黄海晚冬一次持续性海雾天气的动力热力特征

Dynamic and thermodynamic characteristics of a persistent sea fog over the Yellow Sea in late winter

利用常规资料、NCEP 1°×1°再分析资料、高分辨率可见光卫星云图资料,描述了2011年2月22—24日持续性海雾的发生范围、演变过程,分析了海雾发生前、发生时大气背景和物理量场;并利用环黄海北部的探空站、气象自动站资料对海雾发生时低层大气的温度、风、逆温特征进行了分析。结果表明:环黄海北部4个气象站中,各站出现海雾的特征不尽相同,既有以平流雾为主的、也有辐射雾为主的、还有平流雾和辐射雾共存的。对流层低层暖平流有助于保持逆温层、维持大气层结稳定;对流层低层偏南气流形成的水汽输送带和中层偏西气流水汽输送带的共同作用为大雾的形成和维持提供了水汽条件;夜晚低层辐合、高层辐散的动力分布有助于逆温层内弱的上升气流维持,对水汽凝结有利;白天低层辐散、高层辐合的动力分布有助于气流下沉,对稳定度和逆温的维持有利;负(冷)温度平流南下是大雾消散的动力热力因子。

In this paper, based on the conventional data ofNCEP1°×1 reanalysis data and high-resolution visi- ble satellite cloud images, the area of occurrence and evolution processes of persistent sea fog during February 22-24 2011 over the Yellow Sea were described. The atmospheric background and physical fields before the oc- currence of the sea fog were studied. Based on the data of sounding and automatic weather stations at the north- ern Yellow Sea rim, temperature, wind and temperature inversion at the lower atmosphere were also analyzed when the sea fog occurs. The results showed that the sea fog has different characteristics in the four weather sta- tions surrounding the northern Yellow Sea. Some are dominated by advection fog, and some by radiation fog, while others are determined by the mixture of the two. The warm advection in the lower troposphere helps to keep the temperature inversion and maintain the stability of atmospheric stratification. The water vapor formed by the airstreams conveyor belt in the lower troposphere, and the mid-level moisture conveyor belt together pro- vide sufficient water vapor conditions for the formation and maintenance of the fog. At night, the dynamical pat- tern of low-level convergence and upper-level divergence help to maintain the weak updraft within the tempera- ture inversion layer, which is conductive to the water vapor condensation. An inverted daytime pattern helps the subsidence of airflow, which helps to maintain the stability and temperature inversion. The southward advance of cold temperature advection is the dynamic and thermodynamic factor for fog dissipation.