共查询到19条相似文献，搜索用时 109 毫秒
1.
为了进一步认识冰雹和三体散射的双线偏振雷达观测特征,提高业务预警能力和奠定基于双线偏振雷达的地面降雹识别基础,利用南京双线偏振雷达观测资料,统计分析了2019年3月20日冰雹过程发展、成熟和降雹阶段的观测特征及微物理过程。结果表明:（1）雹暴在成熟阶段具有高悬的强回波中心和较高的顶高,强回波中心差分反射率ZDR＜?0.5 dB,相关系数（ρhv）约为0.9,由于冰雹后向散射相位的影响,该区域比差分相位（KDP）呈现负值,指示了该区域有冰雹存在,并被相态分类算法（HCA）正确识别;（2）降雹阶段,高层反射率因子减小,强回波中心下降到地面附近,融化层以下ρhv增大,指示高层下落的冰相粒子整体尺寸减小;HCA识别到冰雹开始减少时,地面观测到冰雹;（3）三体散射的反射率因子（ZH）、ρhv和反射率因子标准差（SD（ZH））概率密度分布与北美三体散射比较接近;ZDR分布更偏向于负值区域,差分相位标准差（SD（φDP））分布范围大约是北美结果的2倍。 相似文献
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利用中国气象科学研究院灾害天气国家重点实验室的车载C波段双线偏振多普勒雷达 (C-band Polarimetric Doppler Radar on Wheel,CPDRW) 的外场试验,在统计分析降水、地物回波差分传播相移ΦDP数据的差别与信噪比关系等基础上,提出了一套数据分析和处理的方法。该方法通过ΦDP的异常波动并结合回波的强度ZH和速度Vr信息将地物回波信号分离出来,在降水估测或衰减订正等定量应用时将其剔除。对于气象回波则根据信噪比及零滞后互相关系数ρHV(0) 将ΦDP资料分为较好、较差和差3类。对于较好数据直接进行后续的预处理,对于较差数据先订正后处理,而对于差数据将其剔除以保证ΦDP资料的整体质量。经过大量资料的验证,该方法在最大程度上保留气象信息的同时也保证了ΦDP资料的质量,并能估算出质量较高的差分传播相移率KDP资料。 相似文献
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选取2020年3—9月深圳求雨坛的X波段双偏振相控阵雷达探测数据, 与同位置的S波段双偏振雷达进行对比。通过一定限制条件定量分析引入误差的原因, 发现反射率因子ZH和差分反射率ZDR的标定误差和随机误差较大, 其中ZH误差变化范围为-0.5~4.5 dB, ZDR误差变化范围为-0.7~0.2 dB。在上述较大误差影响下, 传统模糊逻辑相态识别方法的水凝物相态识别结果不可靠, 因此根据不同相态的雷达参量特征范围以及融化层高度建立基本结构为二叉树的决策树相态识别方法。针对上述方法的实际应用效果, 分别从水凝物相态识别结果对误差的敏感性和空间分布的合理性进行评估, 结果表明: 决策树相态识别方法的水凝物相态识别结果稳定性高于模糊逻辑相态识别方法, 且在对流云中的水凝物相态分布更加合理, 能够发挥X波段双偏振相控阵雷达在研究云内水凝物相态演变的优势。 相似文献
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利用MICAPS高空地面资料和湛江S波段双偏振雷达资料对2019年3月6日、4月12日共4次雹暴云团造成的降雹天气过程进行分析。结果表明：1)4次过程均出现高悬强回波、三体散射长钉等降雹强风暴基本雷达特征；2)双偏振雷达基本参量的冰雹识别通常以高水平基本反射率ZH、低的差分反射率ZDR、协相关系数CC作为冰雹主要识别判据。3)4次雹暴云团在入流缺口处有明显的ZDR环和ZDR柱。成熟的雹暴云团强回波区对应ZDR为趋近于0 dB的低值区，低于0.95的CC与趋近于0 (°)/km或为缺测的KDP。4次过程中降雹前1～2 h,雹胚发展的强回波区域对应ZDR常有低值窄带区下延接地。 相似文献
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为提高X波段双偏振相控阵雷达(XPAR-D)数据质量,采用自适应约束订正方法对反射率因子ZH、差分反射率因子ZDR进行质量控制;利用广州S波段双偏振雷达(CINRAD/SAD)和地面二维雨滴谱观测对XPAR-D雷达的数据质量进行分析,结果表明XPAR-D雷达与CINRAD/SAD雷达的回波强度基本一致,由于XPAR-D雷达灵敏度较低,导致对弱回波的探测能力低于CINRAD/SAD雷达。将XPAR-D雷达测量的反射率因子ZH与雨滴谱仪反演的ZH对比,两者相变化趋势基本一致;XPAR-D雷达差分反射率ZDR、差分相移率KDP与ZH的一致性较好,其中KDP约是CINRAD/SAD雷达的3.3倍;XPAR-D雷达偏振参量能有效反映融化层的偏振特征;一次局地性强降水的观测结果表明相控阵雷达能够精细监测降水的触发、演变过程以及不同降水强度的微物理特征。 相似文献
