Evidence of stratosphere-to-troposphere transport within a mesoscale modeland Total Ozone Mapping Spectrometer total ozone

We present evidence for stratospheric mass transport into, and remaining in , the troposphere in an intense midlatitude cyclone. Mesoscale forecast mod el analysis fields from the Mesoscale Analysis and Prediction System were c ompared with total ozone observations from the Total Ozone Measurement Spec trometer. Coupled with parcel back trajectory calculations, the analyses su ggest that two mechanisms contributed to the mass exchange: (1) A region of dynamically induced exchange occurred on the cyclone's southern edge. Parc els originally in the stratosphere crossed the jet core and experienced dil ution by turbulent mixing with tropospheric air. (2) Diabatic effects reduc ed parcel potential vorticity (PV) for trajectories traversing precipitatio n regions, resulting in a "PV hole" signature in the cyclone center. Air wi th values of ozone and water vapor typical of the lower stratosphere was le ft in the troposphere. The strength of the latter process may be atypical. These results, combined with other research, suggest that precipitation-ind uced diabatic effects can significantly modify (either decreasing or increa sing) parcel potential vorticity, depending on parcel trajectory configurat ion with respect to jet core and maximum heating regions. The diabatic heat ing effect on stratosphere-troposphere exchange (STE) is more important to tropopause erosion than to altering parcel trajectories. In addition, these results underscore the importance of using not only PV but also chemical c onstituents for diagnoses of STE.