Turbulence and Rainfall Microphysical Parameters Retrieval and Their Relationship Analysis Based on Wind Profiler Radar Data

Rainfall is triggered and mainly dominated by atmospheric thermo-dynamics and rich water vapor.Nonetheless, turbulence is also considered as an important factor influencing the evolution of rainfall microphysical parameters. To study such an influence, the present study utilized boundary layer wind profiler radar measurements. The separation point of the radar power spectral density data was carefully selected to classify rainfall and turbulence signals;the turbulent dissipation rate ε and rainfall microphysical parameters can be retrieved to analyze the relationship betweenε and microphysical parameters. According to the retrievals of two rainfall periods in Beijing 2016, it was observed that(1) ε in the precipitation area ranged from 10^(-3.5) to 10^(-1) m^(2) s^(-3) and was positively correlated with the falling velocity spectrum width;(2) interactions between turbulence and raindrops showed that small raindrops got enlarge through collision and coalescence in weak turbulence, but large raindrops broke up into small drops under strong turbulence, and the separation value of ε being weak or strong varied with rainfall attributes;(3) the variation of rainfall microphysical parameters(characteristic diameters, number concentration, rainfall intensity, and water content) in the middle stage were stronger than those in the early and the later stages of rainfall event;(4) unlike the obvious impacts on raindrop size and number concentration, turbulence impacts on rain rate and LWC were not significant because turbulence did not cause too much water vapor and heat exchange.

Application of wind profiler data to rainfall analyses in Tazhong Oilfield region,Xinjiang,China

To improve the level of meteorological service for the Oilfield region in the Taklimakan Desert, the Urumqi Institute of Desert Meteorology of the China Meteorological Administration （CMA） conducted a detection experiment by means of wind profiling radar （WPR） in Tazhong Oilfield region of Xinjiang, China in July 2010. By using the wind profiler data obtained during the rainfall process on 27 July, this paper analyzed the wind field fea- tures and some related scientific issues of this weather event. The results indicated that： （1） wind profiler data had high temporal resolution and vertical spatial resolution, and could be used to analyze detailed vertical structures of rainfall processes and the characteristics of meso-scale systems. Before and after the rain event on 27 July, the wind field showed multi-layer vertical structures, having an obvious meso-scale wind shear line and three airflows from different directions, speeding up the motion of updraft convergence in the lower atmosphere. Besides, the wind directions before and after the rainfall changed inversely with increasing height. Before the rain, the winds blew clockwise, but after the onset of the rain, the wind directions became counterclockwise mainly; （2） the temperature advection derived from wind profiler data can reproduce the characteristics of low-level thermodynamic evolution in the process of rainfall, which is capable to reflect the variation trend of hydrostatic stability in the atmosphere. In the early stage of the precipitation on 27 July, the lower atmosphere was mainly affected by warm advection which had accumulated unstable energy for the rainfall event and was beneficial for the occurrence of updraft motion and precipitation; （3） the ＂large-value zone＂ of the radar reflectivity factor Z was virtually consistent with the onset and end of the rainfall, the height for the formation of rain cloud particles, and precipitation intensity. The reflectivity factor Z during this event varied approximately in the range of 18-38 dBZ and the rain droplets formed mainly at the layer of 3,800-4,500 m.

Detecting sand-dust storms using a wind-profiling radar

Sand-dust storm is a type of disastrous weather, typically occurring in arid and semi-arid climates. This study selected a region in the hinterlands of the Taklimakan Desert, called the Tazhong region, as the experimental area to quantitatively estimate the particle concentrations of sand-dust storms using the boundary layer wind-profiling radar. We thoroughly studied the radar echo signals and reflectivity factor features during the sand-dust storms. The results indicate that（1） under sand-dust storm conditions, boundary layer wind-profiling radar cannot capture the complete information regarding horizontal wind velocity and direction, but it can obtain the backscattering intensity of sand-dust storms; and（2） during sand-dust storms particle size distributions in the surface layer closely resemble log-normal distributions, with sand-dust particles sizes of 90–100 μm accounting for the maximum particle probability. Retrieved particle size distributions at heights of 600, 800, and 1000 m follow log-normal distributions, and the expected value of particle diameter decreases gradually with increasing height. From the perspective of orders of magnitude, the retrieved results for particle number concentrations and mass concentrations are consistent with previous aircraft-detected results, indicating that it is basically feasible to use boundary layer wind-profiling radar to quantitatively detect the particle concentrations of dust storms.

