Spatial Pattern of 1-hour and 8-hour Daily Maximum Ozone over the OTAG Region Rudolf B. Husar CAPITA, Center for Air Pollution Impact and Trend Analysis Washington University St. Louis, Missouri

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Spatial Pattern of 1-hour and 8-hour Daily
Maximum Ozone over the OTAG RegionRudolf B.
HusarCAPITA, Center for Air Pollution Impact
and Trend AnalysisWashington UniversitySt.
Louis, Missouri
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Average summertime daily maximum ozone
concentration over the OTAG region
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Cross sectional charts of average summertime
daily maximum ozone concentration. a) South
Dakota-New England. b) Kansas-Maryland c)
Texas-N. Florida d) North-South cross section
Texas-North Dakota and Florida-E.Ohio
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Spatial pattern of 10th percentile of daily
maximum ozone
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Spatial pattern of 90th percentile of daily
maximum ozone
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Spatial pattern of 50th percentile of daily
maximum ozone
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Spatial pattern of 90th-10th percentile
difference . The figure illustrates that the
largest ozone variability is in the vicinity of
metropolitan areas
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Illustration of 8-hour moving average, 1-hour
moving average ozone concentration for Hammond, IN
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Illustration of 8-hour moving average, 1-hour
moving average ozone concentration for Greenwich,
CT
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Illustration of 8-hour moving average, 1-hour
moving average ozone concentration for Whiteface
Mountain, NY
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Scatter chart of daily maximum 8-hour and 1-hour
values, 1991-1995, June, July, and August for the
a) Northeastern OTAG region b) Southeastern OTAG
region c) Northwestern OTAG region d)
Southwestern OTAG region
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Spatial pattern for a) 1-hour exceedances (gt120
ppb) and b) 8-hour exceedances (gt102 ppb) over
the OTAG region
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Spatial pattern for a) 1-hour exceedances (gt94
ppb) and b) 8-hour exceedances (gt80 ppb) over the
OTAG region
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Spatial pattern of exceedance difference between
8-hour (gt80 ppb) and 1-hour (gt94 ppb) exceedance
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Summary and Conclusions

• The spatial pattern of daily 1-hour maximum
  summertime ozone over the OTAG region is elevated
  in the vicinity of populated metropolitan
  centers.
• A broad area of elevated ozone is also present
  over the industrial states from Illinois through
  Pennsylvania.
• The urban impact is virtually undetectable
  during clean days (10 percentile of the ozone
  concentration). However, the urban influence
  during high ozone levels (90th percentiles) is
  very pronounced, but confined to the vicinity
  (few hundred miles) of metropolitan areas.
• The overall shape of the exceedance pattern for
  8-hour and 1-hour metric is rather similar.
• Switching from the 1-hour to the 8-hour
  exceedance metric yields some increase of the
  relative (to 1-hour) exceedances over the
  industrial Midwestern states from Illinois to
  Pennsylvania and a decrease of relative
  exceedances around Houston and New York City
  where the concentrations are highly variable.