浙江省大气扩散能力的时空分布特征

利用以美国环保部推荐的经典高斯扩散模型为基础建立的大气扩散能力定量评估方法，研究浙江省大气扩散能力分布及年际变化特征。研究结果表明，浙江省大气扩散能力呈北部较南部强、沿海较内陆强的分布特点，不同设区市大气扩散指数从大到小的顺序为舟山(3.25)>台州(2.69)>嘉兴(2.22)>宁波(2.19)>衢州(1.75)>金华(1.70)>绍兴(1.67)>湖州(1.46)>杭州(1.34)>温州(1.27)>丽水(0.59)。不同时间尺度大气扩散能力特征为:7月大气扩散指数最大，达到4.19，2月最小，为1.51；夏季大气扩散指数最大，为3.37，秋季次之，为2.73，春季第三，为2.44，冬季最小，为1.94；1980—2014年年均大气扩散指数呈明显的下降趋势，下降了1.40，下降幅度达到58.33 %，而且2000年之后的下降速率较之前大。不同设区市大气扩散指数年际变化特征存在较大差异，表现最明显的有:温州地区大气扩散指数下降幅度最大，舟山地区大气扩散指数虽然一直较其它地区大，但近几年下降幅度比较大；丽水地区大气扩散指数一直最小，但其降幅也最小。 

THE SPATIOTEMPORAL DISTRIBUTION OF ATMOSPHERIC DIFFUSION CAPACITY IN ZHEJIANG PROVINCE

Based on the evaluation method of atmospheric diffusion capacity induced by the classical Gauss diffusion model, the characteristics of the spatiotemporal distribution of atmospheric diffusion in recent decades are studied in Zhejiang. The results showed that the distribution characteristics of atmospheric diffusion capacity are stronger in the north and the coast than in the south and inland area in Zhejiang. In different prefectures, the order of atmospheric diffusion indexes is Zhoushan(3.25) > Taizhou(2.69) > Jiaxing(2.22) > Ningbo(2.19) > Quzhou(1.75)>Jinhua(1.70) > Shaoxing(1.67) > Huzhou(1.46) > Hangzhou(1.34) > Wenzhou(1.27) > Lishui(0.59). The atmospheric diffusion index is the largest in July, which is 4.19, and the minimum in February, which is 1.51. The seasonal sequence of atmospheric diffusion indexes is summer(3.37)>autumn(2.73)>spring(2.44)>winter (1.94). The annual average atmospheric diffusion index shows an obvious decreasing trend from 1980 to 2014 and the decreasing amplitude is about 1.40, reaching 58.33%. Furthermore, the rate of decline after 2000 is slightly larger than before. The inter-annual variations of atmospheric diffusion indexes in different prefectures are different and the most special variations happened in Wenzhou, Zhoushan and Lishui areas. First, the biggest decline in the past decades is in Wenzhou prefecture; second, although it shows higher atmospheric diffusion indexes in Zhoushan prefecture than in other areas, the decline amplitude is large in recent years. Lastly, the minimum decline happened in Lishui prefecture although it had the lowest atmospheric diffusion index compared with other prefectures.