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C波段双偏振多普勒天气雷达资料分析及在定量估计降水中的应用研究 总被引：5，自引：5，他引：5
基于南京信息工程大学C波段双线偏振多普勒天气雷达(NUIST-CDP)的观测资料,结合南京龙王山SA天气雷达数据、南京信息工程大学大气综合观测基地的OTT Parsivel雨滴谱仪数据、南京市地面雨量计数据,分析NUIST-CDP探测资料的质量及定量降水估计(QPE)精度情况。将NUIST-CDP与SA雷达的回波强度数据进行了对比,发现NUIST-CDP回波强度偏弱;将滴谱仪上方NUIST-CDP测量的反射率因子ZH、差分反射率因子ZDR与滴谱仪数据对比,雷达参量ZH、ZDR与滴谱仪数据变化趋势一致,但整体略偏小;比较差分传播相移率KDP与ZH的变化情况,由差分传播相移ΦDP经最小二乘法计算得到的KDP与ZH数据一致性很好。利用南京地区2015年夏季(5—8月)收集的滴谱数据计算偏振雷达参数,拟合测雨方程,进行两次降水过程个例的QPE分析,并与南京地区雨量计数据进行了对比。结果表明:R(KDP)测雨精度最高,R(KDP,ZDR)次之,使用偏振参量能明显提高降雨估算精度;R(ZH)、R(ZH,ZDR)方法测雨反演结果低于地面雨量计雨量值,且低于SA雷达反演结果。 相似文献
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双线偏振多普勒雷达资料质量分析 总被引：12，自引：5，他引：7
以中国气象科学研究院灾害天气国家重点实验室的车载C波段双线偏振多普勒雷达（CPDRW）2011年完成升级改造后观测的一次大范围层状云降水过程资料为例,讨论了该设备改造后探测资料质量的改进情况及其对降水粒子的探测性能,同时利用模糊逻辑法结合地物的常规特性和偏振特性,建立了一种运用双线偏振雷达观测资料识别地物及地物与降水混合回波的方法,并利用该雷达的观测资料对识别结果进行了分析检验,最后统计分析了降水回波的差分反射率因子(ZDR)、零滞后互相关系数(ρHV（0）)与信噪比的关系,以及系统初始相位的稳定性及降水资料的一致性。分析结果表明,在常规参量的基础上添加偏振参量并采用模糊逻辑法构建的综合识别模式和常规识别模式都能较好地识别地物,但综合识别模式明显改善了常规识别模式0速度区过度识别的问题,且在地物与降水回波混合的情况下叠加混合回波识别模式具有更加明显的优势。雷达改造前,ZDR及ρHV（0）在信噪比小于25 dB时受噪声影响很大,测量值存在较大误差,资料变得不可信;通过这次的升级改造,其信噪比探测阈值由25 dB降低到15 dB。系统初始相位比改造前更加稳定,随仰角和时间的波动性更小。利用垂直扫描数据进行系统误差订正后的ZDR资料能较好地反映降水粒子的实际情况,ZDR随信噪比的变化较之改造前更加平稳,而对差传播相移ΦDP进行分类处理后拟合的差传播相移率KDP资料也与实际情况一致。 相似文献
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广州S波段双偏振雷达数据质量初步分析 总被引：4，自引：5，他引：4
广东省已经通过新布设或对CINRAD\SA雷达的升级改造完成5部S波段双偏振雷达的业务运行。受目前双偏振雷达技术水平限制,双偏振雷达偏振量很不稳定,因此偏振雷达资料使用前需要对数据可用性、偏振量的系统偏差等进行初步分析,以保证偏振雷达后续产品的可靠性。使用广州S波段双偏振雷达稳定运行后的2016年7—8月连续观测资料,分析了噪声对零滞后相关系数ρHV(0)及差分反射率因子ZDR的影响和订正效果。结果表明:当SNR小于20.0 dB时,偏振参量ρHV(0)和ZDR的稳定性变差,数据不可用;噪声订正后,数据可用的SNR阈值减小为17.0 dB。进一步分析了经过噪声订正后的ZDR和ZH之间的关系,并与雨滴谱反演结果及理论值进行对比。结果表明:广州雷达ZDR较雨滴谱反演值和理论值均偏小,ZDR观测值存在系统偏差。结合广州的气候特征,对偏振量系统误差估计的微雨滴法的指数进行了调整,基于此方法分析了ZDR、初始相位ΦDP (0)的系统误差随方位角的变化。结果表明:ZDR系统误差随方位角在-0.29~0.22 dB之间波动,剔除遮挡后的平均偏差为-0.09 dB,与实测ZDR值和雨滴谱反演值及理论值对比偏小的结论一致,但偏差大小有区别;同时,ΦDP (0)随方位角有4 °左右的波动。分析还发现ZDR、ΦDP (0)系统误差有随时间波动的特征。最后挑选个例对ZDR进行噪声和系统误差订正后发现,订正后的ZDR得到改善。这些初步分析和结果对S波段双偏振雷达数据的使用有一定的参考意义。 相似文献
