珠三角秋季典型气象条件对空气污染过程的影响分析

利用空气质量指数(AQI)、主要大气污染物浓度和气象要素、天气图等数据资料,结合中尺度数值天气预报模式WRF,对2014年10月珠三角地区污染期间的天气形势及气象特征进行了分析.结果表明,WRF模式可以较好地反映珠三角地区主要城市地面和高空气象要素的时空变化,9个城市平均地表的温度、相对湿度和风速的模拟值与观测值的相关系数分别为0.90、0.87和0.78.对2014年10月3次污染过程的分析表明,造成该时段珠三角地区空气污染的天气形势主要是高压底部型和均压场型.静风或小风(2 m·s~(-1))及稳定的大气层结均不利于污染物的扩散,同时由于偏北气流输送周边污染物到珠三角地区,导致污染物浓度不断增加.相对湿度低于65%时,珠三角地区首要污染物以O_3为主;相对湿度高于70%时,PM_(2.5)浓度逐渐增加,成为主要污染物.高温等气象条件会影响光化学反应,加重珠江三角洲的空气污染,表现了该地区大气复合污染的特性.

Impact of typical meteorological conditions on air pollution over Pearl River Delta in autumn

Through analyzing the observed air quality index (AQI), pollutant concentrations, meteorological observations, synoptic charts and the WRF mesoscale numerical weather prediction results together, the impacts of weather conditions and meteorological characteristics on air pollution over the Pearl River Delta in October 2014 were investigated. Comparison with observations showed that WRF was able to reproduce temporal and spatial variations of ground-level and upper meteorological elements, with the correlation coefficient between simulated and observed average surface temperature, relative humidity and wind speed at nine cities of 0.90, 0.87 and 0.78, respectively. Analysis of all three pollution episodes in October showed that the bottom of the high-pressure control type and uniform pressure control type are the main meteorological factors of air pollution in the PRD. Low wind speed (<2 m·s^-1) and pollutant transport along with the northerly wind led to the increase of the pollutant concentrations in the PRD. In addition, O₃ was the primary pollutant when the relative humidity (RH) was lower than 65%, while PM_2.5 became the primary pollutant when the RH was higher than 70%. The photochemical reaction during high temperature conditions also caused the increase of air pollution in the PRD.