The challenge of improving visibility in Beijing
The challenge of improving visibility in Beijing
复制标题
提高北京知名度的挑战
DOI：
10.5194/acp-10-7821-2010
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发表时间：
2010-08
影响因子：
6.3
通讯作者：
Xue, H. W.
中科院分区：
文献类型：
--
作者：
Zhang, Q. H.;Zhang, Q. H.;Zhang, J. P.;Zhang, J. P.;Xue, H. W.;Xue, H. W.
抽象的。“蓝天计划”于1998年提出，旨在调查应减少多少排放量以增加北京的蓝天频率，北京曾举办过2008年夏季奥运会。利用北京首都国际机场1999 - 2007年逐时能见度观测资料，分析了北京地区能见度的时间变化及其与气象条件和悬浮颗粒物的关系。研究发现，1999 - 2007年北京市能见度小于10 km（等于或大于20 km）的不良（良好）时数占总时数的47.8%（24.2%）。由于相对湿度（RH）高，夏季是一年中平均能见度最低的季节。虽然PM10指数呈下降趋势（Chan和Yao，2008），但相对湿度的增加导致1999 - 2007年夏季北京首都国际机场能见度呈下降趋势。为了确保2008年奥运会的蓝天（“良好”能见度），每日平均PM10指数应从81降至44。这就要求不仅要限制汽车排放，还要限制其他排放。2008年奥运会期间PM10平均指数降至53后，蓝天小时率显著增加，但2009年8月8日至24日期间能见度恢复到1999年至2007年的平均水平。2008年8月，相对湿度（气溶胶）对能见度改善的贡献率为24%（76%）。
Abstract. The "Blue Sky Project" was proposed in 1998 to investigate by how much emissions should be reduced to increase blue sky frequency in Beijing, which hosted the Summer Olympics in 2008. This paper focuses on the temporal variation of visibility and its dependence on meteorological conditions and suspended particles at Beijing using the hourly observed visibility data at Beijing Capital International Airport (BCIA) from 1999 to 2007. It has been found that about 47.8% (24.2%) of the hours in Beijing are "bad" ("good") hours with visibility below 10 km (equal or higher than 20 km) between 1999 and 2007. Due to the high Relative Humidity (RH), summer is the season with the lowest mean visibility in a year. Although PM10 index was reported in a decreasing trend (Chan and Yao, 2008), the increase of RH has resulted in a decreasing trend of visibility over BCIA in the summer from 1999 to 2007. To ensure blue sky ("good" visibility) for Olympics 2008, daily mean PM10 index should have been reduced from 81 to 44. This requires that not only vehicle emissions, but also other emissions should be limited. Observations verify that blue-sky-hour rate increased significantly after mean PM10 index was reduced to 53 during Olympics 2008, however, the visibility of 2009 returned to the mean level from 1999 to 2007 during the period 8−24 August. RH (aerosol) contribute 24% (76%) of the improvement of visibility during August 2008.
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