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在Ka波段云雷达上升级改造建成的Ka/Ku（Ka和Ku波段波长分别为8.9 mm和2.2 cm）双波段云雷达2019年用于华南云降水垂直结构观测,以改进云内动力和微物理参数探测能力。为了利用该双波段云雷达研究华南降水微物理和动力结构,本文提出了基于双波段云雷达回波强度谱密度（SZ）数据和最优估计技术的云内空气垂直运动速度（Vair）、雨滴谱（DSD）、含水量（LWC）、雨强（R）的反演方法（DWSZ）,雨区衰减的订正方法。利用2019年在广东龙门观测的一次降水过程数据,对比分析了云雷达反演的微物理参数与雨滴谱直接观测量,并检验了云雷达反演的低层空气垂直运动速度,利用反演结果分析了一次混合云过程的Vair与这些微物理参数的垂直结构和相互关系。结果表明:Ka/Ku双波段云雷达合理反演了微降水微物理和动力参数及其垂直分布,经过衰减订正的Ka和Ku波段回波强度偏差明显减小。该双波段云雷达数据可以用于分析0～30 dBZ回波强度的云降水垂直结构。本次过程为混合云降水,对流单体前部存在明显的上升气流,后部存在下沉气流;从平均垂直结构来看:Vair和粒子平均直径（Dm）在2 km高度层到达最大,粒子数密度（Nw）、LWC和R在2 km以下明显增强,粒子直径却减小,水汽凝结过程、雨滴碰并云滴是本次过程的主要机制。这一工作验证了Ka和Ku波段组合的双波段云雷达的可行性,为Ka/Ku波段云雷达技术的推广,单波段云雷达反演算法进一步改进,云降水精细结构分析等提供了基础。 相似文献
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对基于雷达反射率因子观测数据的层状云降水粒子谱参数反演算法进行研究。（1）给出层状云降水粒子谱参数的反演理论和反演算法流程;（2）选取吉林省伊通县的一次降水层状云过程进行反演试验和验证分析,利用雷达反射率因子观测数据反演得到雨滴平均直径和数浓度参数,并用放置在伊通县气象局观测场中的Parsivel激光雨滴谱仪的实测数据与近地层反演结果进行对比。结果发现,通过反演算法计算得到的滴谱与实测滴谱的变化趋势基本相同,而且反演的雨滴平均直径和数浓度在量级和数值上的大小与实测数据具有良好的一致性,说明该反演方法用于从现有天气雷达回波强度数据中挖掘出降水性层状云的微物理参数是可行的。 相似文献
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利用多普勒雷达资料、FY-2E静止卫星和MODIS极轨卫星反演产品,研究2012年7月21日北京特大暴雨的云降水结构及云雨转化特征。结果表明:降水过程三阶段的云降水垂直结构不同。1)在暖区对流降水阶段,降水以暖雨机制启动,雨滴在暖区存在深厚的碰并增长过程,暖雨过程对降水起主要贡献。随着云体的发展,冷雨过程加剧。T-Re分析表明,-10℃层以下云滴凝结碰并显著,-10℃层以上为深厚的冰相增长带,云顶以冰相大粒子为主,云水向雨水转化迅速。2)在锋面对流降水阶段,降水系统为高度组织化的"低质心"强降水液态MCC(Mesoscale Convective Complex)系统。回波强度在冰水混合层增长较快,冻结层是此阶段成雨微物理的关键层。降水粒子在暖云区碰并增长较快,而蒸发或破碎过程并不显著。3)在锋后降水阶段,0℃层附近冰晶粒子与云水的碰并增长较为明显。前期降水存在明显的雨滴蒸发过程。随着云体的发展,暖区云水含量较少,降水粒子不能有效碰并增长。 相似文献
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切变线降水系统微物理特征及隆水机制个例分析 总被引：2，自引：0，他引：2
利用机载云粒子探测系统(PMS).对2004年7月1日影响吉林省的一次切变线降水过程进行了探测飞行,利用所获取的宏微观资料对此次降水过程的微物理结构、降水机制进行综合分析.结果表明:此次切变线降水云系主要由高层云、雨层云、碎云构成,高层云和雨层云中间夹有1100m左右的无云区;3类云中平均云滴浓度、平均云滴直径各不相同;云水含量随高度分布不均匀,云的不同部位云水含量起伏较大;冰晶浓度平均为17.3个/L;此次探测的降水云系符合Bergeron提出的催化云一供水云相互作用导致降水的概念.根据云图及其他探测资料综合分析,冰晶主要产生于高层云上部或卷层云的冰晶播撒,供水云为高层云中下部和雨层云. 相似文献
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雷达反射率因子在中尺度云分辨模式初始化中的应用Ⅰ：云微物理量和垂直速度的反演 总被引：2，自引：1，他引：2
对于水平网格距小于10 km的高分辨率非静力平衡的显式云分辨模式,云微物理量的初始化以及物理量之间的相互协调是十分重要的,并且一直是云分析领域的一个难题。考虑在云雨处于定常状态的前提下,根据暖云过程,可得到云中水成物之间相互转化以及与垂直速度的约束关系,而雨水含量跟雷达反射率因子(Z)有关。因此,采用合肥新一代天气雷达2003年7月5日02时(北京时)的观测资料,针对雷达探测的特点对雷达原始数据进行了坐标转换,并进行了插值处理和简单的质量控制,然后依据Z-qr关系和定常暖云方案,反演了雨水混合比(qr)、云水混合比(qc)、水汽混合比(qv)和垂直速度(w)。结果表明,由此得到的雷达回波主要特征及量值分布与雷达站的CAPPI图像基本一致;水汽、云水、雨水和垂直速度量值大小的分布与雷达回波强度的分布也是吻合的,体现出了云中水成物和垂直速度的三维分布结构;各物理量的量值也符合梅雨锋暴雨的特点,梅雨锋积层混合云系中层状云和对流云的差别十分明显。在较强的回波区,雨水在6 km以下含量较大,最大值位于4 km左右,可超过3.0 g/kg;上升速度在5 km左右最大,最大值超过5 m/s;云水含量大值区位于5 km以上,在7 km高度上达到最大,超过3.0 g/kg;雨滴末速度虽然上下比较一致,一般几米每秒,但在5 km左右为大值区。 相似文献
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利用极化雷达分析层状云中水凝物粒子性状分布 总被引：11，自引：1，他引：10
