Effects of tropical deep convection on upper tropospheric ozone concentrations

Ozone (O₃) is harmful to breathe at the surface and acts as a greenhouse gas in the upper troposphere. It has become important to understand how O₃ is distributed throughout the troposphere and how its distribution changes with time. This study focused on variations of O₃ in the tropical upper troposphere over the Atlantic Ocean. It is hypothesized that tropical deep convection reduces O₃ in the upper troposphere because the air processed through the storm updraft originates in a relatively pristine region at low altitudes. NSF/NCAR Gulfstream V (GV) Aircraft observations from the PRE-Depression Investigation of Cloud-systems in the Tropics (PREDICT) project along with cloud top temperatures calculated from infrared satellite images are used. To examine the relationship of O₃ fluctuations with other variables, deviations from the mean vertical profile of O₃ and potential temperature are calculated. Condensed water content greater than 0.0722 g m^-3 and cloud top temperatures colder than the plane's temperature plus 4˚C identify periods when the GV was in cloud produced by deep convection. We find a decrease in upper tropospheric O₃ concentrations 76% of the time that the GV was in cloud. O₃ concentrations outside of clouds vary as much or more than the variations measured while in convection. O₃ concentrations decrease 61% of the time potential temperature deviations are negative. Instances where in-cloud O₃ was not reduced may indicate O₃ sources from lightning or the transport of air from non-pristine boundary layers. This research contributes to a better understanding of the behavior of O₃ distribution.