我国东部沿海一次局地海雾抬升成云过程分析

Analysis of the Process of A Local Sea Fog Lifted Into Low Cloud in Eastern China

利用洪家站L波段雷达探空资料、高分辨率海气耦合模式再分析资料、静止气象卫星云图和地面观测资料,分析了一次黄东海海雾抬升为低云,使海雾消散的过程。发现近海面偏南风速突然增强,海洋大气边界层(MABL)中机械剪切加强,湍流混合层向上发展,是导致海雾抬升转化为低云的主要原因。近海面风速突然增加与高空急流北抬、平均层槽脊振幅加大、槽前正涡度平流输入诱使地面低压系统发展、地面气压梯度力增大有关。近海面气温升高对海雾消散也有作用,气温升高的原因是暖平流、绝热下沉和海气界面热通量的综合效应。其中,东海海洋锋(STF)冷区的下沉气流可能对边界层内的绝热下沉增温和低云的形成高度有重要的影响。该研究为海雾消散预报提供了新的思路。

In this paper, the Hongjia single-station L-band radar sounding data, high-resolution coupled ocean-atmosphere model reanalysis data, geostationary meteorological satellite imageries and ground observations are used to analyze a local sea fog dissipated process due to the sea fog uplift into the low clouds in the East China Sea. The analysis found that near sea surface wind speed increased sud- denly, the mechanical shear strengthening in the marine atmospheric boundary layer （MABL） and up- ward development of the turbulent mixing layer, resulting in the uplift of sea fog conversion for low clouds. The sudden increase in near sea surface wind speed is related to the high-altitude jet stream northward, trough and ridge amplitude in average layer intensify, the input of positive vorticity advection in front of trough induce the ground low-pressure system development, surface pressure gradient force increases. Near sea surface temperature rise also contributed to the dissipation of sea fog. Rising temperature caused by the combined effect of the warm advection, adiabatic sinking and the air-sea interface heat flux. The downdraft in the cold water side of oceanic front may have a significant influence in warming of adiabatic sinking in MABL and the formation of the height of low cloud. The study provides a new approach to sea fog dissipation forecast.