Potential Vorticity Diagnostics of Baseline and Surface Ozone in Relation to Stratospheric Intrusions and Wildfires during CABOTS 2016

An improved diagnostic technique is presented that could be applied to future air quality forecasting models to help predict days with poor air quality, and days likely to exhibit conditions for wildfire outbreak and growth. A period from late July to the middle of August 2016 was analyzed; a period of moderate to unhealthy air quality conditions were exhibited in the Sacramento non-attainment zone. Using MERRA-2 reanalysis data, a vertical cross-section analysis of 0.5 to 5.0 potential vorticity unit (PVU) was performed to analyze stratosphere-to-troposphere transport to the coastal North Bay Area site of Bodega Bay, CA and the lower Sierra Nevada Foothills site of Placerville, CA within the Sacramento non-attainment zone. During CABOTS 2016 near-daily ozonesonde launches were performed collecting a valuable dataset of baseline ozone. Ozonesonde measurements and daily changes in vertical ozone concentrations were evaluated in association with the arrival of 0.5 - 5.0 PVU within the vertical column of air quantifying values of stratospheric air masses progressing into or through the region with time. A moderately strong correlation in afternoon ozone was discovered between elevated ozonesonde measurements between 0.5 - 1.0 km vertical column above Bodega Bay and the Placerville surface ozone observations. Dates which both locales exhibited similar daily afternoon ozone increases were further evaluated. Increases in observed ozone occurred with instances of low-level stratospheric ozone transport from upper level enclosed lows located to the north and the conditions which allowed fire outbreaks and extreme fire strengthening to occur, along with a case of a strong upper level frontal passage above influencing low-level and surface ozone, and direct influence from wildfire plumes. An advancement in air quality forecasts which could predict stratospheric ozone transport to the surface would not only benefit communities, but allow forecasters and researchers to better quantify the influence of stratospheric ozone on low-level ozone pollution directly or indirectly through wildfire influence.