Interannual variability and long term changes in planetary wave activity in the middle atmosphere observed by lidar

Abstract. The upwelling planetary wave activity (PW) from the troposphere controls the intensity of the equator to pole transport of stratospheric ozone by the Brewer-Dobson circulation and thereby modulates the total ozone content at mid- and high-latitudes. Rayleigh lidar temperature data obtained from 1981 to 2001 at mid-latitude were used to study the interannual variability of PW activity in winter (October to April). The spectrum of stratospheric temperature fluctuations exhibits 2 peaks corresponding to 2 dominant modes of free travelling Rossby waves known as 16 day- and 12 day-waves. The 12 day-wave activity is shown to be anticorrelated with the equatorial QBO wind at 40 hPa. During the period 1981–2000 the global PW activity shows a negative trend for months October to January and a positive trend in March and April.