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 stratosphe re and lower mesosphere are observed in ISAMS CO data from April to July 19 92. CO-derived mean April-to-May upper stratosphere descent rates of 15 K/d ay (0.25 km/day) at 60 degrees S and 20 K/day (0.33 km/day) at 80 degrees S are compared with descent rates from diabatic trajectory analyses. At 60 d egrees S there is excellent agreement, while at 80 degrees S 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 wa ve 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 f rom 40 to 50 km and shows virtually Ilo phase tilt with height.