The decay of the El Chichon stratospheric perturbation, observed by lidar at northern midlatitudes

The stratospheric perturbation caused by the April 1982 eruption of the Mexican volcano El Chichon (17.3 degrees N) passed through a maximum at northern midlatitudes ten months after the event. The following decay of the aerosol layer could be investigated until the end of 1985 when this period was terminated by renewed volcanism. Lidar backscatter measurements exhibit seasonal decay variations which can primarily be attributed to stratospheric column height variations. In addition, advection of particle loaded air masses contribute to this effect. With respect to the 1977/79 background situation the stratospheric aerosol layer decayed with an e-folding lifetime of about 1 year, when only summer observations were considered. (IFU)