运用Models-3/CMAQ模式系统,模拟分析了2014年11月3~11日APEC会议期间北京市PM2.5污染的时空分布特征,并利用过程分析工具IPR研究了会期两次短时间污染过程(4日13:00~5日12:00和10日13:00~11日12:00)中各种大气物理化学过程对城区官园和郊区定陵两个代表性站点近地面PM2.5生成的贡献.结果表明,CMAQ模型合理地再现了北京市PM2.5的浓度水平和时间变化.北京地区4日和10日发生不利于污染物扩散的气象条件,导致PM2.5小时浓度出现高值(分别为188, 124μg/m3),但受减排措施和冷高压的作用,PM2.5高值维持时间较短.4日13:00~5日12:00,水平传输是官园和定陵站点PM2.5的主要贡献者,贡献率分别为49.6%和90.9%.此次污染过程北京地区受南部污染传输影响较强.10日13:00~11日12:00,官园站点PM2.5主要来自源排放在本地的积累(78.8%),定陵站点PM2.5主要来自较弱的水平传输(93.9%).此次过程体现出更加明显的局地性污染特征.两次过程中,PM2.5的主要去除途径均为垂直传输.%Models-3/CMAQ modeling system was used to simulate the spatial and temporal distribution of PM2.5 pollution over Beijing during APEC, 2014(i.e. November 3 to 11, 2014). IPR, a process analysis tool embedded in CMAQ, was employed to quantify the contributions of different atmospheric processes to the PM2.5 formation at two typical sites (i.e. Guanyuan and Dingling) during two short-time pollution processes (i.e. Nov. 4 13:00 to Nov. 5 12:00 and Nov. 10 13:00 to Nov. 11 12:00). The results showed that CMAQ reproduced the temporal variation and magnitude of PM2.5 reasonably. Adverse synoptic system occurred on Nov. 4 and Nov. 10, resulting in two peak values of PM2.5 (188μg/m3 and 124μg/m3). Elevated PM2.5 levels didn't last long because of the pollution control measures and the cold anticyclone. During Nov. 4 13:00 to Nov. 5 12:00, horizontal transport was the primary contributor to the PM2.5 at both Guanyuan and Dingling, with a contribution rate of 49.6% and 90.9%, respectively, indicating that Beijing was mainly affected by pollution transported from southern areas. During Nov. 10 13:00 to Nov. 11 12:00, PM2.5 at Guanyuan site mainly came from local emission (78.8%), while PM2.5 at Dingling site mainly came from relatively weak horizontal transport, demonstrating a local pollution characteristic. Vertical transport played a dominative role in the decrease of PM2.5 in both pollution processes.
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