沙尘气溶胶的跨亚欧大陆传输对东亚地区大气环境的影响

Impact of trans-eurasian dust aerosol transport on atmospheric environment in East Asian Region

基于全球大气环流模式CAM3.1对2002—2003年模拟的全球沙尘气溶胶分布及其变化的评估,通过去除东亚沙漠(局地源)的敏感性模拟试验来分析北非、阿拉伯和中亚地区沙漠区(外部源)的沙尘气溶胶跨亚欧大陆传输对东亚地区大气沙尘气溶胶的贡献.结果表明,受到大气沙尘气溶胶的跨亚欧大陆传输的影响,东亚以外沙尘源对青藏高原大气贡献率最大,对我国北方干旱半干旱地区大气贡献率最小,对中国南方地区和日韩及邻近的西北太平洋地区大气贡献率基本相当.东亚地区秋(冬)季大气受到东亚以外沙尘源的影响最弱(强).我国北方干旱半干旱地区近地层大气沙尘气溶胶的外源贡献率秋季最小(约5%),冬季最大(约30%).青藏高原冬季60%~80%的近地面大气沙尘气溶胶来自东亚以外的沙漠区,而在秋季则只有约20%~60%.外源对东亚大气沙尘气溶胶柱浓度和对近地面大气沙尘气溶胶的影响具有基本一致的季节特征,但对柱浓度的贡献率一般偏大10%~40%.沙尘气溶胶跨亚欧大陆传输对东亚地区的影响主要集中在2~6 km的自由对流层.随对流层高度的增加东亚各地区外源贡献率均增加.青藏高原地区以年平均对流层沙尘气溶胶外源贡献率62%~81%成为东亚地区最大的影响区域.

Based on the evaluation of global soil dust aerosols simulated by the global climate model CAM3.1 during 2 years( 2002—2003),a sensitivity experiment with removal of East Asian deserts was conducted to explore the contribution from external dust aerosol sources over the African,Arabian and central Asian deserts to the atmospheric environment over East Asia through trans-Eurasian dust aerosol transport. Under the impact of Trans-Eurasian transport,the external dust emission sources contributed the most significantly to the dust aerosols in the Tibetan Plateau,the least to the arid and semiarid regions in northern China,and comparably to southern China and Korean Peninsula,Japan and the adjacent northwest Pacific region. The contribution rates from external dust aerosols presented a distinct seasonal variation in the East Asian region,the largest in winter about 60% ~ 80% over the Tibetan Plateau and 30% over northern China while the smallest in autumn about 20% ~ 60% over the Tibetan Plateau and only 5% in northern China.The seasonal patterns of the external dust contribution to tropospheric loading and surface concentrations over East Asian region were generally consistent,and the contribution rate to dust loading was 10% ~ 40% higher than that to surface dust concentrations. The influences of external dust aerosol werevertically concentrated at 2 ~ 6 km in the free troposphere with larger contribution rate at the higher elevation. Tibetan Plateau was the region with the largest impact of external dust aerosols,with 62% ~ 81% contributed by external dust aerosols on the annual average.