Reliability of X-band Dual-polarization Phased Array Radars Through Comparison with an S-band Dual-polarization Doppler Radar

Based on the observations of a squall line on 11 May 2020 and stratiform precipitation on 6 June 2020 from two X-band dual-polarization phased array weather radars(DP-PAWRs)and an S-band dual-polarization Doppler weather radar(CINRAD/SA-D),the data reliability of DP-PAWR and its ability to detect the fine structures of mesoscale weather systems were assessed.After location matching,the observations of DP-PAWR and CINRAD/SA-D were compared in terms of reflectivity(Z_(H)),radial velocity(V),differential reflectivity(Z_(DR)),and specific differential phase(K_(DP)).The results showed that:(1)DP-PAWR has better ability to detect mesoscale weather systems than CINRAD/SAD;the multi-elevation-angles scanning of the RHI mode enables DP-PAWR to obtain a wider detection range in the vertical direction.(2)DP-PAWR’s Z_(H)and V structures are acceptable,while its sensitivity is worse than that of CINRAD/SA-D.The Z H suffers from attenuation and the Z_(H)area distribution is distorted around strong rainfall regions.(3)DP-PAWR’s Z_(DR)is close to a normal distribution but slightly smaller than that of CINRAD/SA-D.The K_(DP)products of DP-PAWR have much higher sensitivity,showing a better indication of precipitation.(4)DP-PAWR is capable of revealing a detailed and complete structure of the evolution of the whole storm and the characteristics of particle phase variations during the process of triggering and enhancement of a small cell in the front of a squall line,as well as the merging of the cell with the squall line,which cannot be observed by CINRAD/SA-D.With its fast volume scan feature and dual-polarization detection capability,DP-PAWR shows great potential in further understanding the development and evolution mechanisms of meso-γ-scale and microscale weather systems.

Regional Prediction of Impending Debris Flow Based on Doppler Weather Radar

Debris flow prediction is one of the important means to reduce the loss caused by debris flow. This paper built a regional prediction model of impending debris flow based on regional environmental background （including topography, geology, land use, and etc.）, rainfall and debris flow data. A system of regional prediction of impending debris flow was set up on ArcGIS 9.0 platform according to the model. The system used forecast precipitation data of Doppler weather radar and observational precipitation data as its input data. It could provide a prediction about the possibility of debris flow one to three hours before it happened, and was put into use in Liangshan Meteorological Observatory in Sichuan province in the monsoon of 2006.

WIND SHEAR IDENTIFICATION WITH THE RETRIEVED WIND OF DOPPLER WEATHER RADAR

Wind shear reflects that the wind field is not uniform, which is one of the primary factors which make the retrieval of the wind field difficult. Based on volume velocity process(VVP) wind field retrieval technique, the intensity of wind shear is identified in this paper. After analyzing the traditional techniques that rely on the difference of radial velocity to identify wind shear, a fixed difference among radial velocities that may cause false identification in a uniform wind field was found. Because of the non-uniformity in wind shear areas, the difference of retrieved results between surrounding analysis volumes can be used as a measurement to show how strong the wind shear is. According to the analysis of a severe convective weather process that occurred in Guangzhou, it can be found that the areas of wind shear appeared with the strength significantly larger than in other regions and the magnitude generally larger than4.5 m/(s·km). Besides, by comparing the variation of wind shear strength during the convection, it can be found that new cells will be more likely to generate when the strength is above 3.0 m/(s·km). Therefore, the analysis of strong wind shear's movement and development is helpful to forecasting severe convections.

Construction, Techniques and Application of New Generation Doppler Weather Radar in China

New generation Doppler weather radar (NEXTRAD) has become one of the most important tools for monitoring and forecasting severe weather. It has been widely used in some developed countries. The construction of China’s NEXTRAD network has started since 1998, and this project is supported by national debt. In this paper the author addresses the development of NEXTRAD techniques, the pre\|sent situation of construction and application of NEXTRAD in China, some problems to be carefully considered in construction, and seve\|ral new fields of future radar technique developments and applications in weather monitoring.

