorial deep convection.