The role of convection in tropical ozone trends (1998-2018) based on SHADOZ profiles
Thompson, A., Stauffer, R., Witte, J. C., Kollonige, D. E., Wargan, K., & Ziemke, J. R. (2021). The role of convection in tropical ozone trends (1998-2018) based on SHADOZ profiles. In 101st AMS Annual Meeting. American Meteorological Society (AMS).
Quantifying variability in lowermost stratosphere (LMS) ozone has become an important topic in the trends and climate assessment communities because of feedbacks among changing temperature, dynamics and species like water vapor and ozone. Most LMS evaluations are made with satellite observations.... Show moreQuantifying variability in lowermost stratosphere (LMS) ozone has become an important topic in the trends and climate assessment communities because of feedbacks among changing temperature, dynamics and species like water vapor and ozone. Most LMS evaluations are made with satellite observations. Likewise, assessments of tropospheric ozone profiles are carried out using commercial aircraft measurements. Ozonesondes constitute an independent reference dataset that encompasses both troposphere and LMS with 100-150m resolution. We used reprocessed Southern Hemisphere Additional Ozonesondes data from 1998-2018 to analyze variability and trends in free tropospheric (FT) and LMS ozone across five well-distributed tropical sites. A summary of our findings: (1) Only one of our five sites, the equatorial Americas region, exhibits small positive FT and negative LMS ozone trends on an annually averaged basis. (2) At the other 4 sites, trends only occur in isolated layers during months with decreasing (February-April) or increasing (July-September) convection. (3) The latter are always positive ozone changes in the FT. Our results do not support a picture of large, near-uniform tropical FT O3 increases as reported in published studies with satellite and commercial aircraft ozone profiles. They do imply that in the urban tropics where rising emissions create additional ozone, the trends observed in aircraft profiles may overlie smaller FT ozone increases caused by perturbed dynamics. We also provide regional and seasonal trends that can be compared to LMS ozone changes that are typically reported as zonal averages. In the 2nd half of the year, when LMS ozone is a maximum in the seasonal cycle, there are small decreases in ozone. These may be related to an increase in tropopause height. Show less