江苏北部龙卷雷达组网探测策略

Observation Strategy of Tornado Radar Network in Northern Jiangsu

为了探测、分析和研究尺度小、生命史短、致灾重的龙卷等强对流天气三维精细化垂直结构及演变规律,江苏正在龙卷易发区苏北平原建设高时空分辨率的双偏振雷达网。本文为支撑苏北龙卷雷达网建设,从龙卷雷达组网的必要性出发,重点分析苏北龙卷雷达组网策略。研究表明:(1)苏北龙卷雷达网拟采用大天线、全固态、高性能技术指标的X波段双偏振雷达组网,采用不同的观测模式,可获得空间一致性好、时空分辨率高且丰富的探测数据,满足龙卷等强对流天气的快速、精细化探测要求。此外,采用较高的脉冲重复频率等扩展测速范围,解决X波段雷达速度模糊问题。(2)经理论计算与比较,苏北龙卷雷达网可采用正三角形组网拓扑结构,取累计空间密度值90%,雷达间距为60km时,波束直径bs特征值为282.0m,最低波束高度bh特征值为52.6m,探测灵敏度Zmin特征值为2.7dB;X波段雷达组网与S波段业务雷达相比,在60km探测距离处,其波束直径减小了约2倍,0°仰角盲区高度降低了约1.5倍,探测灵敏度降低了2.4dB。即在方位分辨率、探测盲区、弱回波探测能力、数据空间一致性等方面均得到提升,可提供更多低于1km、甚至百米的高时空分辨率的雷达资料,便于捕捉龙卷等强对流天气。(3)苏北龙卷雷达网在盐都、阜宁、大丰、宝应、兴化(龙卷易发区),各布设一部固定式X波段全固态双偏振多普勒天气雷达。综合考虑在苏北平原雷达选址的各种因素,最终雷达网基本单元拟采用近似正三角形(N=3,L=45~65km)的拓扑结构。5部高时空分辨率的龙卷探测雷达组成3个近似正三角形的单元,镶嵌在S波段雷达业务网内(盐城、淮安、泰州雷达中间)。后续可进一步增加雷达数量及拓宽观测区域,例如在高邮等龙卷易发地区,可增补X波段天气雷达或C波段相控阵天气雷达。

In order to detect and analyze the three-dimensional fine structure and evolution law of severe convective weather such as tornado with a small scale,short life cycle and heavy disaster,Jiangsu is building a high-resolution dual polarization weather radar network in the North Jiangsu Plain,where tornadoes occur freguently.This paper focuses on the networking strategy of the tornado radar network in the northern Jiangsu to support the construction of the tornado radar network.The study shows:(1)The tornado radar network in the northern Jiangsu adopts the X-band weather radar(dual polarization)network with large antenna,all solid state and high performance,and high performance indexes,which can not only realize long-distance detection,but also obtain data products with a great deal of high spatial consistency and high spatial-temporal resolution data,to a large extent meeting the requirements of fast and fine detection for tornadoes and other severe convection weather.In addition,in order to overcome the problem of velocity ambiguity for X-band weather radar,a higher pulse repetition frequency can be used to expand the speed measurement range.(2)In the North Jiangsu tornado radar network,a triangle(N=3,L=60km)network topology is used for theoretical calculation.When the cumulative spatial density value is 90%,the performance indicators are:beam size bsis 282.0 m,the minimum beam height bhis 52.6 m,and the detection sensitivity Zminis 2.7dB.Compared with the single S-band operational radar,the beam size of X-band network radar in the northern Jiangsu has reduced by about 2times,the minimum beam height by about 1.5times,and the detection sensitivity by about 2.4dB.That is to say,the azimuth resolution,detection blind area,weak echo detection ability,and data spatial consistency have been greatly improved,which can provide more radar data with a high spatial resolution,less than 1km or even 100m,high weak echo detection capability,and high spatial consistency.All that is convenient for monitoring,forecasting,and early warning of severe convective weather such as tornadoes.(3)Five X-band all-solid-state dual polarization Doppler weather radar sets are respectively equipped in Yandu,Funing,Dafeng,Baoying,and Xinghua(tornado-prone areas),which forms the tornado radar network in the northern Jiangsu.Considering the various factors of radar location selection in the North Jiangsu Plain,the basic unit of the final network adopts the topology structure of approximate triangle(N=3,L=45-65km).The high spatial-temporal resolution tornado detection radar network is composed of three basic networking units,which is similar to a trapezoid structure,embedded in the S-band radar service network(equipped in Yancheng,Huai’an,Taizhou,respectively).In the future,the number of radar sets can further increase and the observation area can be widened.X-band weather radar or C-band phased array weather radar can be added in the tornado prone areas such as Gaoyou.