Lidar observations of the stratospheric aerosol during 1993 above McMurdo Station, Antarctica

Scattering ratios of stratospheric aerosol obtained by lidar at McMurdo Sta tion, Antarctica (78 degrees S, 167 degrees E), during February-December 19 93, have been analysed in relation to the stratospheric polar vortex. Seaso nal changes in their properties are used to infer dynamic processes occurri ng in the Antarctic stratosphere during the year. Descent rates are calcula ted and compared to values obtained with different studies. Our analysis su ggests that the apparent springtime cleansing of the Antarctic stratosphere is the result of subsidence of air masses inside the vortex and of sedimen tation of larger particles. Below 20 km of height, an enhancement of the ae rosol descent rates during July was associated with high occurrence of Pola r Stratospheric Cloud events above McMurdo Station in that period. A synopt ic approach using potential vorticity values at 425 K above the station has been employed to figure out the behaviour of the aerosol across the vortex boundary during its early formation. (C) 2000 Elsevier Science Ltd. All ri ghts reserved.