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Weekend Effect Research

Weekend Effect Research. Ozone Precursor Trends (Chapter 5.2) April 13, 2000. Ozone Precursor Trends. Objectives of trend analysis: ID response of ozone to precursor changes ID spatial & temporal changes ID changes in chemistry. Ozone Precursor Trends. Methodology:

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Weekend Effect Research

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  1. Weekend Effect Research Ozone Precursor Trends (Chapter 5.2) April 13, 2000

  2. Ozone Precursor Trends • Objectives of trend analysis: • ID response of ozone to precursor changes • ID spatial & temporal changes • ID changes in chemistry

  3. Ozone Precursor Trends • Methodology: • hrly mean CO, NOX, NO, NO2, & O3, 1980-97 • Day of Week (DOW) -- Tue-Thur = mid-week • averaged into 6 equal Periods of Day (POD) • running 3-year means

  4. Ozone Precursor Trends • ID response of ozone to precursor change • SoCAB peak ozone has declined steadily • PM ozone declined in most areas of SoCAB • ozone decline for WDs appears WEs

  5. Ozone Trends in SoCAB

  6. Ozone Trends

  7. Ozone Trends

  8. Ozone Precursor Trends • ID spatial & temporal changes • mid-day NOX trends generally similar by DOW • 4-8 a.m. NOX trend often nearly flat in 1990s • O3 DOW “crossover” in late 1980s in eastern SoCAB

  9. Ozone Precursor Trends

  10. Ozone Precursor Trends

  11. Ozone Trends

  12. Ozone Precursor Trends • ID changes in chemistry: • mid-AM NOX trend often flat but late-AM & early-PM NOX & NO2 down in 1990s • NO2 trends by DOW match NOX trends by DOW at most sites - NO2/NOX constant by DOW during late-AM & early-PM

  13. Ozone Precursor Trends

  14. Ozone Precursor Trends

  15. Ozone Precursor Trends • Initial Findings: • peak ozone down irrespective of NOX trend • ozone WE Effect much greater in 1990s than earlier but no commensurately greater NOX WE Effect • DOW “crossover” (WE > WD) has now occurred at all sites in SoCAB

  16. Ozone Precursor Trends • Recommendation: • Investigate cause of step-wise change in mid-day ozone concentrations around 1989 as it accounts for much of ozone improvement and seems stronger for WDs than WEs.

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