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.

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.

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.

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.

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.

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.

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。

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。

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。

面向空中风力发电系统的高空风场观测

[目的]文章旨在研究空中风力发电系统(Airborne Wind Energy System,AWES)的测风需求及设备选型。[方法]以某空中风力发电示范工程为依托,开展测风激光雷达与风廓线雷达的对比观测试验,并对数据获取率、垂直廓线特征和时间变化特征进行分析。[结果]结果显示:在3 km高度范围内,测风激光雷达的数据获取率随高度递减至不足0.4,风廓线雷达的数据获取率则维持在0.98以上,具有更好的观测适应性;两种测风设备的风速、风向垂直廓线以及逐日、多日波动特征均具有一致性,并且能被再分析资料和高空气象站同期探空资料所验证。测风激光雷达观测结果的中位数、极差、标准差等统计特征与再分析资料更接近,相关性更好;风廓线雷达观测结果的极差和标准差整体偏大,测风精度不及测风激光雷达。[结论]文章研究表明,应根据项目所在地的气候状况,在空中风力发电站工程的不同设计阶段合理选择测风设备,科学设置测风方式。

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。

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。

南宁机场2次低云过程对比分析

该文利用云高仪资料、ERA5(0.25°×0.25°)再分析资料以及风廓线雷达资料对南宁机场2023年1月和2月2次低云过程进行对比分析,结果表明,①2次过程均伴随降水,差别在于2月过程低云持续时间更长,期间出现一次大雾天气;②2次过程均受西南急流影响,后期中层西北气流和地面西南低压外围形势是2次过程低云消散的关键,差别在于2月过程低层切变线的维持和地面弱冷空气的渗透使得低云更容易生成和维持;③2次过程低层都存在湿区且近地层存在逆温层,差别在于2月过程的逆温层深厚且长时间维持,逆温层高度的下降,是2月过程出现大雾的重要原因之一;④1月过程为冷暖交汇型低云转纯回流型低云,2月过程以冷暖交汇型低云为主,短时为纯回流型低云;⑤V0H对于低云的预报有一定的指示意义,当南北特征值都存在时,南风特征值的增大有利于低云的出现,当只存在南风特征值时,大于等于8 m/s的南风特征值有利于低云的消散;⑥2次过程云底高度的升降与垂直运动的方向呈现正相关关系。

一次冷涡背景下强对流过程中风廓线雷达的应用

该文利用南通市兴东国家站风廓线雷达提供的资料,通过统计方法分析2017年8月7日南通出现的一次强对流天气过程。结果表明,此次强对流天气发生在冷涡背景下,处在副高边缘,本地水汽条件较好。风廓线雷达在强对流发生前能够清晰地体现冷暖平流的分布,风向风速的变化,对强对流过程的预报预警有很好的指示意义。垂直速度和信噪比与对流发生趋势较为一致,能够较好反映对流的变化。大气折射率结构常数能够很好地反映强对流的发生和结束。垂直风切变在强对流发生前60 min出现明显增大。

昆明长水机场两次静止锋雷暴过程对比和保障难点分析

运用常规探空观测资料、风廓线雷达和多普勒雷达资料对2019年8月13-14日和2020年6月13-14日两次典型的静止锋雷暴天气和保障过程进行对比分析。两次天气均是昆明准静止锋配合500hPa槽后西北气流和700hPa切变线南压的过程,不同之处在于2019年8月13-14日700hPa本场处于滇中槽前,而2020年6月13-14日位于西太平洋副高西南侧东南气流控制。二者的区别也造成了航班影响状况的不同,前者是锋面从东北面过境先后造成本场和五边延长线雷雨,后者是锋面迅速过境后首先造成五边延长线长时间雷雨覆盖,然后随着锋面的北退才造成本场雷雨,与前者影响顺序正好相反,且两次过程主要影响的时段都是每日0-2点的回港小高峰。

基于高斯拟合的复杂环境地杂波自适应抑制方法

针对风廓线雷达受到强地物杂波干扰探测数据存在较大偏差,使用常规地杂波抑制方法处理存在局限性这一问题进行研究,提出对功率谱数据进行基于高斯拟合自适应去地杂波处理的方法。通过数据验证,提出的算法能够有效抑制地物杂波信号,减少对有用回波信号识别的干扰。

基于风廓线雷达的贵州中部一次强对流天气特征分析

【目的】为了分析风廓线雷达对强对流的探测能力及临近预警指标。【方法】利用风廓线雷达基本和反演参量及常规气象资料,对2023年3月16日贵州中部大范围混合性强对流天气进行分析。【结果】此次过程是在高空槽、低层切变线、低空急流及有利的环境条件共同作用下,由地面辐合线和冷锋先后触发形成的。风廓线雷达水平风场能探测槽线、切变线及地面冷空气的准确过境时间及低空急流的变化,较常规地面和高空资料优势明显。【结论】(1)风廓线雷达反演的温度平流、垂直风切变产品可以反映降雹区周边环境的层结不稳定和低层较强垂直风切变特征以及强降水发生时强冷平流入侵和整层深厚强垂直风切变特征,低空急流指数跃增后消失指示了短时强降水的发生。(2)垂直速度≥4 m·s-1、谱宽≥1 m·s-1、大气折射率结构常数C_n2≥-130 dB,信噪比SNR≥50 dB可作为划分有无降水的界限,且垂直速度和谱宽的伸展高度有助于区分对流性和稳定性降水阶段。