Shahgedanova Maria, Lamakin Mikhail
Department of Geography, The University of Reading, Whiteknights, P.O. Box 227, Reading RG6 6AB, UK.
Sci Total Environ. 2005 Apr 1;341(1-3):133-48. doi: 10.1016/j.scitotenv.2004.09.018.
Temporal and spatial variability of aerosol optical depth (AOD) are examined using observations of direct solar radiation in the Eurasian Arctic for 1940-1990. AOD is estimated using empirical methods for 14 stations located between 66.2 degrees N and 80.6 degrees N, from the Kara Sea to the Chukchi Sea. While AOD exhibits a well-known springtime maximum and summertime minimum at all stations, atmospheric turbidity is higher in spring in the western (Kara-Laptev) part of the Eurasian Arctic. Between June and August, the eastern (East Siberian-Chukchi) sector experiences higher transparency than the western part. A statistically significant positive trend in AOD was observed in the Kara-Laptev sector between the late 1950s and the early 1980s predominantly in spring when pollution-derived aerosol dominates the Arctic atmosphere but not in the eastern sector. Although all stations are remote, those with positive trends are located closer to the anthropogenic sources of air pollution. By contrast, a widespread decline in AOD was observed between 1982 and 1990 in the eastern Arctic in spring but was limited to two sites in the western Arctic. These results suggest that the post-1982 decline in anthropogenic emissions in Europe and the former Soviet Union has had a limited effect on aerosol load in the Arctic. The post-1982 negative trends in AOD in summer, when marine aerosol is present in the atmosphere, were more common in the west. The relationships between AOD and atmospheric circulation are examined using a synoptic climatology approach. In spring, AOD depends primarily on the strength and direction of air flow. Thus strong westerly and northerly flows result in low AOD values in the East Siberian-Chukchi sector. By contrast, strong southerly flow associated with the passage of depressions results in high AOD in the Kara-Laptev sector and trajectory analysis points to the contribution of industrial regions of the sub-Arctic. In summer, low pressure gradient or anticyclonic conditions result in high atmospheric turbidity. The frequency of this weather type has declined significantly since the early 1980s in the Kara-Laptev sector, which partly explains the decline in summer AOD values.
利用1940 - 1990年欧亚北极地区太阳直接辐射观测数据，研究了气溶胶光学厚度（AOD）的时空变化。采用经验方法对位于北纬66.2度至80.6度之间、从喀拉海到楚科奇海的14个站点的AOD进行了估算。虽然所有站点的AOD都呈现出众所周知的春季最大值和夏季最小值，但欧亚北极西部地区（喀拉海 - 拉普捷夫海）春季的大气浑浊度更高。6月至8月期间，东部地区（东西伯利亚海 - 楚科奇海）的透明度高于西部地区。在20世纪50年代末至80年代初，喀拉海 - 拉普捷夫地区观测到AOD有显著的正趋势，主要出现在春季，此时源自污染的气溶胶在北极大气中占主导地位，但东部地区没有这种趋势。尽管所有站点都地处偏远，但呈现正趋势的站点距离人为空气污染源更近。相比之下，1982年至1990年期间，春季在北极东部地区观测到AOD普遍下降，但仅限于北极西部地区的两个站点。这些结果表明，1982年后欧洲和前苏联人为排放量的下降对北极地区的气溶胶负荷影响有限。1982年后，夏季AOD出现负趋势，此时大气中存在海洋气溶胶，这种情况在西部地区更为常见。采用天气气候学方法研究了AOD与大气环流之间的关系。春季，AOD主要取决于气流的强度和方向。因此，强劲的西风和北风气流导致东西伯利亚海 - 楚科奇地区的AOD值较低。相比之下，与低压槽过境相关的强劲南风气流导致喀拉海 - 拉普捷夫地区的AOD较高，轨迹分析表明亚北极工业区对此有贡献。夏季，低压梯度或反气旋条件导致大气浑浊度较高。自20世纪80年代初以来，喀拉海 - 拉普捷夫地区这种天气类型的频率显著下降，这部分解释了夏季AOD值的下降。