使用中国科学院大气物理研究所的X波段双线极化雷达系统探测资料, 讨论了双极化雷达各种观测参量所反映的水凝物粒子的物理本质。提出了对存在融化层的层状云使用雷达探测变量确定零度层高度以及结合地面温度反演温度廓线的方法。在存在融化层的层状云中, 对雷达探测资料在层状云降水期间的RHI资料进行分层统计, 结合国际上已有的研究结果, 获得了几种主要水凝物粒子的极化雷达参数 (即反射率、 差分反射率、 单位差分传播相移、 相关系数) 范围; 在此基础上使用模糊逻辑方法, 对水凝物粒子进行分类, 分类结果反映了层状云的相态结构分布特点。最后, 根据两个实例, 使用反射率、 差分反射率衰减订正后的数据, 结合层状云的基本特点, 分析了层状云的垂直结构和粒子的相态结构以及层状云中可能的降水机制, 并使用反演的粒子分布结构代替雷达反射率因子结构对降水微物理过程进行了讨论, 结果验证了顾震潮 (1980) 在20世纪60年代提出的层状云降水的三层概念模型。本文结果为使用双极化雷达研究云降水机制提供了方法, 表明双极化雷达在云降水物理的研究中具有广阔的应用前景。 相似文献
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雷达反射率因子在中尺度云分辨模式初始化中的应用Ⅱ：数值模拟试验 总被引：3，自引：1，他引：3
将反演的云微物理量和垂直速度采用"牛顿连续松弛逼近"(Nudging)技术应用到GRAPES模式中,对一次梅雨锋暴雨过程进行了数值模拟。通过设计不同的试验方案,分别对水汽、液态水和垂直速度对Nudging效果以及预报结果的影响进行了考察。研究发现,采用Nudging初始化方法,可使背景场与观测反演资料相协调,实现了模式中对流的热启动,模式预报的开始时刻就产生降水,缩短Spin-up时间。水汽对降水至关重要,对降水的强度和持续时间都有重要影响;云水、雨水和垂直速度决定了初始时刻对流的强弱分布并产生降水;水平风场决定了系统的移动方向,对预报降水的落区有重要影响。模式比较成功地模拟了6 h的降水过程,中尺度天气系统的时空特征比较明显,对流中心上升速度最大值约2.0 m/s,云水含量400 hPa以上较大,最大值约1.5 g/kg,雨水含量500 hPa以下较大,最大约3.0 g/kg,底层辐合高层辐散。反演资料对降水的影响随预报时间的增加而减弱,预报1 h之内反演资料有明显影响,3 h之后的预报则主要依赖模式自身。鉴于仅使用一部雷达资料的反射率因子资料,雷达资料没有覆盖整个模式区域,天气系统被截断,反演和同化过程还采用了一些经验参数方法等原因,数值模拟结果与雷达观测之间还存在一定的差异,有待于更深入的研究。 相似文献
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2015年10月29日弱降雨前后的层状云微物理参数反演和分析 总被引：4，自引：4，他引：0
利用Ka波段毫米波云雷达和微波辐射计资料对2015年10月29日安徽寿县的一次弱降雨过程的云参数进行了反演,所采用的反演方案是单参数法和双参数法。论文先介绍了单参数和双参数反演方法,然后反演了降雨前后的云微物理参数,对比分析表明：（1）降水发生前云滴数浓度较大,典型值1 000个·cm-3左右,有效半径小于4.5 μm;（2）降雨后,云滴数浓度显著减小,典型值在500个·cm-3左右,但有效半径略增大了1~1.5 μm;（3）云中含水量的变化不明显,降雨后略增大,增加量在0.1 g·m-3以内; （4）降水发生前,云微物理参数随高度的起伏较大,降水后的廓线比较平缓,显示出降雨后的云层动力特性更稳定。 相似文献
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Application of Radar Reflectivity Factor in Initializing Cloud-Resolving Mesoscale Model. Part Ⅰ: Retrieval of Microphysical Elements and Vertical Velocity 
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下载免费PDF全文 Assuming that cloud reaches static state in the warm microphysical processes, water vapor mixing ratio(qv), cloud water mixing ratio (qc), and vertical velocity (w) can be calculated from rain water mixing ratio (qr)- Through relation of Z-qr, qr can be retrieved by radar reflectivity factor (Z). Retrieval results indicate that the distributions of mixing ratios of vapor, cloud, rain, and vertical velocity are consistent with radar images, and the three-dimensional spatial structure of the convective cloud is presented. Treating q,v saturated at the echo area, the retrieved qr is about 0.1 g kg-1, qc is always less than 0.3 g kg-1, w is usually below 0.5 m s-1, and rain droplet terminal velocity (vr) is around 5.0 m s-1 in the place where radar reflectivity factor is about 25 dBz; in the place where echo is 45 dBz, the retrieved qr and qc are always about 3.0 g kg-1, w is greater than 5.0 m s-1, and vr is around 7.0 m s-1. In the vertical, the maximum updraft velocity is greater than 3.0 m s-1 at the height of around 5.0 kin, the maximum cloud water content is about 3.0 g kg-1 above 5 km and the maximum rain water content is about 3.0 g kg-1 below 6 kin. Due to the assumption that the cloud is in static state, there will be some errors in the retrieved variables within the clouds which axe rapidly growing or dying-out, and in such cases, more sophisticated radar data control technique will help to improve the retrieval results. 相似文献
