Understanding Long-Term Variations in Surface Ozone in United States (U.S.) National Parks
Long-term surface ozone observations at 25 National Park Service sites across the United States were analyzed for processes on varying time scales using a time scale decomposition technique, the Ensemble Empirical Mode Decomposition (EEMD). Time scales of interest include the seasonal cycle, large-s...
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| Format: | Article |
| Language: | English |
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MDPI AG
2018-03-01
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| Series: | Atmosphere |
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| Online Access: | http://www.mdpi.com/2073-4433/9/4/125 |
| _version_ | 1811233853280354304 |
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| author | Deborah McGlynn Huiting Mao Zhaohua Wu Barkley Sive Timothy Sharac |
| author_facet | Deborah McGlynn Huiting Mao Zhaohua Wu Barkley Sive Timothy Sharac |
| author_sort | Deborah McGlynn |
| collection | DOAJ |
| description | Long-term surface ozone observations at 25 National Park Service sites across the United States were analyzed for processes on varying time scales using a time scale decomposition technique, the Ensemble Empirical Mode Decomposition (EEMD). Time scales of interest include the seasonal cycle, large-scale climate oscillations, and long-term (>10 years) trends. Emission reductions were found to have a greater impact on sites that are nearest major urban areas. Multidecadal trends in surface ozone were increasing at a rate of 0.07 to 0.37 ppbv year−1 before 2004 and decreasing at a rate of −0.08 to −0.60 ppbv year−1 after 2004 for sites in the East, Southern California, and Northwestern Washington. Sites in the Intermountain West did not experience a reversal of trends from positive to negative until the mid- to late 2000s. The magnitude of the annual amplitude (=annual maximum–minimum) decreased at eight sites, two in the West, two in the Intermountain West, and four in the East, by 5–20 ppbv and significantly increased at three sites; one in Alaska, one in the West, and one in the Intermountain West, by 3–4 ppbv. Stronger decreases in the annual amplitude occurred at a greater proportion of sites in the East (4/6 sites) than in the West/Intermountain West (4/19 sites). The date of annual maximums and/or minimums has changed at 12 sites, occurring 10–60 days earlier in the year. There appeared to be a link between the timing of the annual maximum and the decrease in the annual amplitude, which was hypothesized to be related to a decrease in ozone titration resulting from NOx emission reductions. Furthermore, it was found that a phase shift of the Pacific Decadal Oscillation (PDO), from positive to negative, in 1998–1999 resulted in increased occurrences of La Niña-like conditions. This shift had the effect of directing more polluted air masses from East Asia to higher latitudes over the North American continent. The change in the Pacific Decadal Oscillation (PDO)/El Niño Southern Oscillation (ENSO) regime influenced surface ozone at an Alaskan site over its nearly 30-year data record. |
| first_indexed | 2024-04-12T11:27:17Z |
| format | Article |
| id | doaj.art-2f414f93023940188abbeadfb01504a9 |
| institution | Directory Open Access Journal |
| issn | 2073-4433 |
| language | English |
| last_indexed | 2024-04-12T11:27:17Z |
| publishDate | 2018-03-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Atmosphere |
| spelling | doaj.art-2f414f93023940188abbeadfb01504a92022-12-22T03:35:12ZengMDPI AGAtmosphere2073-44332018-03-019412510.3390/atmos9040125atmos9040125Understanding Long-Term Variations in Surface Ozone in United States (U.S.) National ParksDeborah McGlynn0Huiting Mao1Zhaohua Wu2Barkley Sive3Timothy Sharac4Department of Chemistry, State University of New York College of Environmental Science and Forestry, Syracuse, NY 13210, USADepartment of Chemistry, State University of New York College of Environmental Science and Forestry, Syracuse, NY 13210, USADepartment of Earth, Ocean and Atmospheric Science Florida State University Tallahassee, FL 32306, USANational Park Service, Air Resources Division, Lakewood, CO 80235, USAClean Air Markets Division, United States Environmental Protection Agency, Washington, DC 20460, USALong-term surface ozone observations at 25 National Park Service sites across the United States were analyzed for processes on varying time scales using a time scale decomposition technique, the Ensemble Empirical Mode Decomposition (EEMD). Time scales of interest include the seasonal cycle, large-scale climate oscillations, and long-term (>10 years) trends. Emission reductions were found to have a greater impact on sites that are nearest major urban areas. Multidecadal trends in surface ozone were increasing at a rate of 0.07 to 0.37 ppbv year−1 before 2004 and decreasing at a rate of −0.08 to −0.60 ppbv year−1 after 2004 for sites in the East, Southern California, and Northwestern Washington. Sites in the Intermountain West did not experience a reversal of trends from positive to negative until the mid- to late 2000s. The magnitude of the annual amplitude (=annual maximum–minimum) decreased at eight sites, two in the West, two in the Intermountain West, and four in the East, by 5–20 ppbv and significantly increased at three sites; one in Alaska, one in the West, and one in the Intermountain West, by 3–4 ppbv. Stronger decreases in the annual amplitude occurred at a greater proportion of sites in the East (4/6 sites) than in the West/Intermountain West (4/19 sites). The date of annual maximums and/or minimums has changed at 12 sites, occurring 10–60 days earlier in the year. There appeared to be a link between the timing of the annual maximum and the decrease in the annual amplitude, which was hypothesized to be related to a decrease in ozone titration resulting from NOx emission reductions. Furthermore, it was found that a phase shift of the Pacific Decadal Oscillation (PDO), from positive to negative, in 1998–1999 resulted in increased occurrences of La Niña-like conditions. This shift had the effect of directing more polluted air masses from East Asia to higher latitudes over the North American continent. The change in the Pacific Decadal Oscillation (PDO)/El Niño Southern Oscillation (ENSO) regime influenced surface ozone at an Alaskan site over its nearly 30-year data record.http://www.mdpi.com/2073-4433/9/4/125ozonetrendsEnsemble Empirical Mode Decompositionannual amplitudeseasonal cycleEl Niño Southern OscillationPacific Decadal OscillationNational Park Service |
| spellingShingle | Deborah McGlynn Huiting Mao Zhaohua Wu Barkley Sive Timothy Sharac Understanding Long-Term Variations in Surface Ozone in United States (U.S.) National Parks Atmosphere ozone trends Ensemble Empirical Mode Decomposition annual amplitude seasonal cycle El Niño Southern Oscillation Pacific Decadal Oscillation National Park Service |
| title | Understanding Long-Term Variations in Surface Ozone in United States (U.S.) National Parks |
| title_full | Understanding Long-Term Variations in Surface Ozone in United States (U.S.) National Parks |
| title_fullStr | Understanding Long-Term Variations in Surface Ozone in United States (U.S.) National Parks |
| title_full_unstemmed | Understanding Long-Term Variations in Surface Ozone in United States (U.S.) National Parks |
| title_short | Understanding Long-Term Variations in Surface Ozone in United States (U.S.) National Parks |
| title_sort | understanding long term variations in surface ozone in united states u s national parks |
| topic | ozone trends Ensemble Empirical Mode Decomposition annual amplitude seasonal cycle El Niño Southern Oscillation Pacific Decadal Oscillation National Park Service |
| url | http://www.mdpi.com/2073-4433/9/4/125 |
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