Intermittent Clutter Removal Approach for Wind Profiler Data Based on Fractional Fourier Transform

Through the analysis of the target characteristics and according to the intermittent clutter bursting and short duration characteristics,a new method for the clutter recognition based on the fractional Fourier transform（FRFT）is proposed.This method is predicated on the fact that the FRFT perfectly localizes a chirp signal as an impulse when the angle parameter of the transform matches the chirp rate of the chirp signal.The method involves detecting the presence of the intermittent clutter and correctly estimating its orientation in the time-frequency plane,removing the intermittent clutter in the fractional domain,and completing wind estimation by the power spectrum.By testing the artificial WPR-like signal and data measured from the field,we verify that the FRFT-based method is very effective.

THE INFLUENCE OF INHOMOGENEOUS WIND DISTRIBUTION ON DATA QUALITY FOR WIND PROFILING RADAR

Horizontal wind measured by wind profiling radar(WPR) is based on uniform wind assumption in volume of lateral beam. However, this assumption cannot completely meet in the real atmosphere. The subject of this work is to analyze the influence of atmospheric inhomogeneities for wind measurement. Five-beam WPR can measure two groups of horizontal wind components U and V independently, using the difference of horizontal wind components U and V can evaluate the influence of the inhomogeneity of the atmospheric motion on wind measurement. The influences can be divided into both inhomogeneous distribution of horizontal motion and vertical motion. Based on wind measurements and meteorological background information, a new means of coordinate rotation the two kinds of inhomogeneous factor was separated, and the impact in different weather background was discussed. From analysis of the wind measured by type of PB-II WPR(445MHz) during 2012 at Yanqing of Beijing, it is shown that the inhomogeneity of horizontal motion is nearly the same in U and V direction. Both the inhomogeneities of horizontal motion and vertical motion have influence on wind measurement, and the degrees of both influences are associated with changes of wind speed. In clear air, inhomogeneity of horizontal motion is the main influence on wind measurement because of small vertical velocity.In precipitation, the two influences are larger than that in clear air.

Wind Measurement with a Wind Profiling Radar

The first troposphere wind profiling radar in China has been in operation. The paper describes the radar parameters and characteristics with some experimental results presented.

Comparative Analysis on Physical Quantity Diagnosis and Wind Profile Radar Data of Two Heavy Rainfalls

[ Objective] The research aimed to contrast physical quantity diagnosis and wind profile radar data of two heavy rainfalls. [ Method ] From circulation background, physical quantity field and wind profile radar data, we analyzed two big rainstorm weather processes （8 -9 July and August 10） in Lianyungang City in 2012. [ Result] Rainstorm generation was related to favorable large-scale circulation situation. The first-stage precipitation during 8 -9 July was warm-zone precipitation, and the precipitation at the second stage was triggered by shear line. Precipitation on August 10 was generated by typhoon low-pressure inverted trough and cold air. Sufficient water vapor content and strong water vapor transportation were favorable for generation of the heavy precipitation. Suction effect by divergence at high layer and convergence at middle and low layers was favorable for maintenance of the strong ascending motion. Occurrence of the heavy precipitation must have ascending motion condition. But it was not that the stronger the ascending motion, the stronger the rainfall intensity. Kindex and θse500 -θse 850 were closely related to rainstorm occurrence. Horizontal wind data of the wind profile radar provided fine structure of the atmospheric horizontal motion at vertical direction, could clearly display vertical structure of the wind field in rainstorm process, and directly reflected change characteristics of the wind field in precipitation process. [ Conclusion] The research could provide reference for future forecast work.

超强台风“莫兰蒂”(1614)边界层结构的风廓线雷达观测分析

利用翔安风廓线雷达和厦门探空雷达资料,对2016年超强台风“莫兰蒂”外雨带(距离台风中心120~220 km)和外围晴空(距离台风中心400~630 km)边界层结构进行观测分析,结果表明:在超强台风“莫兰蒂”外雨带,风廓线雷达反演的最大切向风速高度分布在入流层下方0.5~1.0 km处,并且随着台风中心的靠近,最大切向风速和入流层高度都有降低的趋势,受降雨粒子的影响,风廓线雷达只能定性反映台风外雨带最大切向风速高度和入流层高度分布特征。在超强台风“莫兰蒂”外围晴空天气下,最大切向风速高度与入流层高度具有一致性,其边界层高度变化比较平稳,高度分布在1.2~1.6 km之间,能够定量反映台风外围晴空边界层高度分布;相对于传统热力驱动的湍流,台风系统边界层湍流主要由风切变驱动,台风外围湍流活动的增强主要发生在最大切向风速高度附近,除了风切变还有其他比较重要的驱动源,表明在台风边界层顶部附近有更加复杂的湍流活动,需要更加精细的湍流通量试验确定其来源。

