In Situ Measurement of Stratosperic Intrusions in the Free Troposphere and Boundary Layer During the DC3 Field Campaign

For many years, it has been known that stratospheric airmasses can become entrained within the troposphere and reach all the way down to the earth's surface. These airmasses contain high amounts of ozone and may lead to exceedences of NAAQS values at impacted surface sites. A very active region for stratosphere-to-troposphere transport (STT) is the central/western US during late winter and spring. During the DC3 field campaign, conducted over the central US in May-June 2012, evidence of STT was observed via LIDAR and satellite measurements. In situ measurement of airmasses influenced by STT often proves difficult when convection or polluted airmasses are present, as they may mask the stratospheric character of these airmasses. Here, we present a new technique for in situ detection of airmasses influenced by STT using an ensemble of long-lived halocarbons - measured aboard the NASA DC-8 aircraft by UC Irvine's whole air sampler - as tracers of stratospheric air. Using this technique, we observed evidence of STT in all three major regions of study (CO, OK, and AL), in the free troposphere, and in the boundary layer. In these samples, a significant amount of ozone was calculated to be of stratospheric origin, leading to enhancements over background levels over all altitudes studied.