A New Method for Deriving High-Vertical-Resolution Wind Vector Data from the L-Band Radar Sounding System in China

High-vertical-resolution radiosonde wind data are highly valuable for describing the dynamics of the meso-and microscale atmosphere. However, the current algorithm used in China's L-band radar sounding system for calculating highvertical-resolution wind vectors excessively smooths the data, resulting in significant underestimation of the calculated kinetic energy of gravity waves compared to similar products from other countries, which greatly limits the effective utilization of the data. To address this issue, this study proposes a novel method to calculate high-vertical-resolution wind vectors that utilizes the elevation angle, azimuth angle, and slant range from L-band radar. In order to obtain wind data with a stable quality, a two-step automatic quality control procedure, including the RMSE-F(root-mean-square error F) test and elemental consistency test are first applied to the slant range data, to eliminate continuous erroneous data caused by unstable signals or radar malfunctions. Then, a wind calculation scheme based on a sliding second-order polynomial fitting is utilized to derive the high-vertical-resolution radiosonde wind vectors. The evaluation results demonstrate that the wind data obtained through the proposed method show a high level of consistency with the high-resolution wind data observed using the Vaisala Global Positioning System and the data observed by the new Beidou Navigation Sounding System. The calculation of the kinetic energy of gravity waves in the recalculated wind data also reaches a level comparable to the Vaisala observations.

Retrieval algorithm of sea surface wind vectors for WindSat based on a simple forward model

WindSat/Coriolis is the first satellite-borne polarimetric microwave radiometer, which aims to improve the potential of polarimetric microwave radiometry for measuring sea surface wind vectors from space. In this paper, a wind vector retrieval algorithm based on a novel and simple forward model was developed for WindSat. The retrieval algorithm of sea surface wind speed was developed using multiple linear regression based on the simulation dataset of the novel forward model. Sea surface wind directions that minimize the difference between simulated and measured values of the third and fourth Stokes parameters were found using maximum likelihood estimation, by which a group of ambiguous wind directions was obtained. A median filter was then used to remove ambiguity of wind direction. Evaluated with sea surface wind speed and direction data from the U.S. National Data Buoy Center （NDBC）, root mean square errors are 1.2 rn/s and 30~ for retrieved wind speed and wind direction, respectively. The evaluation results suggest that the simple forward model and the retrieval algorithm are practicable for near-real time applications, without reducing accuracy.

Influence of Wind Vector Structure Variation of Typhoon "Catfish" Circulation on Its Pathway Mutation

[Objective] The research aimed to study the wind vector structure variation of No.1013 strong typhoon 'catfish',and its influence on typhoon pathway mutation.[Method] According to the theory that the asymmetric structure of typhoon vortex had influence on typhoon movement,the center of No.1013 super typhoon 'catfish' was as the coordinate origin,and 850,500 hPa tangential rotation speeds within 300-500 km were decomposed into u and v components.The composite force movement tendency of typhoon was analyzed.The wind vector structure variation of No.1013 strong typhoon 'catfish' and its influence on typhoon pathway mutation were discussed.[Result] At the quick movement stage of No.1013 strong typhoon,the wind vector had obvious asymmetric structure.When the typhoon rotated in situ,the wind vector presented symmetric structure.When ΔU,ΔV and composite wind vector had obvious variations,the composite force of typhoon changed,and the moved direction also would change.The asymmetric structure of wind speed near 300-500 km around 500 and 850 hPa typhoon centers was favorable for tendency of moved pathway.The pointed directions of ΔU,ΔV and composite wind vector could be as the direction of composite force movement of typhoon.[Conclusion] The research provided reference basis for typhoon prevention.

An advanced wind vector retrieval algorithm for the rotating fan-beam scatterometer

The rotating fan-beam scatterometer （RFSCAT） is a new type of satellite scatterometer that is proposed approximately 10 a ago. However, similar to other rotating scatterometers, relatively larger wind retrieval errors occur in the nadir and outer regions compared with the middle regions of the swath. For the RFSCAT with the given parameters, a wind direction retrieval accuracy decreases by approximately 9 in the outer regions compared with the middle region. To address this problem, an advanced wind vector retrieval algorithm for the RFSCAT is presented. The new algorithm features an adaptive extension of the range of wind direction for each wind vector cell position across the whole swath according to the distribution histogram of a retrieved wind direction bias. One hundred orbits of Level 2A data are simulated to validate and evaluate the new algorithm. Retrieval experiments demonstrate that the new advanced algorithm can effectively improve the wind direction retrieval accuracy in the nadir and outer regions of the RFSCAT swath. Approximately 1.6 and 9 improvements in the wind direction retrieval are achieved for the wind vector cells located at the nadir and the edge point of the swath, respectively.