STMAS同化风廓线雷达对台风“利奇马”融合实况风场的改进分析

为分析STMAS(space-time multiscale analysis system)同化风廓线雷达对三维风场的改进效果,本文以GRAPES-MESO、GRAPES-GFS 2种预报场作为背景场,对STMAS系统融合浙江省及周边一定范围的L波段边界层风廓线雷达数据,进行4组对比试验。通过试验结果与探空雷达实况数据和EC(european meteorological center)再分析资料的对比分析发现:(1)STMAS中融合越多的风廓线雷达信息,融合后的结果改变越明显;(2)从本文试验时段内各时次各层次试验数据与探空雷达差异的平均值来看,以GRAPES-GFS为背景场的融合效果相对较好;(3)通过与探空雷达对垂直风速的对比发现,接入风廓线雷达的STMAS风速场比未接入的STMAS风速更接近实况值,同时STMAS风速场比EC再分析资料更接近探空实况。

2022年“2.13”冀中大雪过程多源气象资料分析

利用常规观测资料、era5再分析资料、风廓线雷达产品、地基GPS/MET大气可降水量(precipitable water vapor,PWV)等,对2022年2月13日冀中大雪过程进行了详细分析。①降雪发生之前的36 h内PWV呈增长态势,0~12 h上升最快,12~36 h呈缓慢上升趋势。②降水量和PWV呈一定正相关关系,降雪期间PWV变化平稳,随着PWV出现连续下降,降水结束。③风廓线雷达的水平风向风速演变对降雪的预报有一定指示意义:3000 m突然出现20 m/s的西南低空急流,随着20 m/s的西南低空急流向下延伸至2500 m高度,降雪增强。④降雪之前,0.5 m/s及以上的正速度首先出现在1500 m以上,当2000 m以下突然出现1.0 m/s以上的正速度后,0~3 h内降雪发生。⑤1000 m以下垂直速度增加到1.5 m/s及以上时,降雪增强。⑥降雪期间C_(n)^(2)(大气折射率结构常数)一直稳定在-180~-165 dB,C_(n)^(2)值小于-180 dB时,最大探测高度降至3500 m以下,整层垂直速度小于0.5 m/s,预示降雪结束。

沈阳2次重污染天气过程的风廓线雷达观测结果对比分析

为进一步研究重污染天气的形成机理,利用风廓线雷达资料、常规气象观测资料和大气污染物监测资料,对2015年11月6—10日和2019年3月2—6日(分别简称“过程Ⅰ”和“过程Ⅱ”)沈阳2次重污染天气过程进行对比分析,重点总结风廓线雷达直接探测产品和反演产品的演变特征。结果表明:过程Ⅰ,污染重,污染物浓度增速快,能见度持续偏低,下沉速度大,动力条件更稳定,且雷达接收的气象回波信号强。低层始终维持高强度的暖平流,为污染物浓度达到异常峰值提供强力的暖湿条件。过程Ⅱ,污染相对较轻,冷、暖平流交替出现,使污染物浓度呈波动式上升,增速慢,能见度存在日变化,下沉速度小,且雷达接收的气象回波信号弱。2次重污染过程都受外来污染物输送影响,但输送路径不同。

多源地基遥感资料在郑州强飑线天气预警中的应用

基于风廓线雷达、毫米波云雷达、微波辐射计、雨滴谱等地基遥感探测资料和常规探测资料,研究多源探测资料在郑州强飑线天气预警中的应用.结果表明:①风廓线雷达资料精细地呈现了飑线过程中冷暖平流及垂直风切变的演变,特别是监测到飑线形成前1 h对流层中低层西南急流形成并增厚,深层垂直风切变增强,利于飑线的形成和组织化.②毫米波云雷达产品显示,随着飑线系统移近,云系增多增厚并向下、向上扩展,云中的含水量增大,强反射率因子接地指示降水产生.③微波辐射计反演的温度、湿度及大气不稳定指数在对流发生前后变化特征显著,在飑线临近预警中有一定的参考价值.④雨滴谱数据显示直径2 mm以下的雨滴是此次飑线降水的主要贡献者.

