Elucidating the ozone pollution in Yangtze River Delta region during the 2016 G20 summit for MICS-Asia III

Abstract

<p><strong>Abstract.</strong> To elucidate the factors governing urban ozone (O<sub>3</sub>) pollution during the campaign of G20 summit in 2016 Hangzhou, China, the Weather Research Forecast with Chemistry (WRF-Chem) model was used to simulate the spatial and temporal O<sub>3</sub> evolution in the Yangtze River Delta (YRD) region from 24 August to 6 September 2016. Various atmospheric processes were analyzed to determine the influential factors of ozone formation through integrated process rate method. The results indicated that both the vertical diffusion and the enhanced process of local chemical generation accounted for the increase of surface O<sub>3</sub> concentration in Hangzhou. Local chemical generation was found to positively correlated with O<sub>3</sub> concentrations, with correlation coefficient of 0.77. In accordance with the tropical weather cycle, subsidence air and stagnant weather were induced. Dynamic circulations of O<sub>3</sub> through advection were associated with the urban heat island effect. All these factors intensified ozone pollution in Hangzhou, particularly on 25 August 2016 (O<sub>3</sub>-8 h: 98 ppb). These findings provide insight into urban O<sub>3</sub> formation and dispersion during tropical cyclone events, and support the Model Intercomparison Study Asia Phase III (MICS-Asia Phase III).</p>