714 SD DOPPLER WEATHER RADAR SYSTEM

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Doppler Radar Analysis on A Local Heavy Precipitation in Jieyang Area of Guangdong

By using Doppler weather radar data,the meso-scale characteristics of extremely heavy rainstorm process which happened suddenly in Jieyang urban area on July 31,2008 were analyzed.The results showed that the radar echo only needed 20 minutes from the generation to the strong echo which quickly strengthened above 50 dBz.The storm center went down south and went up north near Jieyang City all the time.The component which moved eastward was very tiny,and the heavy precipitation echo stagnated.In this heavy precipitation process,the characteristics types of radial velocity which were favorable to the generation and development of heavy precipitation echo appeared alternately each other.The radial velocity's characteristics types were the first type headwind zone,the second type headwind zone,meso-scale convergence type and cyclonic convergence and so on.Thus,this heavy precipitation process which broke the record happened.The analyses showed that the headwind zone which developed vigorously and the convergence which had influx and outflux airflow in the vertical direction of headwind zone made obvious contributions to the precipitation.

A Model Study of Three-Dimensional Wind Field Analysis from Dual-Doppler Radar Data

A three-dimensional wind field analysis sollware based on the Beigng-Gucheng dual-Doppler weather radar system has been built, and evaluated by using the numerical cloud model producing storm flow and hydrometeor fields. The effects of observation noise and the spatial distribution of wind field analysis error are also investigated.

Research and Implementation of a Graphic System for Doppler Radar

Doppler radar have become one of the most important instruments for weather now casting,and for meso-scale weather research because of its higher spatial and temporal resolutions. A dealing system for Doppler radar graphic was researched and implemented so as to providing a convenient tool for users. We research and realized CINRAD/XD Doppler radar's graphic system. It contains three important parts:reading,standardization and pretreatment. It can be used very easily and conveniently. Besides,the system can be expanded and transplanted simply.

Microphysical and Dynamical Climatology of Precipitating Systems Inferred by Weather Radar Polarimetric Measurements in Brazil

This work presents the climatology of the microphysics and the dynamics of weather systems in two coastal areas of São Paulo and the Espírito States at high spatial-temporal resolution as measured by two dual Doppler weather radars during the summer and early fall of 2015. Averages and respective standard deviations of polarimetric variables, namely, reflectivity (Z), differential reflectivity (ZDR), differential phase (ϕDP), specific differential phase (KDP), copolar correlation coefficient (ρoHV), radial velocity (Vr), and the spectral width (W) were obtained within a 240-km range on plan position indicator (PPI), constant altitude plan position indicator (CAPPI) and vertical cross-sections to analyze overall horizontal and vertical precipitation microphysics and mesoscale circulation of prevailing weather systems, and their peculiarities over coastal and oceanic, and urban and rural areas. Overall, raindrops tend to be larger over the Metropolitan area of São Paulo from the surface to up to 6 km altitude indicating more vigorous updrafts caused by the heat island effect and the local sea breeze. The vertical microphysical structure is remarkably distinct over the Metropolitan Area of São Paulo (MASP) where thunderstorms can reach 20-km altitude in summertime under sea breeze and heat island effects. On the other hand, there is a dominancy of smaller drop sizes though larger ones observed close to the surface by the coast of Espírito Santo and at the land-ocean interface influenced by the local low-level jet and oceanic-type CCN. Convective cells tend to be smaller associated with Easterlies and more organized with Westerlies. The results indicate distinct features on hydrometeor types and circulation characteristics under these different surface and boundary-layer conditions in close agreement with previous results in the literature.

基于改进Marching Cubes算法的雷达气象数据三维重建

在气象领域中,多普勒天气雷达探测到的气象数据采用以雷达站点为原点的三维极坐标系进行存储,具有形状不规则、数据量大等特征。Marching Cubes(MC)算法是三维重建中的经典算法,但应用于气象领域时存在重建效率低下和不能直接处理气象数据的缺点。为了实现气象数据的三维重建,基于MC算法提出雷达数据归一化处理与状态标记判别算法NBV-MC。该算法根据雷达基数据文件的特点对其进行归一化预处理,使用雷达基数据构建拟梯形六面体体素,对每一个六面体体素进行状态标记,在遍历六面体体素时动态判别其是否需要处理。实验结果表明,NBV-MC算法不仅解决了由于气象数据具有不规则性而不能直接用于MC算法的问题,而且可以在保证数据真实性和重建效果的情况下有效减少绘制等值面所需要的三角面片数量,提高重建速度。与MC算法相比,NBV-MC算法的重建效率提升了77.70%以上,有利于实时场景交互,便于气象研究人员直接分析雷达数据。

一种基于谱连续的极化-多普勒气象雷达信号重构方法

谱极化滤波技术广泛应用于气象雷达杂波抑制中,但是当地杂波与降雨目标混叠时,这些方法在滤除杂波的同时会损失气象信息。针对这一问题,提出一种基于谱连续的极化-多普勒气象雷达信号重构方法。该方法利用气象回波和杂波在距离-多普勒图上的特征差异实现气象目标的保留和杂波的滤除。具体是利用气象目标的多普勒速度和谱宽的空间连续性,采用多项式拟合和高斯拟合的方法补偿降雨区域。业务气象雷达实测数据验证了所提方法的有效性。