基于风廓线雷达产品的冰雹过程分析

利用贵州省威宁县气象局的风廓线雷达基础数据及其二次开发产品、雨量站和MICAPS的实况数据,对2019年6月11日发生在威宁本站的一次冰雹大风天气过程进行综合分析。结果表明:水平廓线产品可反映出冷暖平流的时空变化及垂直分布,更早探测冷空气入侵、风场切变情况及低空急流强度;大气折射率结构常数和垂直速度可以指示降水的发生、持续时间及降水强度情况;强降水发生前有较强风垂直切变,降水过程中风垂直切变值整体大于0.2 s^(-1),风垂直切变的增强会引起垂直速度和地面大风的增大;若以大于15 dBZ和小于10 dBZ为降水的起止标志,风廓线雷达反射率因子较其他产品可以更清晰地指示降水的开始和结束。

多源观测资料在六盘山西侧一次强对流暴雨中的应用

利用常规气象探测、ERA5逐1 h再分析、区域气象站、X波段双偏振、C波段多普勒及风廓线雷达等多源资料,对2022年7月15日六盘山西侧发生的一次被业务常用数值模式和预报员主观预报均漏报了的强对流暴雨进行综合分析。结果表明:此次暴雨发生在西太平洋副热带高压西北侧,主要落区为低层暖式切变线南侧及低空急流左前侧。在六盘山地形作用下,中尺度地面辐合线、中尺度西南急流和中尺度涡旋可能是此次暴雨的重要触发、维持和增强系统。暴雨由两条中尺度回波带造成,其上对流单体呈后向传播,存在明显的列车效应。地面5 min降水量明显增强前1~2 h,有低空急流加强、垂直风切变增加、急流中风速向下脉动和干侵入等现象,对暴雨预报预警有很好的参考意义。50 dBz以上强度回波面积、垂直积分液态水含量、回波顶高、大范围的差分传播相移(K_(DP))和差分反射率因子(Z_(DR))的大值区对强降水落区有较好的指示意义,K_(DP)能较好反映强降水强度。最大K_(DP)和Z_(DR)均较最强5 min降水提前10 min出现,Z_(DR)弧和Z_(DR)柱也较最强5 min降水提前10~20 min出现。最强降水时段,K_(DP)达3.0~4.0°·km^(-1),对应Z_(DR)为3.0~3.3 dB,相关系数为0.90~0.95,说明雨滴直径大且数浓度大,增加了降水的极端性。

测风激光雷达与风廓线雷达的探测性能评估及数据融合

测风激光雷达和风廓线雷达作为L波段探空测风的有效补充,均可以提供高时空分辨率的大气风场信息,然而由于工作原理和适用条件存在明显差异,在探测性能上各有优缺点,单一设备的探测数据已不能满足精细化预报的要求。本研究使用2020年1—5月北京南郊观象台的L波段探空资料对同址观测的测风激光雷达和风廓线雷达进行了数据质量评估,结果表明测风激光雷达与探空的一致性较高,U、V分量的相关系数分别为0.97和0.98,均方根误差分别为1.1和0.95 m·s^(-1),然而在2 km以上数据获取率较低且偏差较大;风廓线雷达与探空相比,U、V分量的相关系数分别为0.94和0.93,均方根误差分别为2.94和2.91 m·s^(-1),风廓线雷达的探测距离虽然更远,但在0.5 km以下和6 km以上的测量偏差较大。考虑到两种测风雷达在不同探测高度上的性能优缺点,提出分段曲面拟合法对两者的水平风资料进行融合处理,并选取个例对融合效果进行验证,结果表明,融合后的风廓线与融合前相比,风向和风速的一致性均得到明显提升。

综合观测试验中的激光测风雷达探测性能分析

基于2019年6、7月广州超大城市综合观测试验中的地面资料,激光测风雷达、风廓线雷达资料以及广州S波段双偏振雷达资料,对WindPrint S4000型激光测风雷达和风廓线雷达进行观测对比,并尝试在不同降水强度条件下对激光测风雷达的探测性能进行综合评估分析。结果表明:激光测风雷达与风廓线雷达在非降水时段和非强降水时段观测性能一致性较好,能很好地捕捉到天气系统过境期间边界层低空风场的变化特征,但相比较而言,激光测风雷达成本更低,更加便捷高效,选址选点较为容易,更加符合大城市观测加密布网的需求;激光雷达的探测高度与降水量和降水强度均相关,但与降水强度关系更加密切,即当降水强度增加时,激光雷达的探测高度总体呈下降趋势,且当发生S波段双偏振天气雷达反射率因子达到50 dbz以上强度的降水时,激光测风雷达与风廓线雷达一样无法进行常规观测。

