Local and synoptic meteorological influences on daily variability in summertime surface ozone in eastern China

Abstract

Abstract. Ozone pollution in China is influenced by meteorological processes on multiple scales. Using regression analysis and weather classification, we statistically assess the impacts of local and synoptic meteorology on daily variability in surface ozone in eastern China in summer during 2013–2018. In this period, summertime surface ozone in eastern China (20–42∘ N, 110–130∘ E) is among the highest in the world, with regional means of 73.1 and 114.7 µg m−3, respectively, in daily mean and daily maximum 8 h average. Through developing a multiple linear regression (MLR) model driven by local and synoptic weather factors, we establish a quantitative linkage between the daily mean ozone concentrations and meteorology in the study region. The meteorology described by the MLR can explain ∼43 % of the daily variability in summertime surface ozone across eastern China. Among local meteorological factors, relative humidity is the most influential variable in the center and south of eastern China, including the Yangtze River Delta and the Pearl River Delta regions, while temperature is the most influential variable in the north, covering the Beijing–Tianjin–Hebei region. To further examine the synoptic influence of weather conditions explicitly, six predominant synoptic weather patterns (SWPs) over eastern China in summer are objectively identified using the self-organizing map clustering technique. The six SWPs are formed under the integral influence of the East Asian summer monsoon, the western Pacific subtropical high, the Meiyu front, and the typhoon activities. On average, regionally, two SWPs bring about positive ozone anomalies (1.1 µg m−3 or 1.7 % and 2.7 µg m−3 or 4.6 %), when eastern China is under a weak cyclone system or under the prevailing southerly wind. The impact of SWPs on the daily variability in surface ozone varies largely within eastern China. The maximum impact can reach ±8 µg m−3 or ±16 % of the daily mean in some areas. A combination of the regression and the clustering approaches suggests a strong performance of the MLR in predicting the sensitivity of surface ozone in eastern China to the variation of synoptic weather. Our assessment highlights the importance of meteorology in modulating ozone pollution over China.

2013–2019 increases of surface ozone pollution in China: anthropogenic and meteorological influences

“…Similar to our previous study for 2013-2017(Li et al, 2019a, the most important meteorological predictor variables in the MLR model are daily maximum temperature for the NCP and meridional wind at 850 hPa for the PRD. These dominant meteorological parameters are also consistent with the findings from other studies (Gong and Liao, 2019;Wang et al, 2019;Han et al, 2020). Hot weather is the main meteorological driver for the NCP, and we will elaborate on this in the next section.…”

“…On the other hand, we find that meteorology mitigated ozone pollution increases over western China, northeastern China, and the Shandong Peninsula. Summer ozone in the Shandong Peninsula is strongly affected by maritime inflow (J. Zhang et al, 2019;Han et al, 2020) which increased over the 2013-2019 period ( Figure S1).…”

Surface Ozone‐Meteorology Relationships: Spatial Variations and the Role of the Jet Stream

“…Poleward of the midlatitudes, the strength of r(T, O 3 ) decreases nearly monotonically over land, reaching either weak values or significantly negative correlations (Figure 3a). The O 3 -temperature relationship is varied equatorward of the midlatitudes; but, in the zonal mean, r(T, O 3 ) decreases to negative values south of 30 • N. Previous work by Rasmussen et al (2012) and Brown-Steiner et al (2015) in the United States and Han et al (2020) and Lu, Zhang, Chen, et al (2019) in China showed a similar latitudinal gradient of r(T, O 3 ). Despite the general tendency of a positive-to-negative relationship between O 3 and temperature with decreasing latitude, there are regions at low latitudes with significant positive correlations between O 3 and temperature (Central America, Sahel, the south coast of the Arabian Peninsula, Indo-Gangetic Plain; Figure 3a).…”

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

“…Furthermore, the RH presents a good correlation with the EOF1 time series (R = 0.59). Han et al (2020) also found that RH is the most important factor affecting O3 in the YRD. However, it is still unclear how the change in different weather systems causes the variation in RH, and how the RH variation impacts the other meteorological factors and O3 accumulation.…”

“…3b, RH is the most crucial factor and its variation is similar to the variation in the total meteorological impact. Han et al (2020) also found that RH is the most influential factor in the central and south parts of eastern China. The East Asian summer monsoon plays a key role in affecting the local RH, and meanwhile it might bring a certain amount of O3 from the south area.…”