Fine-scale comparison of TOMS total ozone data with model analysis of an intense Midwestern cyclone

High-resolution (similar to 40 km) along-track total column ozone data from the Total Ozone Mapping Spectrometer (TOMS) instrument are compared with a high-resolution mesoscale numerical model analysis of an intense cyclone i n the Midwestern United States. Total ozone increased by similar to 100 DU (nearly 38%) as the TOMS instrument passed over the associated tropopause f old region. Complex structure is seen in the meteorological fields and comp ares well with the total ozone observations. Ozone data support the meteoro logical analysis showing that stratospheric descent was confined to levels above similar to 600 hPa; significant positive potential vorticity at lower levels is attributable to diabatic processes. Likewise, meteorological fie lds show that two pronounced ozone streamers extending north and northeastw ard into Canada at high levels are not bands of stratospheric air feeding i nto the cyclone; one is a channel of exhaust downstream from the system, an d the other apparently previously connected the main cyclonic circulation t o a southward intrusion of polar stratospheric air and advected eastward as the cut-off cyclone evolved. Good agreement between small-scale features i n the model output and total ozone data underscores the latter's potential usefulness in diagnosing upper-tropospheric/lower-stratospheric dynamics an d kinematics.