两种典型大气扩散指数在新疆的分布特征及其适用性对比

Comparison of the distribution and applicability of two typical atmospheric diffusion indices in Xinjiang

为定量评估气象条件对空气污染的作用,利用2010—2020年新疆14个气象探空站及地面气象观测站资料计算大气自净能力指数和静稳指数,对比分析两者在新疆的时空分布特征及其适用性,结果表明:新疆的大气自净能力指数与静稳指数呈反位相分布,两者具有较好的相关性,相关系数达-0.89。大气自净能力指数在夏季最大[9.4 t·(d·km^(2))^(-1)],冬季最小[0.9 t·(d·km^(2))^(-1)],南疆[6.2 t·(d·km^(2))^(-1)]普遍大于北疆[6.0 t·(d·km^(2))^(-1)];静稳指数在冬季最大(5.1),夏季最小(0.7),南疆(1.6)普遍小于北疆(3.8),即南疆的大气扩散条件较北疆好,北疆较南疆更容易形成静稳天气。通过分析2015—2020年大气环境监测站逐日污染数据发现,大气自净能力指数和静稳指数在天山北坡对PM2.5和PM10均有较好的指示意义;在阿勒泰两个指数对PM2.5有较好的指示意义;在阿克苏静稳指数与PM2.5的相关关系通过了显著性检验;在和田自净能力指数与PM10通过了显著性检验。对于首府乌鲁木齐,当污染物排放严重时,若大气自净能力指数在0~20 t·(d·km^(2))^(-1),则易出现重污染天气;静稳指数范围参考意义不大。

To quantitatively evaluate the effect of meteorological conditions on air pollution,data from 14 meteorological sounding stations and surface observation stations in Xinjiang were used to analyze the spatial and temporal distribution characteristics of atmospheric self-purification capacity index(ASI)and air stagnation index(ASITS)from 2010 to 2020.Results showed a negative correlation between ASI and ASITS.ASI was the largest in summer and the smallest in winter.It was generally greater in southern Xinjiang than in northern Xinjiang,whereas ASITS showed the opposite trend.This implied that the atmospheric diffusion conditions were better in southern Xinjiang than in northern Xinjiang,and a static and stable atmospheric circulation more easily formed in northern Xinjiang than in southern Xinjiang.The daily pollution data of air environment monitoring stations from 2015 to 2020 were used to determine the correlation between the air quality of Xinjiang in different seasons and the air quality of five heavily polluted stations and the two indexes.The two indexes highly correlated with the air pollution data of Urumqi station,and the static stability index was better,which can well indicate the degree of air pollution.However,no good correlation was found between the two indexes and the air pollution data of four stations in the southern Xinjiang basin.In the heavy pollution case in the spring of 2018,the PM10 concentration span was very large,so the two indexes showed a high dispersion on the scatter diagram,which is not applicable.In particular,in Hotan and Aksu,the two indexes showed a certain correlation with the pollutant concentration,and ASITS performed better.In Kashgar,ASI showed no correlation with air quality,and ASITS showed a weak correlation;the two indexes showed no correlation with the air quality of Korla,implying poor applicability.Further study on the distribution of indexes under different pollution levels in the capital city of Urumqi showed that the early warning indicators can be preliminarily condensed as follows:When pollutant emission is serious,and if ASI is distributed at 0-20 t·(d·km^(2))−1,it is susceptible to heavy weather pollution,and the range of ASITS is of little significance.