Antarctic polar descent and planetary wave activity observed in ISAMS CO from April to July 1992

Antarctic polar descent and planetary wave activity in the upper stratosphere and lower mesosphere are observed in ISAMS CO data from April to July 1992. COderived mean April-to-May upper stratosphere descent rates of 15 K/day (0.25 km/day) at 60S and 20 K/day (0.33 km/day) at 80S are compared with descent rates from diabatic trajectory analyses. At 60S there is excellent agreement, while at 80S the trajectory-derived descent is significantly larger in early April. Zonal wavenumber 1 enhancement of CO is observed on 9 and 28 May, coincident with enhanced wave 1 in UKMO geopotential height. The 9 May event extends from 40 to 70 km and shows westward phase tilt with height, while the 28 May event extends from 40 to 50 km and shows virtually no phase tilt with height.