\centerline {\bf Comparison of model analyses with TOMS total ozone data

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

Mark A. Olsen(1), William A. Gallus, Jr.(2), John L. Stanford(1) and John M. Brown(3)

(1) Department of Physics & Astronomy, Iowa State University, Ames, Iowa 50011

(2) Department of Geological & Atmospheric Sciences, Iowa State University, Ames, Iowa 50011

(3) NOAA/ERL/Forecast Systems Laboratory, Boulder, Colorado 80303

J. Geophys. Rev., 105, 20,487-20,495 (2000)


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