Vector Dominating Multi-objective Evolution Algorithm for Aerodynamic-Structure Integrative Design of Wind Turbine Blade

A novel multi-objective optimization algorithm incorporating vector method and evolution strategies,referred as vector dominant multi-objective evolutionary algorithm(VD-MOEA),is developed and applied to the aerodynamic-structural integrative design of wind turbine blades.A set of virtual vectors are elaborately constructed,guiding population to fast move forward to the Pareto optimal front and dominating the distribution uniformity with high efficiency.In comparison to conventional evolution algorithms,VD-MOEA displays dramatic improvement of algorithm performance in both convergence and diversity preservation when handling complex problems of multi-variables,multi-objectives and multi-constraints.As an example,a 1.5 MW wind turbine blade is subsequently designed taking the maximum annual energy production,the minimum blade mass,and the minimum blade root thrust as the optimization objectives.The results show that the Pareto optimal set can be obtained in one single simulation run and that the obtained solutions in the optimal set are distributed quite uniformly,maximally maintaining the population diversity.The efficiency of VD-MOEA has been elevated by two orders of magnitude compared with the classical NSGA-II.This provides a reliable high-performance optimization approach for the aerodynamic-structural integrative design of wind turbine blade.

基于全极化微波辐射计WindSat亮温数据的海面风场反演

根据全极化微波辐射传输理论,利用双尺度模式建立了海面辐射亮温的反演算法,并且利用美国发射的全球第一个星载全极化微波辐射计(WindSat)在轨运行期间的亮温数据进行了海面风场的反演,重点分析了风向反演的模糊度问题,并对风场反演结果进行了评估。研究结果初步验证了全极化辐射计在卫星上遥感海面风场的能力:与美国国家环境预报中心(NECP)的数据进行比较,反演的风速误差为1.15m/s,5m/s 以上风速下的风向误差为21°;与 TAO 浮标数据进行比较,风速误差为1.4m/s,风速5m/s 以上的风向误差为20.5°。

一种针对Windsat极化辐射计的海面风场反演方法

星载极化微波辐射计(Windsat)是美国于2003年1月6日发射的全球第一颗星载极化微波辐射计卫星,目的是为了验证极化辐射计在卫星上遥感海面风场的能力。针对Windsat在轨运行期间的数据,研究了风场反演的海洋和大气算法,进行了全球海面风场的反演,同时反演出其它地球物理参数。最后利用同步的其它数据对反演结果进行了验证。本文在极化辐射计风场反演方法和算法研究方面做了初步的尝试。

Comparison of Wind Sat and buoy-measured ocean products from 2004 to 2013

To evaluate the ocean surface wind vector and the sea surface temperature obtained from WindSat, we compare these quantities over the time period from January 2004 to December 2013 with moored buoy measurements. The mean bias between the WindSat wind speed and the buoy wind speed is low for the low frequency wind speed product （WSPD_LF）, ranging from -0.07 to 0.08 m/s in different selected areas. The overall RMS error is 0.98 m/s for WSPD_LF, ranging from 0.82 to 1.16 m/s in different selected regions. The wind speed retrieval result in the tropical Ocean is better than that of the coastal and offshore waters of the United States. In addition, the wind speed retrieval accuracy ofWSPD LF is better than that of the medium frequency wind speed product. The crosstalk analysis indicates that the WindSat wind speed retrieval contains some cross influences from the other geophysical parameters, such as sea surface temperature, water vapor and cloud liquid water. The mean bias between the WindSat wind direction and the buoy wind direction ranges from -0.46° to 1.19° in different selected regions. The overall RMS error is 19.59° when the wind speed is greater than 6 m/s. Measurements of the tropical ocean region have a better accuracy than those of the US west and east coasts. Very good agreement is obtained between sea surface temperatures of WindSat and buoy measurements in the tropical Pacific Ocean; the overall RMS error is only 0.36℃, and the retrieval accuracy of the low latitudes is better than that of the middle and high latitudes.

