Evidence of planetary-scale waves in the lower thermospheric winds

Abstract

Significant oscillations in the zonal wind at meteor heights with periods between 2 and 10 days have been found at Budrio (450N, 120 E) during four campaigns carried out in 1976, 1978, 1979 and 1980. These oscillations have now been established as the effect of zonally travelling planetary-scale waves. Long-period oscillations of nearly 2 and 5 days essentially occur in summer and winter, whereas, for equinoctial campaigns, waves of longer period are observed. Quasi-2-day oscillations represent probably an atmospheric free mode which exhibits considerable amplification after the summer solstice. Preliminary comparisons on this summer anomalous aspect have been made with the results obtained at Sheffield (U. K.) in the course of two cooperative campaigns performed in 1979 and 1980.