POAM Ozone Measurements and Validation in the Upper Troposphere and Lowermost Stratosphere

We provide a validation of Polar Ozone and Measurement (POAM) III ozone observations in the uppermost troposphere and lowermost stratosphere by comparison to ozone data from the Measurement of Ozone and Water Vapor by Airbus In-Service Aircraft (MOZAIC) program. The results suggest that POAM Ver.3 ozone mixing ratios in the 9-12 km region are systematically high by about 14%, consistent with POAM/ECC sonde comparisons. However, the relative variations in the POAM and MOZAIC data sets are in excellent agreement, indicating that POAM ozone measurements provide a data set suitable for studying ozone and air transport properties in the UT/LS region. Based on POAM UT/LS measurements, we are able to differentiate between tropospheric and stratospheric air parcels, and we observe a distinct seasonal cycle in ozone mixing ratios in the lowermost stratosphere during all POAM years. In the northern hemisphere high latitudes, POAM ozone mixing ratios and correlations with POAM water vapor and PV derived equivalent latitude strongly suggest that beginning in early summer air is transported from the upper troposphere at lower latitudes into the lowermost stratosphere, and that this air moves gradually poleward. In the tropopause region, POAM captures seasonal and inter-annual ozone variations, including the transition from mixing ratios typical of the upper-most troposphere, to air of stratospheric influence.