风廓线雷达产品在贵州降雪冻雨天气中的特征分析

利用贵阳机场CFL-03型大气边界层风廓线雷达(Wind Profile Radar,WPR)资料、贵阳机场自观资料等,针对典型降雪和冻雨个例,以及贵阳近三年发生的降雪和冻雨过程的特征进行统计分析,结果表明:①WPR的水平风场反应出降雪期间冷空气厚度及强度都超过冻雨,并且中低层主要为冷平流,而冻雨中低层主要为暖平流;②高层大气折射率结构常数C_(n)^(2)增大/减小在时间上超前于降雪的增强/减弱,可以反应降雪强度变化的趋势;③降雪阶段的回波强度分布在垂直方向上向左倾斜,高层回波强度的变化对降雪强度的变化具有指示性;冻雨的回波在垂直方向呈现“强弱强”的分布,与温度场在垂直方向上的“冷-暖-冷”的层结分布一致;④冻雨天气下粒子的下落速度小于降雪,雨夹雪的下落速度比纯雪更大,小雪下落速度最小。

河南北中部一次雨雪冰冻过程的相态特征分析

2023年末河南北中部出现一次大范围雨雪冰冻过程,降水相态复杂多变,并伴有区域性雷暴,较为罕见。利用常规观测、ERA5再分析以及风廓线雷达和双偏振雷达资料等对此次过程的相态特征及成因进行分析。结果表明:(1)500 hPa横槽转竖、南支槽东移,700 hPa西南急流发展,地面先后受东路及西路冷空气影响,导致河南北中部出现持续性大范围雨雪冰冻天气。(2)冷垫以上的条件不稳定性、锋区附近的条件对称不稳定以及强锋生环流上升支为对流天气发生发展提供有利条件,是强雨雪、雷暴及冰雹产生的主要原因。(3)过程中冻雨对应“厚暖层(100-200 hPa)-冷层”层结结构,冰粒对应“冰晶层-薄暖层(50-100 hPa)-冷层”结构,纯雪对应整层冷层,雨夹雪对应近地面出现浅薄暖层。(4)风廓线雷达水平风场产品可定性反映低层西南急流和近地面冷空气强度的变化,不同相态降水的垂直速度产品差异明显,可为相态转变短临的监测和预报提供参考。(5)双偏振产品显示,冻雨和纯雪对应相关系数最大(≥0.99),雨夹雪相关系数最小(0.85~0.9);冰粒中层融化层显著,其高度处差分反射率因子最大,相关系数最小。

成都西部山地和平原过渡区边界层水平风场区域差异分析

利用2022年1月1日至12月31日成都市西部沿山和东部平原地区的风廓线雷达资料,分析大气边界层水平风场垂直结构及日变化趋势的区域差异。结果表明:①成都市边界层低层盛行风向存在东西区域差异,西部山区盛行北东北风,东部平原盛行东北风,且不存在季节差异;边界层中高层盛行风向不存在东西区域差异,表现为与西侧山脉走向一致的东北风和西南风交替出现。②成都市东西部的边界层平均风速廓线变化趋势一致,相同探测高度东部平原的水平风速大于西部沿山。③边界层低层西部沿山地区受局地山谷风影响,在四季均存在显著的水平风向日变化,白天盛行东南风,夜间盛行西北风。④相同探测高度水平风速的日变化特征没有区域差异,在四季基本一致,为单峰单谷型,最小值在白天,最大值在夜间。⑤成都市东西区域的低层大气边界层风场特征的差异主要由西部沿山地区局地复杂地形造成。

京津冀风廓线雷达组网资料评估及应用研究

基于2019年京津冀地区22部风廓线雷达逐小时产品数据,从资料收报率和50%有效数据获取率的探测高度两个角度分析了风廓线雷达探测能力,利用北京探空数据和NCEP1°×1°再分析资料对风廓线雷达水平风廓线数据进行了质量评估,并初步进行了组网资料应用。主要结论如下:(1)风廓线雷达50%有效数据获取率高度69月均能达到指标要求,表现为夏季探测高度高、冬季探测高度低的趋势,边界层风廓线雷达50%有效数据获取率的探测高度最高出现在7月,对流层风廓线雷达的最高出现在8月。(2)风廓线雷达数据和NCEP1°×1°水平风场资料的不同高度层u、v分量的均方根误差平均为3.59 m/s,平均绝对误差平均为2.53 m/s,相关系数平均为0.81,具有最高的可用性,而均方根误差和平均绝对误差从低层到高层整体表现为“增大”趋势。(3)通过风廓线观测资料组网分析,得到不同高度层水平风场、涡度场、散度场及垂直风场等物理量分析产品,并对2019年8月6日一次降雨过程初步进行了产品应用分析,结果显示,组网后的产品能够提供更加精细化的高时空分辨率的物理量分析图,可及时提供更为丰富的高空中尺度水平风场和垂直速度场,能够有效应用到强对流天气分析中。