The global structure and propagation of large-scale (periods > 5 days) waves at middle and high latitudes are examined using temperature data in the altitude range from 10 km to 90 km (from the upper troposphere to the upper mesosphere). The data are obtained from GPS radio occultation measurements by the COSMIC satellite constellation and the MLS-AURA satellite. Spectral analysis has revealed distinct 10-, 16- and 23-day planetary wave perturbations at high latitudes. The source of these perturbations is investigated employing UKMO temperature and wind assimilated fields. The inter-hemispheric coupling of these waves is also investigated and discussed.