大连市冬季大气污染数值模拟及其对人工增雨(雪)作业的指示作用

Simulation and analysis of air pollution and its directing effect to operation of precipitation/snow enhancement during winter over Dalian city

利用国家环境保护部大气污染指标和常规气象观测资料,结合区域空气质量模式系统(Weather Research and Forecasting-Community M ultiscale Air Quality,WRF-CM AQ)的模拟结果,对2015年12月大连市大气污染过程的气象要素和气溶胶的时空分布特征进行了分析,并对大气污染天气条件下有效开展人工增雨(雪)作业进行了初步探讨。结果表明:2015年12月大连市出现5次大气污染过程,累积污染日数为13 d,占12月总日数的41.94%,且日平均最低能见度为2.27 km。出现大气污染时,近地面温度均略有升高,大气层结稳定,因此,实施人工增雨(雪)作业时,宜选用增雨火箭和增雨飞机,从而保障催化剂可以播撒到高效核化层高度(-15℃^-10℃);同时,模拟结果表明,污染天气条件下一定量的细颗粒物在大气各种扰动下可以扩展至3.00 km以上,对具有增雨(雪)潜力的冷云实施作业时,应考虑催化剂量在常规作业剂量基础上适当减少。通过对2015年12月大连市的一次重度大气污染个例分析发现,大连市形成重污染的大气气溶胶物种主要为硝酸盐、铵盐和硫酸盐,其中硝酸盐占比最大,可以达到51.27%,说明除了相关工业源和燃煤排放,交通源排放也是大连市主要的大气污染源之一。

The temporal and spatial distribution characteristics of meteorological elements and aerosol in Dalian in December of2015when some air pollution events occurred were analyzed using the conventional meteorological observation data and air pollution indices from the Ministry of Environmental Protection of China as well as the simulation results from the regional air quality WRF-CMAQ(Weather Research and Forecasting Community Multi scale Air Quality)model.Under the air pollution weather conditions,how to carry out precipitation/snow enhancement operation was discussed as well.The results show that there are five air pollution events during December of2015in Dalian city,with a persistent time of13days,which is41.94%of the total number of days in this month.The daily mean lowest visibility is227km.When the air pollution events occur,the temperature near surface increases slightly,and the atmospheric stratification is stable.Thus,it is suitable to choose aircraft or rocket to carry out the precipitation/snow enhancement operations in order to guarantee the catalyst to be sowed to the nucleation layer with the temperature of15℃~10℃.A certain amount of fine particles can reach up to the height of more than3.00km under the air pollution weather conditions.Therefore,the amount of catalyst should be properly reduced on the basis of the normal level when operating on the cold cloud target.Based on the analysis of a serious air pollution cases occurring in Dalian in December,it reveals that nitrate,ammonium,and sulfate are the main pollutant components,and the percentage of nitrate is the highest among these components,reaching51.27%;it suggests that,except industrial sources and coal emissions,car emissions are also responsible for the pollution in Dalian city.