title: Simulation of ozone formation at different elevations in mountainous area of Hong Kong using WRF-CMAQ model.
abstract: Field measurements were simultaneously conducted at a mountain (Mt.) site (Tai Mao Shan, TMS) and an urban site (Tsuen Wan, TW) at the foot of the Mt. TMS in Hong Kong. An interesting event with consecutive high-ozone (O₃) days from 08:00 on 28 Oct. to 23:00 on 03 Nov., 2010 was observed at Mt. TMS, while no such polluted event was found at the foot of the mountain. The Weather Research and Forecasting (WRF)-Community Multiscale Air Quality (CMAQ) models were used to understand this event. Model performance evaluation showed that the simulated meteorological parameters and air pollutants were well in agreement with the observations. The index of agreement (IOA) of temperature, relative humidity, wind direction and wind speed were 0.93, 0.83, 0.46 and 0.60, respectively. The multi-day high O₃ episode at Mt. TMS was also reasonably reproduced (IOA=0.68). Horizontally, the photochemical processes determined the O₃ levels in southwestern Pearl River Delta (PRD) and the Pearl River Estuary (PRE), while in eastern and northern PRD, the O₃ destruction was over the production during the event. Vertically, higher O₃ values at higher levels were found at both Mt. TMS and TW, indicating a vertical O₃ gradient over Hong Kong. With the aid of the process analysis module, we found positive contribution of vertical transport including advection and diffusion to O₃ mixing ratios at the two sites, suggesting that O₃ values at lower locations could be affected by O₃ at higher locations via vertical advection and diffusion over Hong Kong.
authors.affiliation: Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hong Kong; Shenzhen Research Institute, The Hong Kong Polytechnic University, Hong Kong.
authors.forename: N
authors.initials: N
authors.lastname: Wang
authors.affiliation: Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hong Kong; Shenzhen Research Institute, The Hong Kong Polytechnic University, Hong Kong. Electronic address: ceguohai@polyu.edu.hk.
authors.forename: H
authors.initials: H
authors.lastname: Guo
authors.affiliation: International Institute for Earth System Science, Nanjing University, China. Electronic address: jiangf@nju.edu.cn.
authors.forename: F
authors.initials: F
authors.lastname: Jiang
authors.affiliation: Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hong Kong; Shenzhen Research Institute, The Hong Kong Polytechnic University, Hong Kong; Department of Atmospheric Science, School of Environmental Science and Engineering, Sun Yat-Sen University, Guangzhou, China.
authors.forename: Z H
authors.initials: ZH
authors.lastname: Ling
authors.affiliation: Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hong Kong.
authors.forename: T
authors.initials: T
authors.lastname: Wang
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D000397:Air Pollution / Q000706:statistics & numerical data*; D004784:Environmental Monitoring / Q000379:methods*; D005544:Forecasting; D006723:Hong Kong; D008956:Models, Chemical; D010126:Ozone / Q000032:analysis*; D052638:Particulate Matter / Q000032:analysis; D012621:Seasons; D014887:Weather
chemical_list: D000393:Air Pollutants; D052638:Particulate Matter; D010126:Ozone
keywords: CMAQ; Gas-phase chemistry; Ozone episode; Vertical ozone gradient; Vertical transport