Abstract
Abstract. Regional air pollution is significantly associated with dominant weather systems. In this study, the relationship between the particle pollution over the Yangtze River Delta (YRD) region and weather patterns is investigated. First, the pollution characteristics of particles in the YRD are studied using in situ monitoring data (PM2.5 and PM10) in 16 cities and Terra/MODIS AOD (aerosol optical depth) products collected from December 2013 to November 2014. The results show that the regional mean value of AOD is high in the YRD, with an annual mean value of 0.71±0.57. The annual mean particle concentrations in the cities of Jiangsu Province all exceed the national air quality standard. The pollution level is higher in inland areas, and the highest concentrations of PM2.5 and PM10 are 79 and 130 µg m−3, respectively, in Nanjing. The PM2.5 : PM10 ratios are typically high, thus indicating that PM2.5 is the overwhelmingly dominant particle pollutant in the YRD. The wintertime peak of particle concentrations is tightly linked to the increased emissions during the heating season as well as adverse meteorological conditions. Second, based on NCEP (National Center for Environmental Prediction) reanalysis data, synoptic weather classification is conducted and five typical synoptic patterns are objectively identified. Finally, the synthetic analysis of meteorological fields and backward trajectories are applied to further clarify how these patterns impact particle concentrations. It is demonstrated that air pollution is more or less influenced by high-pressure systems. The relative position of the YRD to the anti-cyclonic circulation exerts significant effects on the air quality of the YRD. The YRD is largely influenced by polluted air masses from the northern and the southern inland areas when it is located at the rear of the East Asian major trough. The significant downward motion of air masses results in stable weather conditions, thereby hindering the diffusion of air pollutants. Thus, this pattern is quite favorable for the accumulation of pollutants in the YRD, resulting in higher regional mean PM10 (116.5 ± 66.9 µg m−3), PM2.5 (75.9 ± 49.9 µg m−3), and AOD (0.74) values. Moreover, this pattern is also responsible for the occurrence of most large-scale regional PM2.5 (70.4 %) and PM10 (78.3 %) pollution episodes. High wind speed and clean marine air masses may also play important roles in the mitigation of pollution in the YRD. Especially when the clean marine air masses account for a large proportion of all trajectories (i.e., when the YRD is affected by the cyclonic system or oceanic circulation), the air in the YRD has a lesser chance of being polluted. The observed correlation between weather patterns and particle pollution can provide valuable insight into making decisions about pollution control and mitigation strategies.
Highlights
The common occurrence of regional particle pollution has acquired worldwide attention in the scientific community (Malm et al, 1994; Putaud et al, 2004; Chan and Yao, 2008) due to its adverse impacts on visibility (Singh and Dey, 2012; Green et al, 2012) and public health (Kappos et al, 2004; Brook et al, 2010)
The peak particle concentrations are observed in winter, the above results demonstrate that the maximum regional mean aerosol optical depth (AOD) values occur in summer, as they reach their highest value of 1.60 in June
This result is similar to that found by Kim et al (2006), who reported that the value of AOD is associated with the pollution levels of fine www.atmos-chem-phys.net/17/12871/2017/
Summary
The common occurrence of regional particle pollution has acquired worldwide attention in the scientific community (Malm et al, 1994; Putaud et al, 2004; Chan and Yao, 2008) due to its adverse impacts on visibility (Singh and Dey, 2012; Green et al, 2012) and public health (Kappos et al, 2004; Brook et al, 2010). Zheng et al (2015b) summarized the synoptic-scale atmospheric circulations influencing the distribution of particles over eastern China during autumn from 2001 to 2010 They found that there are six polluted weather types and three clean ones and revealed that heavy pollution events most commonly occur when the study areas are located at the rear of the anticyclone.
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