东亚太平洋地区近地面臭氧的季节和年际变化特征及其与东亚季风的关系

利用东亚清洁背景站近地面臭氧观测资料，结合风场和降水资料，分析东亚各地区臭氧的多年季节变化特征，并探讨东亚太平洋地区臭氧的季节和年际变化与季风的关系以及影响近地层臭氧的主要因子。结果表明：东亚大部分地区与北半球背景站观测一致，近地层臭氧季节变化表现为春季最高、夏季最低的特征；但在东亚中纬度33～43°N，臭氧表现为夏季最高，而在东亚20°N以南地区臭氧则表现为冬末、春初最高。东亚太平洋沿岸近地面臭氧的季节变化主要受东亚冬、夏季风环流的季节变化控制。该地区不同纬度上春季峰值出现时间的差异与亚洲大陆春季不同时期污染物输送路径的差异有关。对东亚太平洋沿岸对流层顶附近位势涡度、高空急流和垂直环流季节变化的分析表明，冬春季可能是平流层向对流层输送的最强期，对近地面臭氧贡献最大。初夏至秋季（5-11月），平流层向对流层输送较弱，对近地面臭氧贡献较小。东亚太平洋地区夏季风爆发的时间和强度以及季风环流型的年际差异是导致该地区春、夏季臭氧年际变化的主要原因；而季风降水和云带位置以及平流层一对流层交换是造成臭氧年际变化的其他原因。

Seasonal and interannual variation features of surface ozone over East Asia-Pacific region and its relation with East Asian monsoon

By using the monthly surface ozone data collected at remote sites over East Asia（EA） and related wind field and precipitation data, this paper studies the ozone seasonal cycle, interannual varia- tion characteristics and their relations to EA monsoon, and the main factors influencing the surface o- zone. The results show that the spring maximum and summer minimum of surface ozone occurs widely across mid-latitudes in the North Hemisphere at remote sites,including most parts of EA. However, the surface ozone has a summer maximum in the region of 33--43~N over EA, and a later winter/early spring maximum in south of 20~N over EA. These ozone seasonal cycle features were mainly controlled by the seasonal transitions of East Asia winter/summer monsoon circulations. The latitudinal differences of appearing time of surface ozone peaks in spring over EA Pacific Rim regions are closely related to the differences of pollutants transport path and strength from Asian continental. The analysis of seasonal variations of potential vorticity, upper air jet stream around tropopause, and the variation of vertical circulations shows that the winter and spring are the strongest periods of air mass transport from strato- sphere to troposphere. However, the transport from stratosphere to troposphere is weakest from May to November and has lower impact on surface ozone. The interannual variations of EA summer monsoon onset（time and strength） and patterns of circulation are the main reasons of surface ozone interannual variations in spring and summer over EA Pacific Rim regions. The other factors for surface ozone varia- tion could be attributed to monsoon precipitations, cloud effects on photochemistry and the stratosphere- troposphere transport.