渤海西岸及近岸海域准圆形MαCS多尺度结构及演变的研究

The α- meso-scale convective system (MαCS)with quasi-circular cloud top is an important system which can cause severe convective weather such as rainstorm, thunderstorm wind, hail and lightning, etc. It frequently occurs on western coast of Bohai Bay and offshore areas with some characteristics such as suddenly occurrence, great damage and wide scope of influences. It is hard to be predicted. Its internal structure is various and its evolution is complicated and organizational. In this project, the methods of superposition and fusion of multiple data, radar wind field inversion, radar quantitative parameters, meso-scale filtering and meso-scale numerical simulation were employed and quantitative data of satellite (TBB products inversed by infrared channel and all kinds of radiation data ), quantitative data of radar and other new type of detection data(L-band sounding, the wind profile radar, automatic weather station data, microwave radiometer, lightning positioning system),offshore platform data, buoy station data and the wind tower observation data were used to analyze the meso-scale environment background of multiple kinds of MαCS and the evolutions of organizational, dynamic and thermal structure and mechanism of multi-scale convective systems (especially MγCS) during their initialization, development, maturation and dissipation phases. Meanwhile the influences of underlying surface on the evolution of system structure and the relationship between the evolution of structure and severe weather were also analyzed. Finally, the organizational, dynamic and thermal configuration and evolution conceptual model was established and forecasting focus and the harbingering indicators of various data were provided in this project which can supply factual basis and technical support for accurately forecasting of severe convective weather.

具有准圆形云顶的MαCS是造成对流性暴雨、大风、冰雹、闪电等灾害天气的重要系统，其内部结构多样、演变复杂且有组织性，所造成的灾害天气破坏力强、影响范围广、预报难度大；且其在渤海西岸及近岸海域多有出现。本项目重点利用卫星的定量数据（红外通道反演TBB产品和各种辐射量)、雷达定量数据及其他新型探测资料（L波段探空、风廓线、自动站、微波辐射仪、闪电定位）、近海平台、浮标站、风塔观测资料，采用多资料融合叠加、雷达风场反演、雷达量化参数、中尺度滤波、中尺度数值模拟、中分析图等方法，研究多种类型准圆形MαCS及中尺度背景；研究发生、发展、成熟、消亡各阶段多尺度对流系统的组织、动力、热力结构演变及机制；研究结构演变与灾害天气的联系；研究近岸海域水体及潮流下垫面对系统结构演变的影响。建立组织、热力、动力配置及演变概念模型，给出预报着眼点及各种资料的先兆指标，为强对流天气的精确预报提供依据。

渤海西岸及近岸海域的天气系统既受北侧燕山山脉、西侧太行山山脉的影响，也有来自其东侧渤海、黄海的作用。在上述地区的多尺度强对流天气系统中，准圆形MαCS是有组织的、重要的α-中尺度对流系统，它影响范围广、生命史长、危害性大，且内部结构多样、演变复杂，是预报业务的难点和重点。 .利用再分析资料和多种观测资料，采用资料叠加、参数、中尺度滤波等诊断手段和模拟方法，研究MαCS发生、发展的环境背景，剖析多尺度系统的组织、动力、热力结构演变及成因机制；认识渤海地形、浅海水面和潮流等与多尺度系统演变的关系。给出概念模型图和预报着眼点。.研究成果如下：1）按照限定标准普查2005-2018年对流系统，获得51个准圆形MαCS样本，建立了灾情库和雷达卫星图库；针对环流形势分为华北冷涡型（13个）、高空槽型（13个）、副高边缘型（12）和东北冷涡型（13个），并绘制高低空环流合成图；计算筛选多种热力动力等对流参数，通过箱线图分析，给出垂直风切变、低空南风和东风、CAPE和比湿等环境参数在准圆形MαCS发生、发展和成熟阶段的变化特点以及在发展-成熟阶段各类型环境参数的最优特征。给出不同类型的水汽追踪图和中分析图。2）对39个准圆形MαCS的组织结构进行了分型（线状25、锢囚状4、混乱状10）；采用扰动图叠加红外亮温TBB的方法，通过18个样本证明了200hPa存在的扰动风场（反气旋性、气旋性和发散性）对准圆形MαCS圆形云顶的形成及其变化有重要的影响。给出空间结构概念模型图。3）通过多个样本的诊断和模拟研究表明：南风低空急流、西北风冷空气和冷池出流、来自渤海的浅层东风（昼冷湿，夜暖湿）在研究区域灾害性天气的落区、强度中起着关键性作用。并通过对渤海西岸强降水出现前期偏东风出现的时长、频率、风向等的统计分析得到证明。4）数值模拟结果表明：用RKW理论解释了飑线系统在入渤海后增强的原因，光滑的渤海水面对西南风有增强效应；夜间渤海水面的感热、潜热交换的海陆差异及其对近地面辐合线的位置、垂直流场和大气层结的影响均不明显。5）卫星资料多通道差、梯度对强天气有预警意义，风廓线给出的垂直风连续演变，揭示低空急流及水平风的垂直切变在灾害天气中具有广泛的应用价值。6）项目创新研发的识别技术和回波参数法，对今后计算机自动识别和短时临近预警均有积极意义。