Ozone column measurements, annual averages, US sites

Description: This is data from five U.S. sites (including the average of the five sites) as follows:

• Caribou, Maine, 46.9° N (dark green)
• Bismark, North Dakota, 46.8° N (brown)
• Nashville, Tennessee, 36.2° N (magenta)
• average of listing US sites (red)
• Boulder, Colorado, 40.0° N (light green)
• Mauna Loa, Hawaii, 19.5° N (blue)

Comments: The graph indicates the following:

• Significant differences in average ozone column between locations, exceeding 15% for these sites (trend is for greater values further from the equator);
• Significant year-to-year variation, up to 5%;
• An overall decrease of about 5%, with most of this decrease after 1980;
• Three sites recording the lowest annual average in 1993, with all sites showing an increase from 1993 to 1998.

Source:

© 2001, 2002 by Wm. Robert Johnston.
Last modified 26 December 2002.
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