Probing Troposphere Ozone Variations during Stratospheric Intrusions Using MERRA-2, Potential Vorticity, and CABOTS Ozonesonde Measurements

This research uses ozone and meteorological data collected during the California Baseline Ozone Transport Study (CABOTS) in the summer of 2016, along with MERRA-2 Potential Vorticity (PV) reanalysis data, to gain a greater understanding of stratospheric ozone influence in the lower troposphere. During CABOTS, near daily ozonesondes were launched off the coast of Bodega Bay, CA from the middle of May to the middle of August. A complete understanding of stratospheric ozone and how it influences lower tropospheric ozone concentrations is key in improving the accuracy of air quality models. Surface ozone concentrations greater than 70 ppb, the 8-hour standard in California, is considered unhealthy for humans and the environment. Therefore, cases where the vertical ozone concentration profile have peaks in the lower troposphere exceeding 70 ppb were picked for further analysis. For said cases, PV is analyzed, starting 2 days prior to the event, the day of the event, and the 2 days that followed the event. This gives an indication of stratospheric air, rich in high ozone levels, being introduced into the lower troposphere, and potentially polluting the planetary boundary layer. This study begins to fill a gap in knowledge by quantifying how lower level ozone concentrations change before, during and after a stratospheric intrusion event.