• 关键词：静稳天气指数(SWI)  PM_2.5  重度污染  空气质量预报  减排评估  杭州

• 基金项目：中国气象局预报员专项项目（No.CMAYBY2020-053）；浙江省气象科技计划项目（No.2020ZD13，2017ZD11，2019YB01）

• 陈懿妮
• 浙江省气象台, 杭州 310052

• 罗玲
• 浙江省气象台, 杭州 310052

• 马昊
• 浙江省气象台, 杭州 310052

• 贾燕
• 浙江省气象台, 杭州 310052

• 赵军平
• 浙江省气象台, 杭州 310052

• 徐铖
• 浙江省气象台, 杭州 310052

• 娄小芬
• 浙江省气象台, 杭州 310052

• 于燕
• 浙江省气象科学研究所, 杭州 310008

• 摘要：采用杭州市近7年的气象与环保监测资料，综合考虑2 m相对湿度、10 m水平风速、日均海平面气压、24 h变压、24 h变温、低层逆温等气象因子，通过历史样本统计划分阈值范围再权重求和的方法，构建了静稳天气指数（SWI）.经过实况回算检验，分析所建指数与污染天气的对应关系，并应用到重污染天气成因分析、空气质量预报和污染减排评估等方面.结果表明：①SWI可以综合反映大气静稳程度，与PM_2.5浓度有较好对应关系，SWI越大越容易出现污染天气，SWI大值最易出现在冬季，其次为秋季和春季，夏季主要污染物往往是臭氧，不易发生中度以上的污染天气.②SWI可用于判断杭州秋冬季重度及以上污染天气的成因，平均而言SWI<6.7时不易出现重度及以上污染；若SWI<6.7时仍出现重污染天气，可判断主导风向上游的外来污染物输入是引起重污染的主要原因，根据前期SWI的相对大小可判断有无叠加前期本地污染物积累；若SWI持续大于6.7且出现重度及以上污染天气，可判断由大气静稳而产生的本地污染物堆积是主要成因.③依据预报数据计算的SWI对空气质量分级预报有较好的参考价值，在短期和中期预报时效内均有表现力.④将SWI应用到G20会议期间污染减排效果评估中发现，在气象条件静稳程度相当时，减排措施有效降低了污染程度.

• Abstract：Based on the meteorological and environmental monitoring data of Hangzhou in the past seven years, meteorological factors including 2-meter relative humidity, 10 meter horizontal wind speed, daily mean sea level pressure, 24-hour variable pressure, 24-hour variable temperature and low-level inversion, are considered in this study. The stable weather index (SWI) is constructed by the method of weighting summation according to the historical threshold range of sample statistics. Through the backward calculation, the corresponding relationship between the SWI and pollution weather is analyzed, and it is further applied to investigate the reason of heavy pollution weather, for the air quality prediction and pollution reduction assessment. The results show that: ①SWI can comprehensively reflect the degree of atmospheric stability, and correlates well with PM_2.5 concentration. Generally, larger SWI will cause higher frequency of polluted weather. The occurrence of high SWI is most frequent in winter, followed by autumn and spring. The main pollutant in summer is often ozone, which is not likely to be related to SWI. ②SWI can be used to estimate the severity of air pollution in autumn and winter in Hangzhou. Overall,it shows challenge to cause severe air pollution when SWI is less than 6.7. If heavy pollution still occurs when SWI is less than 6.7, it indicates that the input of external pollutants in the upstream of dominant wind direction is the main cause of heavy pollution. According to the relative value of the previous SWI, it can be judged whether there is accumulation of local pollutants in the early stage of pollution development. If SWI is continuously greater than 6.7 and serious pollution weather occurred, the accumulation of local pollutants tended to be caused by the static stability of atmosphere. ③SWI calculated according to the forecast data can well predict the classification of air quality, which performs well for the short-term and medium-term forecast. ④SWI can be applied to assess the pollution reduction effect during the G20 conference. At the same level of static stability degree, the manures of emission reduction had effectively reduced the pollution degree.

• Key words：stable weather index  PM_2.5  severe pollution  air quality forecast  reduction assessment  Hangzhou

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