Publication Date:
2019-06-07
Description:
The ozone variation characteristics and the impact of synoptic and local meteorological factors in North China were analysed quantitively during the warm season from 2013 to 2017 based on multi-city, in-situ ozone and meteorological data, as well as meteorological reanalysis. The domain-averaged maximum daily 8-h running average O3 (MDA8 O3) concentration was 122 ± 11 μg m−3 with an increase rate of 7.88 μg m−3 year−1, and the three most highly-polluted months were June (149 μg m−3), May (138 μg m−3) and July (132 μg m−3), which was closely related to synoptic circulation variations. Twenty-six synoptic circulation types (merged into 5 weather categories) were objectively identified using the Lamb-Jenkinson method. The highly-polluted weather categories included S-W-N directions, LP (low-pressure related circulation patterns) and C (cyclone type), and corresponding domain-averaged MDA8 O3 concentration were 122, 126 and 128 μg m−3, respectively. Based on the frequency and intensity changes of synoptic circulations, 39.2 % of the inter-annual domain-averaged O3 increase from 2013 to 2017 was attributed to synoptic changes, and intensity of synoptic circulations was the dominant factor. Using synoptic classification and local meteorological factors, the segmented synoptic-regression approach was established to evaluate and forecast daily ozone variations on an urban scale. The results showed that this method is practicable in most cities, and that the dominant factors are the maximum temperature, southerly winds, relative humidity in the previous and in the same day, and total cloud cover. Overall, 43–64 % of the day-to-day variability of MDA8 O3 concentrations was due to local meteorological variations in most cities over North China, except for QHD~32 % and ZZ~25 %. Our quantitative exploration on synoptic and local meteorological factors influencing both on inter-annual and day-to-day ozone variations will provide the scientific basis for evaluating emission reduction measures, since the national and local governments have implemented a series of measures to mitigate air pollution in North China in these five years.
Electronic ISSN:
1680-7375
Topics:
Geosciences
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