基于贝叶斯分类器和回波物理特征的C波段雷达非气象回波识别方法和性能分析

天气雷达在观测过程中,通常会受到非气象因子的干扰,产生非气象回波,从而严重影响雷达定量降水估计的精度和短临降水预报的性能。本文使用陕西省西安、延安等7部C波段多普勒天气雷达的体扫观测,构建了基于贝叶斯分类器和回波物理特征的质量控制方法:首先人工提取每部雷达的降水回波、地物回波和晴空回波的反射率因子,并基于提取的不同类型雷达回波,分析了陕西省7部雷达不同类型雷达回波的反射率因子、反射率因子水平纹理、反射率因子沿径向的变化梯度、5 dBZ回波高度、反射率垂直梯度的变化特征,统计得到不同类型雷达回波对应特征量的概率密度分布函数;然后基于统计的概率密度分布函数建立贝叶斯分类器,对雷达回波进行初步识别;在此基础上,结合雷达回波物理特征设计了太阳尖峰识别方法、孤立点去除方法和回波空洞填补方法,进一步识别雷达回波;最后去除非气象回波,得到质量控制后的降水回波数据。利用2019年7~9月陕西省7部雷达的体扫观测数据,系统地分析了雷达质量控制方法的性能,同目前陕西省业务运行的雷达数据质量控制结果进行了对比分析,并使用HSS评分(Heidke skill score)评估了质量控制结果的准确率。结果表明,研发的基于贝叶斯分类器和回波物理特征的雷达质量控制方法能够较好地识别降水回波和非降水回波,识别效果优于业务使用结果,7部雷达数据质量控制结果的HSS评分均在0.75以上。

基于雨滴谱参数反演的C波段双偏振雷达降水类型分类方法

降水类型分类对分析区域降水微物理特征、多源降水融合误差模型的构建以及雷达定量测量降水估计等都很重要。本文基于2015~2016年南京信息工程大学C波段双偏振雷达数据和南京地区滴谱仪观测资料,提出一种适用于南京地区的雷达降水类型分类方法,并对降水类型分类结果进行对比验证。首先,基于滴谱仪降雨率时序数据、地基雷达反射率因子平面位置显示数据和地基雷达反射率因子时间—高度显示数据,筛选出36次典型层状和对流降水过程。随后,统计3个滴谱仪站点典型层状(对流)降水的雨滴谱(DSD)参数,拟合得到适用于南京地区的降水类型分类线。将基于滴谱数据统计拟合的分类线应用于基于变分法反演的地基雷达DSD参数,进行地基雷达降水类型分类。根据典型层状(对流)过程降水类型分离指数的时间—高度分布,并对比星载双频测雨雷达(DPR)降水分类产品,对分类效果进行验证。最后,将分类结果应用于雷达分类定量降水估计,进一步说明降水分类的应用效果。结果表明,南京地区3个滴谱仪站点的拟合分类线非常一致,3个站点的典型层状(对流)过程均能够很好地分离在分类线两侧;与DPR降水分类产品进行对比分析,发现南京地区分类线的分类效果相对于其他典型降水分类方法,对层状和对流降水的识别率整体最高,分别为84.56%和72.64%;基于降水分类的雷达定量降水估计的测雨精度均优于未分类的测雨公式,且基于差分传播相移率的测雨公式[R(KDP)]在四种分类测雨公式中整体性能最优,基于水平反射率因子的测雨公式[R(ZH)]在层状云降水反演中性能最优,基于差分传播相移率的测雨公式[R(KDP)]在对流云降水反演中性能最优,基于水平反射率因子和差分反射率的测雨公式[R(ZH,ZDR)]对原有总体测雨公式降水精度的提升最为明显。

