京津冀地区严重光化学污染时段O3的时空分布特征

利用MCCM(多尺度气象空气质量模式)对京津冀地区2008年6月严重光化学污染时段的近地面φ(NO_x)和φ(O₃)进行了模拟；同时,为了检验MCCM系统模拟φ(O₃)时空分布的能力,将模拟的气象要素、φ(NO_x)和φ(O₃)与观测数据进行了比对,并利用验证后的模拟结果对该地区严重光化学污染时段O₃时空分布特征进行研究. 结果表明:①MCCM模式可较好地反映气象场和污染物浓度场的时空分布特征. 气温、露点温度和气压的观测值与模拟值的相关系数分别为0.85、0.77和0.95；模拟的化学物种浓度的时空分布与观测结果基本相符. ②城市中心地区φ(NO_x)较高,北京和天津城市地区的φ(NO_x)甚至超过了30×10-9；京津冀平原大部分地区午后14:00φ(O₃)的最大值超过了70×10-9；而太行山沿线φ(O₃)的最大值超过了80×10-9. 结合气象要素的分析表明,午后φ(O₃)在太行山沿线的高值与气压场和流场关系密切. ③利用判断O₃生成敏感性指标——H₂O₂/HNO₃(体积分数比)分析发现,φ(O₃)日最大值和φ(总氧化剂)(总氧化剂=NO₂₊O₃)平均值的高值区域与O₃生成受NO_x和VOCs协同控制的区域极为吻合. 因此,要达到降低区域的光化学污染,应以VOCs的消减为主,同时兼顾NO_x的消减. 

Spatial-Temporal Variations of Ozone during Severe Photochemical Pollution over the Beijing-Tianjin-Hebei Region

A multi-scale meteorological and air quality modeling system was applied to the Beijing-Tianjin-Hebei region. The Multi-Scale Climate Chemistry Model (MCCM),an online-coupled atmospheric chemistry model,was used to investigate the spatial-temporal distribution of ozone (O₃) over the Beijing-Tianjin-Hebei region in June 2008. To evaluate the model performance,simulated meteorological data and air pollution data were compared with a set of observations. The spatial-temporal variations of ozone exposed to severe photochemical pollution over the Beijing-Tianjin-Hebei region was investigated with the simulated data. The results showed that the model captured the temporal and spatial variations of the meteorological and concentration fields. The correlation coefficients of the temperature,dew temperature and sea surface pressure exceeded 0.85,0.77 and 0.95,respectively. The mean NO_x concentrations were relatively high in the urban areas,especially in Beijing and Tianjin,with concentrations higher than 30×10-9. The mean O₃ concentrations at 02:00 PM were higher than 70×10-9 in most of the areas of the North China Plain. Moreover,the highest ozone concentration appeared along the Taihang Mountains,with a concentration higher than 80×10-9. The use of H₂O₂/HNO₃ as an indicator for the ozone-NO_x-hydrocarbon sensitivity indicated that the areas with higher daily maximum ozone and total oxidant (O₃₊NO₂) concentrations were in agreement with the areas in which the ozone production was controlled by NO_x and VOCs. To decrease the photochemical pollution,measures should be taken to reduce VOC emissions more than NO_x emissions in the area.