Ozone Variability and Trends in the Upper Troposphere–Lower Stratosphere Using Multiple Tropopause Definitions and Observation Techniques

OCTAV-UTLS (Observed Composition Trends And Variability in the Upper Troposphere and Lower Stratosphere) is a recent SPARC activity contributing to improve the characterization of large spatial and temporal variability of atmospheric composition near the tropopause caused by competing transport, chemical, and mixing processes, as well as variations in the tropopause itself. Because of their varying representativeness and accuracy, a wide range of existing observations in the UTLS (aircraft, ground-based, balloon, and satellite platforms) must be used to fully characterize this variability.
In this framework, the long-term ozone variability and trends in the southwestern United States UTLS inferred from lidar at the JPL Table Mountain Facility and ozone soundings at the NOAA stations of Boulder, CO and Trinidad Head, CA were compared using multiple tropopause definitions and various dynamical coordinates. Results from the three stations are in very good agreement, revealing the strong impact of tropopause folds between 11 and 17 km, and pointing out the need to account for small spatio-temporal variability scales when using multiple observation techniques. Comparisons with aircraft (IAGOS) and satellite (Aura-MLS) measurements at the same locations provide a useful link towards a more hemispheric interpretation of the sources of ozone variability in this region