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The NOAA GOES-8 Sounder ozone product above shows a lobe of high total column ozone concentration (350-375 Dobson Units, green enhancement) associated with a progressive shortwave trough (06 UTC | 12 UTC | 18 UTC) which was propagating eastward across the northcentral U.S. and the Great Lakes region on 29 September 1999.
The image shown below is the daily composite of total ozone from the Earth Probe TOMS on 29 September 1999. The lobe of high total column ozone noted on the GOES ozone product is also evident on the TOMS data. The hourly temporal resolution from GOES allows better monitoring of the evolution and movement of this ozone feature, especially during local nighttime (when the TOMS instrument is unable to provide ozone data).