2019年9月海南省持续臭氧污染天气的气象条件分析

Meteorological conditions for the persistent ozone polluted event over Hainan Province in September 2019

2019年9月海南省(三沙市除外)发生了一次持续时间长、发生范围广的臭氧(ozone,O_(3))污染事件.本文利用环境监测资料、气象观测数据和FNL再分析资料,从O_(3)污染概况、大气环流背景和O_(3)污染天气演变过程的3个方面,探讨了气象条件在此次持续性O_(3)污染过程中的作用.结果表明,污染时段(21—30日)的全省平均O_(3)最大8 h平均浓度(O_(3)−8 h)为146.3μg·m^(−3),平均每天有6.3个市县的O_(3)-8 h浓度超标,其中28日超标市县达到12个,海口市O_(3)−8 h浓度超标持续的时间最长(9 d).污染时段海南省受副高内部下沉气流影响,天气形势稳定.低层水平风速辐合,气象因子的垂直分布有助于增大混合层的湍流混合作用,这些气象背景场为O_(3)污染的维持和发展提供了有利的气象条件.9月海南省日降水量、相对湿度和平均风速在逐日减小,而气压和日照时数在逐渐增加,平均气温维持在24℃以上,关键气象因子的变化特征有利于促进光化学反应速率,致使O_(3)浓度维持较高水平.多元线性回归结果表明,关键气象因子回归的O_(3)−8 h浓度与观测得到的O_(3)−8 h浓度有较好的一致性,二者的相关系数高达0.93,通过了99.9%的信度检验,回归值对实测值的方差贡献达到0.86.

In September 2019,a long-lasting and wide-ranging ozone(O_(3))polluted event occurred in Hainan Province(except Sansha City).Using the environmental monitoring data,meteorological observation data and FNL reanalysis data,this study reveals the role of meteorological conditions in this long-persisting O_(3)pollution process,including the O_(3)polluted degree,atmospheric circulation background field and weather evolution of O_(3)pollution.The results show that the maximum 8haveraged concentration of O_(3)(O_(3)−8 h)reached 146.3μg·m^(−3) in the polluted period(21—30 September),about 6.3 cities and counties exceeding the polluted standard of O_(3)−8 h concentration every day in average during the polluted period.The maximum number of the polluted cities and counties reached to 12 on 28 September.Moreover,the longest polluted period(9 d)appeared in Haikou City.During the polluted period,Hainan Province was affected by the sinking airflow inside the subtropical high,with a stable weather condition.Low-level horizontal wind speed convergence and the vertical distribution of meteorological factors helps to increase the turbulent mixing of the mixed layer.The above meteorological fields provide favorable background for the maintenance and development of O_(3)pollution in Hainan Province.In addition,the daily precipitation,relative humidity,and average wind speed are decreasing,while the pressure and sunshine duration are gradually increasing day by day in September,and the average temperature is above 24℃in Hainan Province.These key meteorological factors are conducive to the increase of the photochemical reaction rate,and result in the O_(3)concentration maintained at a high level.Furthermore,the results from the multiple linear regression show that O_(3)−8 h concentration regressed by the key meteorological factors is in good agreement with the observed O_(3)−8 h concentration,with a high correlation coefficient(0.93),exceeding the 99.9%confidence level.The variance contribution of the regression value reaches to 0.86.