\centerline {\bf Comparison of model analyses with TOMS total ozone data</TITLE></HEAD>

<P> <H2> Evidence of stratosphere-to-troposphere transport within a
mesoscale model and TOMS total ozone </H2> </p>

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<p> <h3>Mark A. Olsen and John L.
Stanford</h3>

<p>(1) Department of Physics & Astronomy, Iowa State University, Ames, Iowa 50011</p>

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<p>
J. Geophys. Rev., submitted for publication 9/00
</p>


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<p>
<h3>Abstract</h3>
</p>

We present evidence for stratospheric mass transport into, and
remaining in, the troposphere in an intense midlatitude cyclone.
Mesoscale forecast model analysis fields from the Mesoscale Analysis
and Prediction System (MAPS) were compared with total ozone
observations from the Total Ozone Measurement Spectrometer (TOMS).
Coupled with parcel back-trajectory calculations, the analyses suggest
two mechanisms contributed to the mass exchange: (1) A region of
dynamically-induced exchange occurred on the cyclone's southern edge.
Parcels originally in the stratosphere crossed the jet core and
experienced dilution by turbulent mixing with tropospheric air.  (2)
Diabatic effects reduced parcel potential vorticity (PV) for
trajectories traversing precipitation regions, resulting in a
``PV-hole'' signature in the cyclone center.  Air with
lower-stratospheric values of ozone and water vapor was left in the
troposphere.  The strength of the latter process may be atypical.
These results, combined with other research, suggest that
precipitation-induced diabatic effects can significantly modify
(either decreasing or increasing) parcel potential vorticity,
depending on parcel trajectory configuration with respect to jet core
and maximum heating regions.  In addition, these results underscore
the importance of using not only PV but also chemical constituents for
diagnoses of stratosphere-troposphere exchange (STE).

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