Intercomparison of Stratospheric Aerosol and Gas Experiment (SAGE) with Umkehr[64] and Umkehr[92] ozone profiles and time series: 1979-1991

Analyzing coincident observations of ozone profiles at 15 Umkehr stations with Stratospheric Aerosol and Gas Experiment (SAGE) I and SAGE II measurements within 1000 km and 12 hours in low-aerosol conditions between 1979 and 1991, we find improved agreement between Umkehr and SAGE retrievals using the new (1992) Umkehr algorithm compared to the previous(1964) algorithm, but some significant differences remain. The column ozone amounts in layers 4 through 10 for both old Umkehr[64] (after adjustment for the scale change from the International Ozone Commission/World Meteorological Organization 1968 scale to the Bass and Parts [1985] scale) and new Umkehr[92] retrievals are approximately 5-6% lower than SAGE column amounts. The structure of the aerosol-corrected Umkehr[92] profiles compares much more favorably to SAGE than did the Umkehr[64] profiles in layers 4 to 7 (20-35 km), with considerable consistency in the vertical structure of differences across most sites. The layer-ozone differences, however, increase from zero in layer 4 to -15% (Umkehr[92] low) in layer 8. Belsk and Sapporo are the only 2 sites of the 15 analyzed here that exhibit somewhat dissimilar vertical structure in their differences versus SAGE. The Umkehr[92] a priori climatology contains less ozone in the lower layers (2-5) than does SAGE and somewhat more in the upper layers (7-9). However, these differences in a priori climatology do not significantly affect the broad altitude structure in the SAGE-Umkehr layer-mean ozone differences. On average, the Umkehr[92] profiles possess a correlation between 0.3 and 0.5 (higher at some stations) with the SAGE-measured ozone in individual layers 4 to 8. The time series of the Umkehr[92] and SAGE measurements typically exhibit similar trends except for discontinuous changes noted at Mauna Loa and Kagoshima.