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基于Rayleigh-Gans散射原理构造一个S波段双线偏振雷达模拟器。模拟器考虑了云冰、雪、雨和雹4种水凝物,以水凝物的混合比和数浓度以及水凝物粒子的轴比、相对介电常数、下落倾角为输入量,计算得到水平/垂直偏振反射率因子、差分反射率、比差分相位等偏振量。通过二维理想飑线模拟的试验结果表明,模拟器合理地再现了二维理想飑线系统成熟期的主要偏振特征:雹的反射率较高,差分反射率较低(又称Zdr洞);对流云区的Zdr柱;层云区的反射率和比差分相位的0℃层亮带特征;雨滴反射率与差分反射率因子的“雨线”统计特征。利用该模拟器建立了模式变量和偏振雷达观测的联系,有助于未来将偏振雷达观测资料应用于模式预报效果评估及对流尺度资料同化等方面的研究和应用。 相似文献
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天气雷达可为中尺度对流系统研究提供高时空分辨率资料, 但降雨衰减和地形遮挡等因子会对雷达信号产生严重影响。针对广东省韶关市新丰县C波段双偏振天气雷达, 选取了2018年6月8日台风“艾云尼”、8月30日华南季风降水和9月16日台风“山竹”三次降雨过程, 采用基于差分相位(ΦDP)数据的扩展自适应降雨廓线算法对雷达反射率因子(ZH)数据进行了降雨衰减和部分地形遮挡衰减订正研究, 并将订正结果与广州S波段双偏振天气雷达探测结果进行了直接对比检验, 与中国气象局龙门云物理野外科学试验基地的4台二维视频雨滴谱仪(2D Video Distrometer, 2DVD)实测雨滴谱数据反演的雷达仿真探测量及国内外ZH-KDP经验统计公式进行了间接对比检验, 获得较好结果。最后选择具体降雨个例, 订正结果清晰展现了台风螺旋雨带中对流单体雷达回波强度从地面到高空的垂直结构特征, 提高了复杂地形区域雷达对极端天气的近地面探测能力。 相似文献
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与常规雷达相比,双线偏振天气雷达在降水系统的准确探测、资料质量的提高等方面具有明显的优势,但X波段双线偏振雷达资料受衰减和地物的影响较大,需要进行必要的衰减和地物订正。本文以2010年7月中国气象局在广东阳江开展的遥感数据比对试验得到数据为例,用ZH和ZDR结合的方法对ZH进行衰减订正,用ZH和ZDR的方差识别地物回波,并利用反射率因子垂直廓线订正受地物影响的底层回波。将订正后的ZH与S波段雷达探测的ZH相比较,将订正后的ZH与KDP的散点图和拟合的KDP与ZH曲线关系对比验证。结果表明经过订正的ZH与S波段雷达探测的ZH一致性较好,与拟合曲线也更为吻合,说明方法能有效提高雷达资料的质量。 相似文献
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X 波段双极化雷达对云中水凝物粒子的相态识别 总被引：7，自引：1，他引：6
人工影响天气研究需对云中降水粒子的相态和分布结构进行准确识别,以便提高人工影响天气作业效率.中国科学院大气物理研究所的车载X波段双极化雷达可提供与云中降水粒子大小、形状、相态等特征密切相关的4个极化参数:反射率因子、差分反射率、差分相移率、水平和垂直极化相关系数.利用这4个极化参数加上环境温度作为5个输入参量,建立了降水粒子相态模糊逻辑识别算法,识别的降水粒子有10种:毛毛雨、雨、湿霰、干霰、小雹、大雹、雨加雹、湿雪、干雪、冰晶.利用此雷达的实际观测资料,并与地面和飞机空中实测资料对照,对我国南、北方地区观测的降水天气过程进行分析,结果表明:建立的模糊逻辑算法对云内水凝物粒子的相态识别分类合理. 相似文献
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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 (ZH), radial velocity (V), differential reflectivity (ZDR), and specific differential phase (KDP). The results showed that: (1) DP-PAWR has better ability to detect mesoscale weather systems than CINRAD/SA-D; 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 ZH and V structures are acceptable, while its sensitivity is worse than that of CINRAD/SA-D. The ZH suffers from attenuation and the ZH area distribution is distorted around strong rainfall regions. (3) DP-PAWR’s ZDR is close to a normal distribution but slightly smaller than that of CINRAD/SA-D. The KDP 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. 相似文献