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为了发展云雷达与微波辐射计联合反演液态水含量的方法, 利用2019年4—9月中国气象科学研究院在广东龙门开展的综合观测试验中的双波段云雷达和微波辐射计数据, 首先检验了在降水条件下微波辐射计天顶观测和斜路径观测两种探测模式反演温度(T)、相对湿度(RH)、液态水含量(LWC)和液态水路径(LWP)的合理性, 然后分析了两种探测设备反演LWC和LWP的差别。得到以下结论: (1)微波辐射计在斜路径观测模式下反演的产品受降水影响较小, 其反演结果明显优于天顶观测模式; (2)两种探测设备反演的LWP相关性较好且随时间变化较为一致, 但云雷达反演LWP与平均回波强度有明显相关, 随着雷达回波强度的增大, 云雷达与微波辐射计反演的LWP之比越大; (3)两种探测设备反演的LWC相关性较差且存在明显偏差, 在不考虑融化层的情况下单波段云雷达反演LWC与微波辐射计随高度变化趋势相近, 双波段云雷达反演LWC与微波辐射计反演结果在1 km及其以上区间存在明显差异。 相似文献
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Cloud properties were investigated based on aircraft and cloud radar co-observation conducted at Yitong, Jilin, Northeast China. The aircraft provided in situ measurements of cloud droplet size distribution, while the millimeter-wavelength cloud radar vertically scanned the same cloud that the aircraft penetrated. The reflectivity factor calculated from aircraft measurements was compared in detail with simultaneous radar observations. The results showed that the two reflectivities were comparable in warm clouds, but in ice cloud there were more differences, which were probably associated with the occurrence of liquid water. The acceptable agreement between reflectivities obtained in water cloud confirmed that it is feasible to derive cloud properties by using aircraft data, and hence for cloud radar to remotely sense cloud properties. Based on the dataset collected in warm clouds, the threshold of reflectivity to diagnose drizzle and cloud particles was studied by analyses of the probability distribution function of reflectivity from cloud particles and drizzle drops. The relationship between reflectivity factor (Z) and cloud liquid water content (LWC) was also derived from data on both cloud particles and drizzle. In comparison with cloud droplets, the relationship for drizzle was blurred by many scatter points and thus was less evident. However, these scatters could be partly removed by filtering out the drop size distribution with a large ratio of reflectivity and large extinction coefficient but small effective radius. Empirical relationships of Z-LWC for both cloud particles and drizzle could then be derived. 相似文献
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Cloud microphysical properties including liquid and ice particle number concentration (NC), liquid water content (LWC), ice water content (IWC) and effective radius (RE) were retrieved from CloudSat data for a weakly convective and a widespread stratus cloud. Within the mixed-phase cloud layers, liquid-phase fractions needed to be assumed in the data retrieval process, and one existing linear (p1) and two exponential (p2 and p3) functions, which estimate the liquid-phase fraction as a function of subfreezing temperature (from -20°C to 0°C), were tested. The retrieved NC, LWC, IWC and RE using p1 were on average larger than airplane measurements in the same cloud layer. Function p2 performed better than p1 or p3 in retrieving the NCs of cloud droplets in the convective cloud, while function p1 performed better in the stratus cloud. Function p3 performed better in LWC estimation in both convective and stratus clouds. The REs of cloud droplets calculated using the retrieved cloud droplet NC and LWC were closer to the values of in situ observations than those retrieved directly using the p1 function. The retrieved NCs of ice particles in both convective and stratus clouds, on the assumption of liquid-phase fraction during the retrieval of liquid droplet NCs, were closer to those of airplane observations than on the assumption of function p1. 相似文献
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Radar parameters including radar reflectivity,Doppler velocity,and Doppler spectrum width were obtained from Doppler spectrum moments.The Doppler spectrum moment is the convolution of both the particle spectrum and the mean air vertical motion.Unlike strong precipitation,the motion of particles in cirrus clouds is quite close to the air motion around them.In this study,a method of Doppler moments was developed and used to retrieve cirrus cloud microphysical properties such as the mean air vertical velocity,mass-weighted diameter,effective particle size,and ice content.Ice content values were retrieved using both the Doppler spectrum method and classic Z-IWC(radar reflectivity-ice water content) relationships;however,the former is a more reasonable method. 相似文献
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通过分析W波段和Ka波段云雷达同时探测回波的差异,验证了W波段云雷达初样机的探测性能。结果表明：1）W波段云雷达初样机工作稳定,两个波段雷达都可以探测云层、云的边界、云厚等宏观参数,也可以反映出云的精细结构及云内微物理参数的变化,回波强、速度小、谱宽大的冰晶云含有上升气流及较多过冷水。2）增强模式的W波段云雷达在近地面探测雾、霾的能力比Ka波段云雷达强;两部云雷达对云层较薄的云探测能力基本相当,对多层云、云层较厚、含水量较多的云及降水的探测,由于强衰减的作用,W波段雷达所测云厚度小、云顶低、回波强度小,并且非瑞利散射也会造成W波段雷达的回波强度降低。 相似文献
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The First Observed Cloud Echoes and Microphysical Parameter Retrievals by China''s 94-GHz Cloud Radar 总被引：1，自引：0，他引：1 下载免费PDF全文
下载免费PDF全文 WU Juxiu WEI Ming HANG Xin ZHOU Jie ZHANG Peichang LI Nan 《Acta Meteorologica Sinica》2014,28(3):430-443
By using the cloud echoes first successfully observed by China's indigenous 94-GHz SKY cloud radar, the macrostructure and microphysical properties of drizzling stratocumulus clouds in Anhui Province on 8 June2013 are analyzed, and the detection capability of this cloud radar is discussed. The results are as follows.(1) The cloud radar is able to observe the time-varying macroscopic and microphysical parameters of clouds,and it can reveal the microscopic structure and small-scale changes of clouds.