天山北坡“20080826”超级单体的Doppler雷达资料分析

利用石河子C波段Doppler雷达资料,对2008年8月26日下午至傍晚发生在天山北坡带中部石河子垦区全区性的一次强对流天气过程进行分析,结果表明：引起这次全区性的强对流天气风暴具有超级单体风暴的特征。这个超级单体南边出现明显的出流边界,并位于弧形回波带的南部。组合反射率因子垂直剖面图上呈现出有界弱回波区、回波悬垂和有界弱回波区左侧的回波墙,最大回波强度出现在沿着回波墙的一个竖直的狭长区域,其值达到65 dBZ、位于回波墙中上部。在中低层径向速度图上,弧形回波带的北部出现辐合区,其东南部呈现出一个中尺度气旋,旋转速度达到20 m/s,风暴顶为强烈辐散,正负速度差值达52 m/s,其中3 000~6 000 m之间表现最为典型;与中气旋对应的回波强度和回波顶高以及垂直液态含水量都在暴雨中心附近达到最大。50dBz的回波顶高达9.8 km、宽度约10 km,60 dBz的回波顶高达到8.7 km、宽度约7 km,65 dBz的回波顶高达到8.0 km、宽度约2 km,垂直液态含水量从16∶16的8 kg/m跃增到17∶34的70 kg/m,该超级单体的移动方向在盛行风向的右侧约30°,属于右移风暴。

多普勒雷达V型缺口特征在冰雹预报预警中的应用分析

利用山西4部C波段多普勒天气雷达基数据和地面观测资料,对2009-2017年山西出现的38次多普勒雷达V型缺口特征进行统计分析,研究多普勒雷达V型缺口特征与降雹的对应关系,总结V型缺口对冰雹的预报预警指标,并在2018-2022年开展实时业务应用,对V型缺口特征及预报预警指标进行检验并订正。结果表明:降雹在V型缺口出现后开始,在V型缺口消失前结束;降雹概率与V型缺口起始高度无明显的对应关系;V型缺口对应的上升气流高度≤4 km时无降雹;V型缺口理想的观测仰角为2.4°~6.0°,最佳观测仰角为2.4°;强回波区呈现“蝴蝶状”是降雹最强阶段。降雹开始阶段预报预警指标及关注点:(1)V型缺口有弱回波区或有界弱回波区;(2)初始V型缺口沿径向长度>30 km,当≤30 km时上升气流伸展高度要超过4 km;(3)平均径向速度具有低层辐合高层辐散特征。满足以上3点可预报有冰雹出现,如果V型缺口首先在6.0°仰角观测到,可预报有大冰雹出现(直径大于1 cm),并立即发布预报预警信号。冰雹持续期间预报预警指标及关注点:(1)>50 dBZ强回波中心连续下降且回波顶高>10 km;(2)V型缺口对应的弱回波区呈倾斜状;(3)弱回波区或有界弱回波区稳定维持;(4)当在0.5°仰角观测到V型缺口时可预报冰雹仍在持续;当强回波区呈现“蝴蝶状”,可预报降雹强度增强;(5)当V型缺口最大垂直液态水含量>22 kg·m^(-2)、垂直液态水含量跃增量>26 kg·m^(-2)、垂直液态水含量密度>3.6 g·m^(-3)时,出现冰雹的概率较大。

基于相控阵多普勒雷达技术的强对流天气预警系统设计

为了避免突发性灾害对人身以及财产安全造成的影响,针对天气预警过程的干扰因素较多、雷达成像像素精度较低等问题,设计基于相控阵多普勒雷达技术的强对流天气预警系统。设计数据采集芯片和电路混频器,通过不同的电压获取双通道接口的稳定运行。基于相控阵多普勒雷达技术,采集强对流天气数据并进行前期处理,通过多普勒雷达格式数据计算水平反射率结构以及梯度垂直反射率,避免干扰因素影响,计算最大模糊速度与最大模糊距离,得到雷达退速度模糊参数,建立强对流天气预警模型,得到一个新的强对流天气预警系统。实验结果表明,该系统所得到的不同径向距离以及不同方位角度的像素精度均小于0.03,提高雷达成像精度可以得到更准确地预警结果。

风廓线雷达与多普勒天气雷达在暴雨大风天气过程中的应用分析

文章简述了风廓线雷达与多普勒天气雷达在实时监测、数据采集、预警系统集成方面的理论基础,通过对广元地区一次强对流天气过程进行研究,探讨了风廓线雷达与多普勒天气雷达在暴雨大风天气过程中的应用。结果表明:受高原低值系统和低层暖湿气流的共同影响,配合副热带高压588线位置稳定少动,以及地面冷空气入侵,有利于暴雨大风天气的发生;强降水中心落区与多普勒天气雷达的片状混合云回波带和风速辐合区较一致;风廓线雷达垂直风场中垂直风向的转变和水平风速的加快能有效揭示对流天气的发生和发展过程。

