Integrated studies of a regional ozone pollution synthetically affected by subtropical high and typhoon system in the Yangtze River Delta region, China

Abstract

Abstract. Severe high ozone (O 3 ) episodes usually have close relations to synoptic systems. A regional continuous O 3 pollution episode was detected over the Yangtze River Delta (YRD) region in China during 7-12 August 2013, in which the O 3 concentrations in more than half of the cities exceeded the national air quality standard. The maximum hourly concentration of O 3 reached 167.1 ppb. By means of the observational analysis and the numerical simulation, the characteristics and the essential impact factors of the typical regional O 3 pollution are comprehensively investigated. The observational analysis shows that the atmospheric subsidence dominated by the western Pacific subtropical high plays a crucial role in the formation of high-level O 3 . The favorable weather conditions, such as extremely high temperature, low relative humidity and weak wind speed, caused by the abnormally strong subtropical high are responsible for the trapping and the chemical production of O 3 in the boundary layer. In addition, when the YRD cities are at the front of Typhoon Utor, the periphery circulation of typhoon system can enhance the downward airflows and cause worse air quality. However, when the typhoon system weakens the subtropical high, the prevailing southeasterly surface wind leads to the mitigation of the O 3 pollution. The integrated process rate (IPR) analysis incorporated in the Community Multi-scale Air Quality (CMAQ) model is applied to further illustrate the combined influence of subtropical high and typhoon system in this O 3 episode. The results show that the vertical diffusion (VDIF) and the gas-phase chemistry (CHEM) are two major contributors to O 3 formation. During the episode, the contributions of VDIF and CHEM to O 3 maintain the high values over the YRD region. On 10-12 August, the cities close to the sea are apparently affected by the typhoon system, with the contribution of VDIF increasing to 28.45 ppb h −1 in Shanghai and 19.76 ppb h −1 in Hangzhou. In contrast, the cities far away from the sea can hardly be affected by the periphery circulation of typhoon system. When the typhoon system significantly weakens the subtropical high, the contribution values of all individual processes decrease to a low level in all YRD cities. These results provide an insight for the O 3 pollution synthetically impacted by the western Pacific subtropical high and the tropical cyclone system.

Regional severe particle pollution and its association with synoptic weather patterns in the Yangtze River Delta region, China

“…In recent years, similar to other megacity clusters in China, such as the Beijing-Tianjin-Hebei (BTH) region (He et al, 2001;Chan and Yao, 2008;Ji et al, 2012;Zhao et al, 2013;Zheng et al, 2015a) and the Pearl River Delta (PRD) region (Ho et al, 2003;Chan and Yao, 2008;Xie et al, 2016c;Zhu et al, 2017), the YRD has suffered from severe air pollution problems caused by an increasing population, urban expansion, and industrialization (Chan and Yao, 2008;Fu et al, 2008Fu et al, , 2010Fu et al, , 2014Deng et al, 2011;Li et al, 2011;Huang et al, 2012;Kang et al, 2013;Wang et al, 2013Wang et al, , 2014Wang et al, , 2015Xie et al, 2014Xie et al, , 2016aXie et al, , b, 2017Feng et al, 2015;Zheng et al, 2015b;Shu et al, 2016;Xu et al, 2016;Ming et al, 2017). In particular, severe particle pollution episodes are widely recognized as one of the major air pollution issues in the YRD (Fu et al, 2008(Fu et al, , 2010Deng et al, 2011;Huang et al, 2012;Kang et al, 2013;Kong et al, 2013;Wang et al, 2013Wang et al, , 2014Wang et al, , 2015Fu et al, 2014;Feng et al, 2015;…”

“…The Yangtze River Delta (YRD) region, which is located in the southeastern coastal area of East China, is one of the most developed urban economic regions in the world; it generally includes Shanghai, Jiangsu Province and Zhejiang Province, and it occupies over 20 % of China's total gross domestic product (Shu et al, 2016;Xie et al, 2016aXie et al, , 2017. In recent years, similar to other megacity clusters in China, such as the Beijing-Tianjin-Hebei (BTH) region (He et al, 2001;Chan and Yao, 2008;Ji et al, 2012;Zhao et al, 2013;Zheng et al, 2015a) and the Pearl River Delta (PRD) region (Ho et al, 2003;Chan and Yao, 2008;Xie et al, 2016c;Zhu et al, 2017), the YRD has suffered from severe air pollution problems caused by an increasing population, urban expansion, and industrialization (Chan and Yao, 2008;Fu et al, 2008Fu et al, , 2010Fu et al, , 2014Deng et al, 2011;Li et al, 2011;Huang et al, 2012;Kang et al, 2013;Wang et al, 2013Wang et al, , 2014Wang et al, , 2015Xie et al, 2014Xie et al, , 2016aXie et al, , b, 2017Feng et al, 2015;Zheng et al, 2015b;Shu et al, 2016;Xu et al, 2016;Ming et al, 2017).…”

Impacts of emission reduction and meteorological conditions on air quality improvement during the 2014 Youth Olympic Games in Nanjing, China

“…For all domains, 23 vertical sigma layers from the surface to the top pressure of 100 hpa were set, with about 10 layers in the planetary boundary layer. The detailed dynamic parameterization in WRF as well as the physical and chemical schemes of CMAQ applied in this research were the same as those in Shu et al (2016)'s work and were proven to have good performance. As for the innermost domain, Nanjing Environmental Protection Bureau chooses the local nine state-controlled air-monitoring sites (see Fig.…”

“…It incorporates a set of up-to-date compatible modules and control equations for the atmosphere and can fully consider complicated physical and chemical processes (Byun and Schere, 2006;Foley et al, 2010). Many applications have proven that CMAQ is a reliable tool for simulating air quality from city scale to mesoscale (Xing et al, 2011;Dong et al, 2013;Liu et al, 2013;Xu et al, 2013;Shu et al, 2016). The Community Multiscale Air Quality (CMAQ v4.7.1, Binkowski and Roselle, 2003) model includes the 2005 Carbon Bond gas-phase mechanism (CB05) (Yarwood et al, 2005) and the fourth-generation CMAQ Figure 1.…”

“…Weather Research and Forecasting (WRF) is a new generation of mesoscale weather forecast model and assimilation system, developed by the National Center for Atmospheric Research (NCAR). It has been widely applied in China and shows a good performance in all kinds of weather forecasts (Jiang et al, 2008(Jiang et al, , 2012Xu et al,2013;Liao et al, 2014Liao et al, , 2015Xie et al, 2014Xie et al, , 2016Li et al, 2016;Shu et al, 2016). The WRF v3.2.1 (Skamarock et al, 2008) model was run to provide meteorological fields for CMAQ.…”