(2) The velocity spectral width of cloud droplets is small, but the spectral width of the cloud containing both cloud droplets and drizzle is large. When the spectral width is more than 0.4 m s-1, the radar reflectivity factor is larger(over –10 dBZ).(3) The radar's sensitivity is comparatively higher because the minimum radar reflectivity factor is about–35 dBZ in this experiment, which exceeds the threshold for detecting the linear depolarized ratio(LDR) of stratocumulus(commonly –11 to –14 dBZ; decreases with increasing turbulence).(4) After distinguishing of cloud droplets from drizzle, cloud liquid water content and particle effective radius are retrieved. The liquid water content of drizzle is lower than that of cloud droplets at the same radar reflectivity factor. 相似文献
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Knowledge of cloud properties and their vertical structure is important for meteorological studies due to their impact on both the Earth’s radiation budget and adiabatic heating within the atmosphere. The objective of this study is to evaluate bulk cloud properties and vertical distribution simulated by the US National Oceanic and Atmospheric Administration National Centers for Environmental Prediction Global Forecast System (GFS) using three global satellite products. Cloud variables evaluated include the occurrence and fraction of clouds in up to three layers, cloud optical depth, liquid water path, and ice water path. Cloud vertical structure data are retrieved from both active (CloudSat/CALIPSO) and passive sensors and are subsequently compared with GFS model results. In general, the GFS model captures the spatial patterns of hydrometeors reasonably well and follows the general features seen in satellite measurements, but large discrepancies exist in low-level cloud properties. More boundary layer clouds over the interior continents were generated by the GFS model whereas satellite retrievals showed more low-level clouds over oceans. Although the frequencies of global multi-layer clouds from observations are similar to those from the model, latitudinal variations show discrepancies in terms of structure and pattern. The modeled cloud optical depth over storm track region and subtropical region is less than that from the passive sensor and is overestimated for deep convective clouds. The distributions of ice water path (IWP) agree better with satellite observations than do liquid water path (LWP) distributions. Discrepancies in LWP/IWP distributions between observations and the model are attributed to differences in cloud water mixing ratio and mean relative humidity fields, which are major control variables determining the formation of clouds. 相似文献
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利用我国自己研制的W波段云雷达地基探测资料,分析了合肥一次小雨云系的微物理过程,然后利用两个不同地区的地基及机载探测资料,初步反演了水云及卷云的微物理参数。结果表明:(1)回波强度增大,多普勒速度、线性退极化比(LDR)、谱宽激增的地方为融化层顶,根据LDR亮带可初步判定融化层的厚度;(2)利用经验关系法,对卷云冰水含量和水云的液态水含量进行了反演,利用推导的公式反演得到冰晶云云粒子的有效半径;(3)利用逐库订正法对水云的回波强度进行订正,得到了衰减订正后的液态水含量,减小了反演误差。 相似文献