Seasonal variations in the semi-diurnal tide in the upper atmosphere as determined from radio meteor observations

Abstract

Corrections to the wind velocity for finite width of aerial polar diagram, and for non-uniform sensitivity of the radio meteor method to different values of velocity, have been calculated for eight stations in the northern hemisphere. The corrected wind data are used to study seasonal changes in phase and amplitude of the semi-diurnal tide in the upper atmosphere. These seasonal variations are analysed into harmonic components of periods 12, 6, 4 and 3 months; the component of period 12 months is found to have the largest amplitude. Similarities of seasonal behaviour are evident at all eight stations.