An analysis of northern middle‐latitude Umkehr measurements corrected for stratospheric aerosols for 1979–1986

Abstract

Umkehr observations of ozone profile for five northern middle‐latitude Dobson spectrophotometer stations are objectively corrected for stratospheric aerosol during the period 1979–1986. The corrections are done by means of theoretical calculations, using observations of stratospheric ozone and aerosols. Stratospheric ozone and aerosol profile data to correct the Umkehr measurements are derived from ozonesonde observations and observations provided by five lidar stations in the northern hemisphere middle latitudes. Optical properties of the stratospheric aerosol existing during and after the major injection by El Chichón are derived from surface and aircraft photometric observations and in situ aircraft observations of aerosol size distribution. The corrected Umkehr data display some noteworthy ozone reductions in the upper stratosphere. The magnitude of these reductions does not seem to be extraordinary when considering features seen in long‐term Umkehr data. However, the rates may be extraordinary, for example, in layers 8 and 9, in which decreases in ozone concentration during 1979–1986 were 9% and 15% respectively, using corrected data.