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为研究梅雨期极端对流系统的微物理特征,利用2013—2014年江淮梅雨期间南京溧水S波段双偏振雷达探测资料和地面自动站小时降水资料,统计分析了两类极端对流降水系统的微物理特征及差异。这两类极端对流系统的定义基于地面降水强度和雷达回波顶高,分别为所有对流中降水强度最强的1%（R类:小时降水强度>46.2 mm/h）和对流发展高度最高的1%（H类:20 dBz回波顶高>14.5 km）。结果显示这两类极端对流系统仅有30%的样本重合,显示了二者之间的弱相关性。对于相同的反射率因子ZH,R类极端对流系统的近地面差分反射率因子ZDR通常较H类极端对流小约0.2 dB,表明R类极端对流具有较小的平均粒径。结合双偏振雷达反演的粒子大小和相态分布显示,虽然两类极端对流都表现出海洋性对流降水特征,但R类极端对流较H类极端对流的总体雨滴粒径更小而数浓度更高,导致R类极端对流系统的地面降水更强。与R类极端对流系统相比,H类极端对流系统的上升运动更强,将更多的水汽和过冷水输送到0℃层以上,有利于形成更大的冰相粒子（如霰粒子等）,并通过融化形成大雨滴。以上研究表明,梅雨期降水强度和对流发展深度并没有必然的联系,极端降水主要是中等高度的对流引起。 相似文献
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A major issue in radar quantitative precipitation estimation is the contamination of radar echoes by non-meteorological targets such as ground clutter, chaff, clear air echoes etc. In this study, a fuzzy logic algorithm for the identification of non-meteorological echoes is developed using optimized membership functions and weights for the dual-polarization radar located at Mount Sobaek. For selected precipitation and non-meteorological events, the characteristics of the precipitation and non-meteorological echo are derived by the probability density functions of five fuzzy parameters as functions of reflectivity values. The membership functions and weights are then determined by these density functions. Finally, the non-meteorological echoes are identified by combining the membership functions and weights. The performance is qualitatively evaluated by long-term rain accumulation. The detection accuracy of the fuzzy logic algorithm is calculated using the probability of detection (POD), false alarm rate (FAR), and clutter-signal ratio (CSR). In addition, the issues in using filtered dual-polarization data are alleviated. 相似文献
17.
