黄海近海至岸滨大气边界层垂直结构季节变化与海雾入侵

Sea fog is an important weather phenomenon in the marine atmospheric boundary layer （MABL）. The invasion of sea fog influences heavily the coastal social and economic activities and ecological environment. This project focuses on the spatial variations in the MABL vertical stratification from open waters to near seashore over the Yellow Sea, and the relations between the MABL variations and sea fog invasion in different seasons. We will carry out the ocean-atmosphere joint observations and the relevant theoretical research. Based on shipboard GPS soundings, satellite remote sensing data, reanalysis data and numerical models, the spatial variations in the features of the MABL vertical structures influenced by different prevailing winds will be found and the corresponding mechanisms will be explored. We will quantitatively investigate the contributions to the MABL variations in terms of sensible, latent heat flux, thermal contrast between sea and land, long-wave radiation and entrainment at tops of fog/marine stratus, etc. under different prevailing winds with different temperature, humidity and dynamic properties by climatology diagnosis and quantitative elaborate analysis. On this basis, we will construct a regional marine climatological framework, in which different large-scale background atmospheric circulations modify the MABL structure and the local vertical cells in coastal boundary layer, and thus leading to the variations in the degree and times of the sea fog intrusion. This project will enrich the mechanisms of the variations in the MABL over marginal seas in monsoon region, lay theoretical foundation for the forecast of sea fog intrusion, and provide important references for the improvement of atmospheric boundary layer parameterization schemes in the models.

海雾是海洋大气边界层（MABL）中重要的天气现象，海雾入侵岸滨对社会经济活动造成严重影响。本项目针对不同季节黄海MABL垂直结构由近海至近岸的空间变化特征及其与海雾入侵程度季节性差异的关系，开展海洋-大气联合加密观测与有关理论研究。依据船载探空数据，结合卫星遥感资料和数值模式，通过气候学诊断与天气尺度定量化分析相结合的方法，发现不同季节盛行风下，黄海近海MABL垂直结构不同的空间变化特征，揭示其变化机理；阐明因盛行风温湿性质和动力学性质的不同，海气界面潜热感热通量、海陆热性质差异及海雾/层云顶辐射和卷夹等在MABL垂直结构变化过程中的不同贡献。在此基础上，建立不同大尺度背景环流通过调控MABL温湿层结和近岸边界层内垂直环流，进而影响海雾入侵程度的区域海洋气候学框架。该研究将丰富大陆边缘海MABL变化的机理，为预报海雾入侵奠定理论基础，同时为大气模式边界层参数化方案的改进提供参考依据。

本项目依据船载探空数据，结合卫星遥感资料和数值模式，通过气候学诊断与天气尺度定量化分析相结合的方法，在对不同季节黄海海雾个例分析中，发现了黄海近海MABL垂直结构不同的空间变化特征：春季黄海海洋大气边界层（MABL）高度较低，边界层顶伴有强逆温层和明显干层，而夏季黄海MABL高度较高。不同背景气流下，在SST明显变暖的区域，“风速—热通量—静力不稳定度”正反馈效应可为MABL内混合层厚度加大在暖水侧升高提供有利条件，有利云区发展。强大的海陆热力差异，可在沿海大气边界层的低层形成次级循环。与次级环流相关的海风和下沉运动有助于水分供应和边界层的降低，有利海雾的形成和维持。分析影响黄海平流冷却雾入侵程度的因素，发现在低层水平上，合理的高、低压配置，使气流持续地从暖湿海面输送到冷海面上，有利于形成深厚的海雾，进而在海风的作用下影响沿海地区。在垂直方向上，边界层内上干下湿的结构，可增强雾顶的长波辐射冷却作用以及雾层内的湍流，有利于海雾的发展与维持；而低层风速增大会引起机械湍流的迅速增长，导致海雾消散。稳定持续的逆温层结构,使水汽在逆温层内累积。海雾影响明显时,对应黄海海域上空的暖平流较强，水汽通量较大,暖湿平流来源于较暖的海面。反之，暖平流较弱，水汽通量较小，暖湿平流来源于较冷的海面。综合来看黄海夏季海雾往往比春季雾对沿海地区影响次数多，程度深。下沉运动和离岸的暖湿气流对岸滨雾的影响至关重要。以上成果在国际学术刊物上发表论文8篇，国内发表论文8篇；并构成学术专著Marine Fog: Challenges and Advancements in Observations, Modeling, and Forecasting 的第六章 Synoptic Processes 的核心内容。

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