Variability of stratospheric ozone and aerosol in 1995 to 1997 derived from SAGE II and HALOE measurements

Stratospheric ozone observed by the Stratospheric Aerosol and Gas Experiment (SAGE) II and by the Halogen Occultation Experiment (HALOE) as well as stratospheric aerosol properties (surface area and volume densities) derived from the two experiments are analyzed. 370 SAGE II-HALOE coincident events are identified, using the coincidence criteria of flights falling within 2 degrees in latitude, 2 degrees in longitude, and 24 hours in time, during the 1995-1997 non-volcanic period.

Ozone and aerosol in the lower stratosphere often act as quasi-conservative tracers for dynamic processes; thus, ozone and aerosol profiles between SAGE II and HALOE within this small spatiotemporal window are expected to show good agreement. In general, the agreement seen in ozone profiles is much better than that for aerosol properties. This can be attributed to the following two reasons. First, ozone densities are conserved better than aerosol extinctions; thus, ozone profiles are expected to exhibit less variability. Second, SAGE II and HALOE measure aerosol extinctions at different wavelengths and use different retrieval methods to derive aerosol properties. Discrepancy seen in aerosol properties is in part produced through the retrieval processes.

Several cases showing poor agreement have been found, indicating local variations. High-resolution trajectory calculations are conducted for these cases to investigate the possibility of small-scale dynamic variations. How the occurrence of local variations vary with latitude, longitude, and season is also investigated.