Quantifying the impact of synoptic circulation patterns on ozone variability in northern China from April to October 2013–2017

Abstract

Abstract. The characteristics of ozone variations and the impacts of synoptic and local meteorological factors in northern China were quantitatively analyzed 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 yr−1, and the three most polluted months were closely related to the variations in the synoptic circulation patterns, which occurred in June (149 µg m−3), May (138 µg m−3) and July (132 µg m−3). A total of 26 weather types (merged into five weather categories) were objectively identified using the Lamb–Jenkinson method. The highly polluted weather categories included the S–W–N directions (geostrophic wind direction diverts from south to north), low-pressure-related weather types (LP) and cyclone type, which the study area controlled by a low-pressure center (C), and the corresponding domain-averaged MDA8 O3 concentrations were 122, 126 and 128 µg m−3, respectively. Based on the frequency and intensity changes of the synoptic circulation patterns, 39.2 % of the interannual increase in the domain-averaged O3 from 2013 to 2017 was attributed to synoptic changes, and the intensity of the synoptic circulation patterns was the dominant factor. Using synoptic classification and local meteorological factors, the segmented synoptic-regression approach was established to evaluate and forecast daily ozone variability on an urban scale. The results showed that this method is practical in most cities, and the dominant factors are the maximum temperature, southerly winds, relative humidity on the previous day and on the same day, and total cloud cover. Overall, 41 %–63 % of the day-to-day variability in the MDA8 O3 concentrations was due to local meteorological variations in most cities over northern China, except for two cities: QHD (Qinhuangdao) at 34 % and ZZ (Zhengzhou) at 20 %. Our quantitative exploration of the influence of both synoptic and local meteorological factors on interannual and day-to-day ozone variability will provide a scientific basis for evaluating emission reduction measures that have been implemented by the national and local governments to mitigate air pollution in northern China.

Dynamic Processes Dominating Ozone Variability in Warm Seasons of 2014–2018 over the Yangtze River Delta Region, China

“…In addition, the SWP change includes both frequency and intensity changes. We find that the frequency change in SWPs has less impact on the inter-annual variation in O3 levels than the intensity change in SWPs, which is consistent with the results of Hegarty et al (2007) and Liu et al (2019). The contribution of intensity change and frequency change will be further discussed in section 3.4.…”

“…We further reconstructed the EOF1 time series by considering different SWPIIs due to the unique characteristics of each SWP. The results are better than those in Hegarty et al (2007) and Liu et al (2019) who used the same SWPIIs in all SWPs.…”

“…Hegarty et al (2007) used the domain averaged sea level pressure to represent the circulation intensity index (CII). Liu et al (2019) reconstructed the inter-annual O3 level in the northern China using the center pressure of the lowest pressure system. But we find the intensity variation in each SWP is different when O3 increases.…”

“…especially in the YRD. For the northern China and the PRD region, Liu et al (2019) quantified the impact of synoptic circulation patterns on O3 variability in the northern China from April to October during 2013-2017. Yang et al (2019) quantitatively assessed the impacts of meteorological factors and the precursor emissions on the long-term trend of ambient O3 over the PRD region.…”

Long-Term (2005–2017) View of Atmospheric Pollutants in Central China Using Multiple Satellite Observations

“…The precursors of O3 included NOx and VOCs, but there was also a notable rise in O3, as NO2 decreased in 2014-2016. Considering the nonlinear relationship between O3 and its precursors, the decrease of NO2 in high NOx/VOC ratio conditions promoted O3 formation [37]. In addition, it was found that the large reduction of aerosol loading enhanced O3 production rate to stronger photolysis [38].…”