不同气流路径的春季黄海海雾天气与大气-海洋特征

春季（四至五月）是黄海海雾的多发季节，也是亚洲季风的转换季节。 本文对发生在1960-2006年春季的黄海海雾，及其雾气相关的天气特征和大气-海洋条件进行了综合分析。海雾根据I_COADS海面观测数据和同期NCEP/NCAR再分析资料风场的气流后向轨迹聚类分析，可进行气流路径分类。在气流路径分析的基础上，对春季黄海海雾的大尺度低层环流型及其相关的地表散度、湿度垂直分布、水汽水平输送及大气-海表温度差异进行了分析。主要结论总结如下：（1）导致春季黄海海雾形成的气流主要可分为四条路径。气流分别来自黄海的西北、东、东南和西南侧。（2）春季黄海海雾的发生有两种典型的天气型：黄海高压型（HSH）、气旋和反气旋耦合型（CAC）。两种天气型在四月份的出现比例大致相同；但在五月份HSH型的出现比例下降到三分之一左右，而CAC型上升到三分之二左右。（3）HSH和CAC两种天气型的共同特征是黄海位于地面散度中心。 （4）对于HSH型海雾，水汽主要来自局部蒸发，低层大气之上存在明显的干层；对于CAC型雾，水汽主要来自黄海以外，低层大气具有深厚的高湿度层。（5）由于天气型及其湿度垂直分布和水汽水平输送的差异，海雾可分为两类。多数的CAC型海雾为“暖”海雾，而HSH型海雾中的“暖”和“冷”海雾的比例几乎相同。

The spring Yellow Sea fog: synoptic and air-sea characteristics associated with different airflow paths

The fog occurs frequently over the Yellow Sea in spring (April–May), a climatical period of Asian monsoon transition. A comprehensive survey of the characteristic weather pattern and the air-sea condition is provided associated with the fog for the period of 1960–2006. The sea fog is categorized by airflow pathways of backward trajectory cluster analysis with the surface observations derived from international comprehensive oceanatmosphere dataset (I_COADS) I_COADS datasets and contemporaneous wind fields from the National Centers for Environmental Prediction (NCEP)/National Center for Atmospheric Research (NCAR) reanalysis. On the basis of the airflow paths, the large-scale lower-tropospheric circulation patterns and the associated surface divergence, the distribution of a vertical humidity, the horizontal water vapor transportation and the air-sea temperature difference are investigated and the major findings are summarized as follows. (1) Four primary clusters of the airflow paths that lead to spring sea fog formation are identified. They are originated from the northwest, east, southeast and southwest of the Yellow Sea, respectively. (2) Springtime Yellow Sea fog occurs under two typical weather patterns: the Yellow Sea high (YSH) and cyclone and anticyclone couplet (CAC). Each pattern appears by about equal chance in April but the YSH occurrence drops to around one third and the CAC rises to around two third of chance in May. (3) The common feature in the two types of synoptic conditions is that surface divergence center is located over the Yellow Sea. (4) For the YSH type of fog, water vapor comes mainly from local evaporation with a well-defined dry layer present in the lower atmosphere; for the CAC type of fog, however, water vapor comes mainly from areas outside the Yellow Sea with a thick surface layer of high humidity. (5) With the differences in weather patterns and its associated vertical distribution of the humidity and the transportation of water vapor, there are two types of sea fogs. Most fogs of the CAC types are “warm” fog, while fogs of YSH type have nearly equal chance to be “warm” and “cold” fog.