Asian chemical outflow to the Pacific in late spring observed during the PEACE-B aircraft mission
Asian chemical outflow to the Pacific in late spring observed during the PEACE-B aircraft mission
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DOI：
10.1029/2004jd004976
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发表时间：
2004-12
影响因子：
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通讯作者：
N. Oshima;M. Koike;H. Nakamura;Y. Kondo;N. Takegawa;Y. Miyazaki;D. Blake;T. Shirai;K. Kita;S. Kawakami;T. Ogawa
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文献类型：
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作者：
N. Oshima;M. Koike;H. Nakamura;Y. Kondo;N. Takegawa;Y. Miyazaki;D. Blake;T. Shirai;K. Kita;S. Kawakami;T. Ogawa
[1]2002年4月至5月，在西太平洋上空进行了亚洲大陆排放物太平洋探测B阶段（PEACE-B）飞机使命。在几次飞行中，在5至10公里的高度观察到CO的大量增加，按体积计算超过十亿分之200（ppbv）。在本文中，我们描述了东亚的垂直传输机制，负责这些增强，使用欧洲中期天气预报中心（ECMWF）的气象数据和红外云数据获得的地球静止气象卫星（GMS）-5。对一次最高CO事件的个例分析表明，这可能是由于中国中部（30°N长江附近）形成的准静止锋带引起的深积云对流沿着污染物垂直输送所致。在PEACE-B期间的平均气象场中，温暖、潮湿的低层南风汇集到锋区，维持锋面两侧的温度和湿度差异。沿锋面沿着，平均垂直运动明显向上，高空副热带急流能有效地将上升气流输送到西太平洋。在这项研究中，使用ECMWF和GMS数据定义了识别深对流的标准。结果表明，副热带急流下方的对流活动对中国中部地区上升气流的产生起着重要作用。对流输送主要是由有限的几次事件造成的，每次事件都伴随着弱气旋扰动的发展。PEACE-B期间在飞机上高度4至13公里处采样的空气包的后轨迹显示，在来自800百帕或以下的空气包中，69%可能经历了对流抬升。除了对流，倾斜的等熵线经常观察到沿着准定常射流轴产生持续缓慢的准绝热上升的空气在远东地区，这是偶尔加强与经典的暖传送带（WCB）气流的迁移气旋扰动的通道。因此，PEACE-B期间的气象条件有利于中国中部地区受人为排放影响的边界层空气抬升。这些结果是一致的哈龙1211（CF2 ClBr），一个很好的中国人为排放的示踪剂，在空气中观察到的可能在锋区隆起的包裹相对较高的水平。
[1] The Pacific Exploration of Asian Continental Emission phase B (PEACE-B) aircraft mission was conducted over the western Pacific during April–May 2002. During several flights, large enhancements of CO greater than 200 parts per billion by volume (ppbv) were observed at altitudes between 5 and 10 km. In this paper, we describe vertical transport mechanisms over east Asia that were responsible for these enhancements, using the European Centre for Medium-Range Weather Forecasts (ECMWF) meteorological data and infrared cloud data obtained by the Geostationary Meteorological Satellite (GMS)-5. A case study for the highest CO event shows that it was likely due to vertical transport of pollutants caused by deep cumulus convection along a quasi-stationary frontal zone, which was formed over central China (around the Yangtze River at 30°N). In the mean meteorological field during the PEACE-B period, the warm, moist low-level southerlies converged into the frontal zone, sustaining cross-frontal temperature and moisture contrasts. Along the frontal zone, the mean vertical motion was distinctively upward, and a subtropical jet aloft was found to transport uplifted air parcels efficiently into the western Pacific. In this study, criteria to identify deep convection are defined using both the ECMWF and GMS data. The results show that convective activity, which was generally high below the subtropical jet, played an important role in producing updrafts over central China. The convective transport resulted mainly from a limited number of episodes, each of which followed the development of a weak cyclonic disturbance. Back trajectories of air parcels sampled at altitudes between 4 and 13 km on board the aircraft during PEACE-B show that among the air parcels originating from the 800-hPa level or below, 69% were likely to have undergone convective uplifting. In addition to convection, sloping isentropes often observed along the quasi-stationary jet axis yielded persistent slow quasi-adiabatic uplifting of air over the Far East, which was occasionally intensified with a classical warm conveyor belt (WCB) airstream on the passage of migratory cyclonic disturbances. Meteorological conditions during PEACE-B were thus favorable for the uplifting of boundary layer air influenced by anthropogenic emissions over central China. These results are consistent with the relatively high levels of Halon 1211 (CF2ClBr), a good tracer of Chinese anthropogenic emissions, observed in the air parcels that were likely uplifted in the frontal zone.