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DOI | 10.3390/atmos9040125 |
Understanding Long-Term Variations in Surface Ozone in United States (US) National Parks | |
McGlynn, Deborah F.1; Mao, Huiting1; Wu, Zhaohua2; Sive, Barkley C.3; Sharac, Timothy4 | |
发表日期 | 2018-04-01 |
ISSN | 2073-4433 |
卷号 | 9期号:4 |
英文摘要 | 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 IntermountainWest 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 IntermountainWest, 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 Nina-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 Nino Southern Oscillation (ENSO) regime influenced surface ozone at an Alaskan site over its nearly 30-year data record. |
英文关键词 | ozone;trends;Ensemble Empirical Mode Decomposition;annual amplitude;seasonal cycle;El Nino Southern Oscillation;Pacific Decadal Oscillation;National Park Service |
语种 | 英语 |
WOS记录号 | WOS:000435178000011 |
来源期刊 | ATMOSPHERE |
来源机构 | 美国环保署 |
文献类型 | 期刊论文 |
条目标识符 | http://gcip.llas.ac.cn/handle/2XKMVOVA/60761 |
作者单位 | 1.SUNY Coll Environm Sci & Forestry, Dept Chem, Syracuse, NY 13210 USA; 2.Florida State Univ, Dept Earth Ocean & Atmospher Sci, Tallahassee, FL 32306 USA; 3.Natl Pk Serv, Air Resources Div, Lakewood, CO 80235 USA; 4.US EPA, Clean Air Markets Div, Washington, DC 20460 USA |
推荐引用方式 GB/T 7714 | McGlynn, Deborah F.,Mao, Huiting,Wu, Zhaohua,et al. Understanding Long-Term Variations in Surface Ozone in United States (US) National Parks[J]. 美国环保署,2018,9(4). |
APA | McGlynn, Deborah F.,Mao, Huiting,Wu, Zhaohua,Sive, Barkley C.,&Sharac, Timothy.(2018).Understanding Long-Term Variations in Surface Ozone in United States (US) National Parks.ATMOSPHERE,9(4). |
MLA | McGlynn, Deborah F.,et al."Understanding Long-Term Variations in Surface Ozone in United States (US) National Parks".ATMOSPHERE 9.4(2018). |
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