上海地区AQI变化特征及与气象因素的相关性

基于上海地区2012—2016年逐日PM_2.5、PM₁₀、CO、O₃、SO₂、NO₂的分指数（individual air quality index，IAQI）数据以及同期气象要素（风速、降水量、气温、相对湿度、总云量、低云量）、逆温数据和高空大气环流数据，分析了上海地区空气质量指数的时间变化特征和气候要素对空气质量的影响，并选取PM_2.5和O₃污染天气过程及其邻近的非污染天气过程，对比分析高空大气环流形势的差异。结果表明：上海地区出现PM_2.5、PM₁₀和NO₂污染天气在冬季最多，分别为31.4 d、10.0 d和14.8 d，而O₃污染天气在夏季最多（18.8 d）。风速和低云量是影响PM_2.5污染的重要气象因素，最大相关系数分别为-0.313和-0.261，O₃污染则与气温和日照时数密切相关，最大相关系数分别为0.449和0.363，PM_2.5、O₃污染的发生也与前一日以及当日出现逆等温天气存在较好的相关性。在PM_2.5污染天气过程，上海位于槽后高压前部，850 hPa有较强西北风，而非PM_2.5污染天气过程中上海位于高压后部，低层850 hPa为东南风。在O₃污染天气和非污染天气过程，中国东部长波射出辐射（Outgoing Longwave Radiation，OLR）分别为正、负距平，副热带高压控制下上海晴热少云，易引起O₃污染，反之上海上空云系多，不容易出现污染。

Characteristics of air quality index and its correlation with meteorological parameters in Shanghai

Based on the daily individual air quality index (IAQI) of PM_2.5,PM₁₀,CO,O₃,SO₂,and NO₂,observations of meteorological parameters (including wind speed,precipitation,temperature,relative humidity,total cloud cover,and low cloud cover),temperature inversion and upper-level atmospheric circulation data from 2012 to 2016,we analyzed the temporal variation of air quality index and the impact of climatic elements on air quality in Shanghai.We also compared the differences in atmospheric circulation during PM_2.5 and O₃ pollution events and clean days nearby.The results showed that the PM_2.5,PM₁₀,and NO₂ pollution events occur frequently in winter,with day numbers of 31.4 d,10.0 d and 14.8 d,respectively,while O₃ pollution events occur most frequently in summer (18.8 d).Wind speed and low cloud cover greatly affect PM_2.5 pollution,with the correlation coefficient of -0.313 and -0.261,respectively.O₃ pollution is closely related to air temperature and sunshine duration,with the correlation coefficient of 0.449 and 0.363,respectively.The formation of PM_2.5 and O₃ pollution also have a high correlation with a temperature inversion on the day and the former day.During PM_2.5 pollution events,Shanghai is located ahead of a high behind a trough,accompanied by strong northwesterly winds at 850 hPa,while for clean days,Shanghai is behind a high and the southeasterly flows are dominated at 850 hPa.For O₃ pollution events and clean days,the anomaly of outgoing longwave radiation (OLR) over eastern China is positive and negative,respectively.O₃ pollution is easy to occur under a clear sky and low cloud cover conditions due to the subtropical high,and it hardly occurs in the presence of high cloud cover in Shanghai.