Is There Evidence that Mid-Latitude Stratospheric Ozone Depletion Occurs in Conjunction with North American Monsoon Convection?

A recent study suggests that during the period of the summertime North American Monsoon (NAM), ozone depletion could occur as a result of catalytic ozone destruction associated with the cold and wet conditions caused by overshooting convection. Aura Microwave Limb Sounder (MLS) water vapor measurements do show that the NAM region is wetter than other parts of the globe in regards to both the mean and extremes. However, definitive evidence of ozone depletion occurring in that region has not been presented. In this study, we examine coincident measurements of water vapor, ozone, and tropospheric tracers from aircraft data taken during the Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS) aircraft campaign looking specifically for ozone depletion in regions identified as impacted by overshooting convection. Although we do find evidence of lower ozone values in air impacted by convective overshoots, using tropospheric tracers we attribute those observations to input of tropospheric air rather than catalytic ozone destruction. Additionally, we explore the consequences of these lower ozone values on surface UV, and conclude that there is minimal impact on the UV index.