基于雷达和卫星低纬高原强对流风暴演变及闪电特征研究

Yunnan locates in Lower Latitude Plateau of China. Strong convective disaster weather such as short-time strong precipitation, thunder storm, gale and hailstone frequently occurs and results in serious disaster. Because strong convective weather has characteristics of small space-time scale, strongly sudden occurrence, general synoptic chart is difficult to catch and forecast it. But Doppler weather radar and meteorology satellite detect with high space-time resolving capability and can directly identify mesoscale strong convective storm well and truly which produces strong convective disaster weather. In the mean time, lightning may also direct the occurrence and development of strong convective storm ahead. By new generation observational data of Doppler weather radar in Yunnan and meteorological satellite, evolutive characteristics of radar echoes and satellite pictures and quantificational indexes of different strong convective storms are studied respectively in Lower Latitude Plateau of China by the item. By combining with monitoring data of lightning detection system, the space-time distribution characteristics，polar characteristics and evolutive rules in the course of the development and evolutiion of strong convective storms are studied, and diagnostic indexes and threshold values of radar echoes and satellite pictures during lightning occurrence are also researched. Thereby the structure characteristics and evolutive rules of strong convective storms may be opened out, and warning models and evolutive functions which lightning frequency changes with time will be built for different styles of strong convective storms. Not only this can establish basis for application and study of multiform new generation observational data on strong convective storms in Lower Latitude Plateau of China and learned articles of high quality will be published, but also researchful results can apply to practice and can enhance ability of warning and forecasting strong convective disaster weather.

云南地处低纬高原，短时强降水、雷雨大风、冰雹等强对流灾害性天气频发，致灾重。强对流天气具有时空尺度小、突发性强等特点，常规天气图较难捕捉，预报难度大，多普勒天气雷达和气象卫星探测时空分辨率高，能直观准确地识别产生强对流灾害性天气的中小尺度强对流风暴，且闪电又可提前指示强对流风暴的发生和发展。本项目通过云南多普勒天气雷达、气象卫星等新一代探测资料对低纬高原不同强对流风暴的雷达回波和卫星云图演变特征及定量化指标进行研究，并结合闪电定位系统监测资料研究强对流风暴发展演变过程中闪电的时空分布特征、极性特征和演变规律及闪电发生的雷达回波和卫星云图特征指标和阈值，从而揭示强对流风暴的结构特征和演变规律，并建立不同类型强对流风暴闪电随时间的演变函数和预警模型，不仅为新一代探测资料在低纬高原强对流天气中的应用研究奠定基础，发表高质量学术论文，研究成果还可在实际中应用，提高强对流灾害性天气的预警预报能力。

项目利用大气环流、气象卫星、多普勒天气雷达和地闪定位系统等资料，采用个例分析、聚类分析、诊断分析、统计分析、相关分析等方法开展强对流风暴演变和地闪特征及成因研究，严格按照计划进行，完成了研究内容和目标。研究表明：云南强对流雷暴天气自南向北减少且季节差异大，并呈现两峰两谷日变化特征。川滇切变、南支槽、两高辐合、南海低压与热带辐合带、西太平洋台风提供高能高湿和不稳定大气环流条件，近低层中尺度辐合线诱发强对流风暴发生，高空环境风垂直分布影响强对流风暴空间结构。小对流单体不断长大、有规律排列、相互合并发展成单单体风暴、多单体风暴、飑线、MCC或超级单体，在发展到成熟阶段，TBB下降，回波强度增强、顶高和强回波高度增大，结构密实和不均匀，并具有后侧“V”槽口、前侧“V”缺口、弱回波区、阵风锋回波、钩状回波、中气旋、中尺度径向辐合、回波墙、假尖顶回波、悬挂回波和径向大风等特征，地闪频增和剧烈，产生冰雹大风和短时强降水等强对流天气，到成熟阶段后强对流风暴顶部出现卷云砧，TBB缓慢下降，回波强度减小，回波顶高和强回波高度降低，变得均匀和松散，地闪减弱，以产生短时强降水天气为主。强对流风暴对流状况和地闪密度具有前侧对流发展型、中间对流型、后侧对流发展型等特征，而且地闪频数随时间具有峰谷演变特征，强对流风暴发展强度和地闪与TBB和雷达回波特征指标有较好的相关关系，发展到TBB≤-42 ℃、回波强度≥40 dBz、顶高≥9 km、30dBz强回波高度≥-10℃高度、VIL≥10 kg/m2时地闪开始，进一步发展到TBB≤-45 ℃、回波强度≥55dBz、顶高≥11 km、VIL≥15 kg/m2时，冰雹大风才会产生，密集地闪和强天气发生在TBB≤-52 ℃的低中心及梯度大值区及回波强度≥40 dBz和顶高≥10 km的强回波区内及中尺度不均匀风场附近，正地闪分布范围更广。研究工作获得了对强风暴结构特征、演变规律和形成成因的发现和认识，成果应用于强对流天气短时临近预警模型和系统，改进了暴雨和冰雹等强对流天气监测预报能力。