Aerosol Effect on Umkehr Ozone Profiles using SAGE II Measurements

This study examines 1211 cases of coincident ozone profiles derived from 1164 Umkehrs and 928 SAGE II profiles within 1000 km and 12 hours between October 1984 and April 1989 to study the stratospheric-aerosol effect on Umkehr ozone profiles. Because of the close correspondence of stratospheric aerosol optical depth at the SAGE II-measured 0.525 micron wavelength and the extrapolated 0.32 Umkehr wavelength determined in this study, we use the 0.525 micron data to determine the aerosol effect on Umkehr profiles. At the 95% confidence level, we find the following errors to the Umkehr ozone amounts: in Umkehr layer nine (-2.9 ± 2.1), eight (-2.3 ± 1.1), seven (0.1 ± 1.1), six (2.2 ± 1.0), five (-1.5 ± 0.8), and four (-2.4 ± 1.7) in percent ozone amount per 0.01 stratospheric aerosol optical depth. These results agree with previous theoretical and empirical studies within their respective error bounds in layers nine, eight, and seven. The results in layers six, five, and four differ significantly from those in previous works. Using only those eight stations with more than 47 coincidences results in mean aerosol effects that are not significantly different from the 14-station results. Because SAGE II and Umkehr produce different ozone retrievals in layer nine and because the intra-layer correlation of SAGE II ozone and aerosol in layer nine is non-zero, one must exercise some caution in attributing the entire SAGE IIUmkehr difference in this layer to an aerosol effect.