To analyze the effects of gas cannons on clouds and precipitation, multisource observational data, including those from National Centers for Environmental Prediction (NCEP) reanalysis, Hangzhou and Huzhou new-generation weather radars, laser disdrometer, ground-based automatic weather station, wind profiler radar, and Lin''an C-band dual polarization radar, were adopted in this study. Based on the variational dual-Doppler wind retrieval method and the polarimetric variables obtained by the dual-polarization radar, we analyzed the microphysical processes and the variations in the macro - and microphysical quantities in clouds from the perspective of the synoptic background before precipitation enhancement, the polarization echo characteristics before, during and after enhancement, and the evolution of the fine three-dimensional kinematic structure and the microphysical structure. The results show that the precipitation enhancement operation promoted the development of radar echoes and prolonged their duration, and both the horizontal and vertical wind speeds increased. The dual-polarization radar echo showed that the diameter of the precipitation particles increased, and the concentration of raindrops increased after precipitation enhancement. The raindrops were lifted to a height corresponding to 0 to -20 ℃ due to vertical updrafts. Based on the disdrometer data during precipitation enhancement, the concentration of small raindrops (lgNw) showed a significant increase, and the mass-weighted diameter Dm value decreased, indicating that the precipitation enhancement operation played a certain“lubricating”effect. After the precipitation enhancement, the concentration of raindrops did not change much compared with that during the enhancement process, while the Dm increased, corresponding to an increase in rain intensity. The results suggest the positive effect of gas cannons on precipitation enhancement. 相似文献
18.
Using China New Generation Weather Radar (CINRAD) level-II data, the original algorithms for removing isolated non-meteorological echoes and ground clutters in radar data, which have been applied to Weather Surveillance Radar-1988 Doppler (WSR-88D) in the USA and Severe Weather Automatic Nowcast (SWAN) system in China, are modified and improved. To remove isolated non-meteorological echoes, the new algorithm introduces a constraint parameter (Po) to distinguish whether a window of 5 × 5 points is isolated as external echoes. A statistical analysis of 150 radar scans (5 cases, with each case comprising 30 scans) under three different echo types (small-scale convection, typhoon, and large-scale synoptic system) shows that the constraint parameter Po ? 0.167 is suitable for removing isolated non-meteorological echoes while preserving the edge of meteorological echoes. A new parameter, NDZ, which promotes the ability of the algorithm to identify the ground clutters appearing at two adjacent elevation angles, is constructed based on the vertical continuity of reflectivity. These improved algorithms are tested for four cases (three cases of isolated non-meteorological echoes and one case of ground clutters). Based on the statistics of 232 volume scans of radar data (on a temporal resolution of 1 h) measured at Nanchang station from 0000 UTC 5 to 1600 UTC 14 March 2015, it is found that the improved algorithms not only eliminate most (over 95% under clear-sky conditions) of the isolated non-meteorological echoes and ground clutters (including those appearing at two adjacent elevation angles), but also well preserve the structure of meteorological echoes (storms). Key words: radar, isolated non-meteorological echoes, ground clutter, quality control 相似文献
19.
The exact quantitative estimation of hailstorm precipitation intensity, allowing determining successfully the crop hail damage, is extremely necessary while carrying out of programs of experimental researches of the hail clouds as well as at realization of operative projects on hail suppression. On the other hand, the possibility of obtaining a trustworthy information about changes of hailfall intensity during cloud seeding operations enables to judge more objectively about seeding effect and to make a decision about its beginning and termination. Just because of such a parameter, the kinetic energy of hailfalls presents a great interest for the researchers. As it is known, measuring the kinetic energy of hailfalls is carried out both directly by ground network of hailpads, and by radar methods. The accuracy of the radar methods of the hail kinetic energy measurement strongly depends not only on the choice of an optimum formula for calculation but also on the algorithm used for separating hail and rain parts of radar echo and on the way it was used in the hail–rain mixture zone of precipitation.The method of calculating the kinetic energy of the hailfalls, based on empirical dependence of hail probability Ph on a height of a zone of a radar echo with a reflectivity of 45 dBZ above a level of zero isotherm ΔH45, is offered in the given work. The algorithm of separating hail and rain parts of a radar echo and the way it was applied in a hail–rain mixture zone is described. The examples of hail streaks in contours of radar reflectivity and in isopleths of hail kinetic energy obtained using the given algorithm are shown.In Mendoza province (Argentina), a hail suppression project (1993–1997) for the analysis of the vertical structure of a radar echo with Zmax > 45 dBZ, such new parameter is an integral altitude, was used. This dimensionless parameter is most sensitive to such a condition of radar echo when all four contours of increased reflectivity Z45, Z55, Z65, and Z75 synchronously reach the maximal values. The analysis of time distributions of the main radar parameters of hailstorms on a background of values of integral altitude is resulted. It is shown that local hailfall maximum intensities on the ground are observed after the achievement of maximum integral altitude with a certain delay. It enables to predict zones of the greatest hail damage in a mode of radar observation. 相似文献