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- Title
Influence of synoptic patterns on surface ozone variability over the Eastern United States from 1980 to 2012.
- Authors
Shen, L.; Mickley, L. J.; Tai, A. P. K.
- Abstract
We investigate the effect of synoptic-scale weather patterns on observed maximum daily 8 h average (MDA8) surface ozone over the eastern United States during 1980-2012 in summer (June-August, JJA). Zonally averaged, the SD of daily MDA8 JJA ozone shows a bimodal structure, with peaks at 30-35° N and 39-43° N, identifying those regions most influenced by daily weather variability. We apply Empirical Orthogonal Functions (EOFs) to understand the causes of this structure. The first three leading EOF patterns explain 53% of the total variance in deseasonalized surface ozone, displaying (1) a widespread decrease of ozone in the eastern United States associated with southward movement of jet wind, (2) a north-south pattern linked to the Bermuda High system when its west boundary is located along the East coast, and (3) an east-west pattern characteristic of a westward extension of Bermuda High and an enhanced Great Plains low level jet (GPLLJ). The northern peak of ozone SD can be explained by polar jet activity, while the southern peak appears related to variability in the Bermuda High and GPLLJ. In the Midwest and Northeast, we find that the correlation coefficient r between detrended mean JJA MDA8 ozone and the polar jet frequency ranges between -0.76 and -0.93 over 1980-2012 depending on the time period selected, suggesting that polar jet frequency could provide a simple metric to predict ozone variability in future climate regimes. In the Southeast, the influence of the Bermuda High on mean JJA MDA8 ozone depends on the location of its west edge. For those summers when the average position of the west edge is located west of ~ 85.4° W, a westward shift in the Bermuda High west edge increases ozone in the Southeast by ~ 1 ppbv deg-1 in longitude. For all summers, a northward shift in the Bermuda High west edge increases ozone over the entire eastern United States by 1-2 ppbv deg-1 in latitude. None of the synoptic patterns identified in this study show a significant trend from 1980 to 2012, confirming that the observed ozone decrease over the eastern United States during this time period is mainly caused by emission controls.
- Subjects
EAST (U.S.); BERMUDA Islands; SYNOPTIC meteorology; OZONE; ORTHOGONAL functions; EMPIRICAL research
- Publication
Atmospheric Chemistry & Physics Discussions, 2015, Vol 15, Issue 9, p13073
- ISSN
1680-7367
- Publication type
Article
- DOI
10.5194/acpd-15-13073-2015