衢州暖季雷暴大风天气时空分布及雷达特征统计

【目的】为总结对衢州雷暴大风预警有指示作用的本地化雷达预报指标。【方法】利用2017-2021年衢州地区地面加密观测资料、闪电定位仪及CINRAD-SA波段雷达资料,选取29次雷暴大风过程,分类分析了衢州地区不同环流形势下雷暴大风出现前的雷达产品特征。【结果】(1)衢州暖季雷暴大风时空分布不均匀。中部盆地区域明显多于山区;3月、5月、7月雷暴大风影响区域范围较大;日变化明显,高频时段为中午至前半夜。(2)根据天气形势配置,衢州地区雷暴大风可分为副高边缘型、暖湿平流强迫型、锋生切变型、干冷平流强迫型等4类。(3)衢州地区产生雷暴大风的雷达回波主要为块状回波、弓形回波、带状回波等3类,其中块状回波出现最多。(4)不同对流组织类型的雷达回波,雷暴大风的预警指标不同。依据低层径向速度大值区和中层径向速度辐合可以对弓形回波产生的雷暴大风提前预警;依据低层径向速度大值区、垂直积分液态水含量(VIL)的跃增能对带状回波雷暴大风天气提前预警;仅有36%的块状回波个例中提前出现了低层径向速度大值区,但是VIL的跃增及回波顶高的跃增可以提前预警块状回波雷暴大风的出现。【结论】上述结论可为做好衢州地区雷暴大风的短时预报及临近预警工作提供参考。

An Algorithm on Convective Weather Potential in the Early Rainy Season over the Pearl River Delta in China

This paper describes the procedure and methodology to formulate the convective weather potential （CWP） algorithm. The data used in the development of the algorithm are the radar echoes at 0.5° elevation from Guangzhou Doppler Radar Station, surface observations from automatic weather stations （AWS） and outputs of numeric weather prediction （NWP） models. The procedure to develop the CWP algorithm consists of two steps： （1） identification of thunderstorm cells in accordance with specified statistical criteria; and （2） development of the algorithm based on multiple linear regression. The thunderstorm cells were automatically identified by radar echoes with intensity greater than or equal to 50 dB（Z） and of an area over 64 square kilometers. These cells are generally related to severe convective weather occurrences such as thunderstorm wind gusts, hail and tornados. In the development of the CWP algorithm, both echo- and environment-based predictors are used. The predictand is the probability of a thunderstorm cell to generate severe convective weather events. The predictor-predictand relationship is established through a stepwise multiple linear regression approach. Verification with an independent dataset shows that the CWP algorithm is skillful in detecting thunderstorm-related severe convective weather occurrences in the Pearl River Delta （PRD） region of South China. An example of a nowcasting case for a thunderstorm process is illustrated.

Analysis on an Easterly Wave Thunderstorm and Gale Weather during the Latter Flood Season of 2010

[Objective] The research aimed to analyze an easterly wave thunderstorm and gale weather during the latter flood season of 2010.[Method] Based on conventional observation data,data of automatic station,NCEP 1°×1° reanalysis data,Doppler radar reflectivity and radial velocity data,the easterly wave thunderstorm and gale weather process which happened during 4-5 August,2010 was analyzed.The circulation situation,wind field and dynamic & thermal structures of easterly wave,echo characteristics of Doppler radar when thunderstorm and gale happened were studied.[Result] The thunderstorm and gale weather happened in the northeaster zone in front of the deep thick easterly wave trough.When thunderstorm and gale weather happened,position of the subtropical high was by north(ridge line was at 35° N).Eastward movement of the north branch of trough compelled subtropical high splitting into east and west circles.Westward extension of the east subtropical high and saddle-type field circulation were favorable for generation and development of the easterly wave.As development and westward movement of the easterly wave,in the influence zone in front of the trough,upper easterly component transmitted downward.Then,low-level northeaster obviously strengthened,and thunderstorm and gale weather appeared.In the zone where thunderstorm and gale happened,airflow had cyclonic convergence at the middle and low layers and anti-cyclonic divergence near the ground layer.Subsidence movement was obvious.Moreover,thermal force structure that it tended to be dry and cold at the middle and high layers,warm and wet at the low layer existed.Supercell storm was at the developed stage on 4th.It had obvious mesocyclone and hooked echo characteristics(meso-and small-scale characteristics).Characteristics of the squall line,gale region and adverse wind region appeared in central west Guangdong on 5th.Doppler characteristics of the mesocyclone,hooked echo,squall line,gale region and adverse wind region had indication significance for short-imminent forecast of the thunderstorm and gale.[Conclusion] This research revealed some information which had significance for forecasting local easterly wave thunderstorm and gale weather.