摘要
西北太平洋是全球海雾最多的海域,但由于观测资料匮乏,对开阔大洋上海雾形成机理的个例研究很少。2019年9月12—14日,中国北极科考船“向阳红01号”在亲潮延伸体水域捕捉到一次海雾事件。主要利用船载观测数据,分析了海雾形成的物理过程。结果表明,这是一次温带气旋的暖锋和局地海洋锋(海面温度锋)共同影响下的海雾过程。伴随暖锋的偏南气流将暖湿空气向北输送,在亲潮延伸体区,海面空气增湿效应大于增温效应,导致相对湿度不断增加接近饱和。北上暖空气遇到较冷水域上空的冷空气团,向上爬升形成大范围锋面逆温;局地海洋锋强迫出大气边界层内的次级环流,其下沉支使该锋面逆温层底的高度进一步降低,有利于雾滴局限在近海面成雾,雾区出现于暖锋锋面过后局地海洋锋的冷水侧。这项研究明确了海雾形成过程中作为背景环流的大气暖锋与作为局地强迫项的海洋锋的贡献,可为海雾预报提供新的理论支撑。
The western North Pacific is the foggiest oceanic area in the world,yet the synoptic processes of sea-fog formation over open oceans remain unclear due to the lack of observations so far.A Chinese arctic research vessel,Xiang Yang Hong 01,captured a fog event in the cold Oyashio Extension(OE)area from 12 to 14 September 2019.The formation and maintenance mechanism of the fog is investigated based on the in situ observations.The results show the fog is influenced both by a synoptic-scale warm front in an extratropical cyclone and a local sea surface temperature(SST)front.The warm moist air is transported from south to north along with the warm front,which results in the near surface air becoming warmer and wetter in the OE area.The fact that the moistening effect is greater than the heating one leads to the increase of relative humidity approaching saturation.The northward warmer air climbs upward when it meets the colder air mass over the OE waters,thus forming a large-scale frontal inversion.The forcing of the local SST front brings about a secondary circulation in the marine atmospheric boundary layer and the bottom of the inversion drops under the effect of a sinking branch from the circulation.The lowered inversion is conducive to the formation of fog droplets,which,once formed,are confined near the sea surface.The fog layer is formed in the warm moist air on the cold flank of the SST front.The contributions of the background atmospheric warm front and the local forced SST front to the sea-fog formation are clarified,which can provide a theoretical support for the forecast of sea fog.
作者
张苏平
张欣
时晓曚
ZHANG Suping;ZHANG Xin;SHI Xiaomeng(College of Oceanic and Atmospheric Sciences, Ocean University of China, Qingdao 266100, China;Qingdao Meteorological Observatory, Qingdao 266003, China)
出处
《海洋气象学报》
2022年第1期1-11,共11页
Journal of Marine Meteorology
基金
国家重点研发计划项目(2019YFC1510102)
国家自然科学基金项目(41975024)
山东省气象局科研项目(SDYBY2018-06,2017sdqxm11)。
关键词
海雾
观测
暖锋
海洋锋
西北太平洋
sea fog
observation
warm front
SST front
western North Pacific