A Revised Satellite Cloud-Derived Wind Inversion Algorithm Based on Computer Cluster

In view of the satellite cloud-derived wind inversion has the characteristics of large scale,intensive computing and time-consuming serial inversion algorithm is very difficult to break through the bottleneck of efficiency.We proposed a parallel acceleration scheme of cloud-derived wind inversion algorithm based on MPI cluster parallel technique in this paper.The divide-and-conquer idea,assigning winds vector inversion tasks to each computing unit,is identified according to a certain strategy.Each computing unit executes the assigned tasks in parallel,namely divide-and-rule the inversion task,so as to reduce the efficiency bottleneck of long inversion time caused by serial time accumulation.In the scheme of parallel acceleration based on MPI cluster,an algorithm based on performance prediction is proposed to effectively implement load balance of MPI clusters.Through the comparative analysis of experiment data using the parallel scheme of this parallel technology framework,it shows that this parallel technology has a certain acceleration effect on the cloud-derived wind inversion algorithm.The speedup of the MPI-based parallel algorithm reaches 14.96,which achieved the expected estimate.At the same time,this paper also proposes an efficiency optimization algorithm for cloud-derived wind inversion.In the case that the inversion of wind vector accuracy loss is minimal,the optimized algorithm execution time can be up to 13 times faster.

Wind rotation characteristics of the upper tropospheric monsoon over the central and eastern tropical Pacific

In this study, to investigate whether the variation of wind direction in the upper tropospheric monsoon over the central and eastern tropical Pacific shows similar characteristics to the classical monsoon region, the authors introduced a wind vector angle methodology that describes the size of the angle of the wind direction variation, as well as the directed rotary angle, which includes not only the size of the angle but also how the wind vector rotates. On this basis, the authors utilized and improved the directed rotary angle methodology to investigate the evolution of wind direction in detail, and the study confirmed the presence of the same four rotation features in the upper tropospheric monsoon region. Furthermore, the authors also identified the precise variation of wind direction in pentads with seasonal evolution, and found the onset time of the upper tropospheric monsoon may be earlier than the classical monsoon while the termination time may be later. The results further support and supplement the theory of global monsoons, which unifies the low-level and upper tropospheric monsoon as one monsoon system.

用SeaWinds散射计数据反演海面风矢量的神经网络模型

针对构建用 SeaWinds 散射计数据反演海面风矢量的神经网络模型所面临的主要问题,结合 SeaWinds 散射计的几何观测特征,提出了适合 SeaWinds 散射计旋转圆锥扫描方式的先风向后风速的两步神经网络反演模型及相应算法,并采用两组不同的 L2A 和相应 L2B 数据及浮标数据对该神经网络反演模型进行了初步验证。实验结果证明了该神经网络反演模型的可行性。与最大似然估计(MLE)反演方法相比,该神经网络反演模型在能够保证反演精度的情况下,运行效率提高了约5倍,从而为海面风矢量的实时反演提供了可能性。

全极化微波辐射成像仪WindSat海面风矢量反演简化正向模型

WindSat是世界上第1个星载全极化微波辐射成像仪,其海面风矢量的反演基于较复杂的双尺度海面辐射正向模型以及非线性优化算法。1个简单而足够准确的正向模型将可提供快速的反演算法。本文利用WindSat提供的Stokes参数以及同步的QuikScat海面风矢量、TMI海表温度/大气水汽总量/液态水总量构成的数据集,建立了WindSat的简化正向模型。其中,垂直/水平极化亮温风速模型基于改进的Wentz模型,Stokes3/4参数风向模型基于统计回归方法。简化正向模型模拟结果与WindSat观测数据比较,以10.7GHz为例,4个Stokes参数的均方根误差分别为0.52、0.42、0.34、0.22K。

The Performance of Dual-Frequency Polarimetric Scatterometer in Sea Surface Wind Retrieval

The wind retrieval performance of HY-2 A scanning scatterometer operating at Ku-band in HH and VV polarizations has been well evaluated in the wind speed range of 0–25 m s^-1.In order to obtain more accurate ocean wind field,a potential extension of dual-frequency(C-band and Ku-band)polarimetric measurements is investigated for both low and very high wind speeds,from 5 to 45 m s^-1.Based on the geophysical model functions of C-band and Ku-band,the simulation results show that the polarimetric measurements of Ku-band can improve the wind vector retrieval over the entire scatterometer swath,especially in nadir area,with the wind direction root-mean-square error(RMSE)less than 12?in the wind speed range of 5–25 m s^-1.Furthermore,the results also show that C-band cross-polarization plays a very important role in improving the wind speed retrieval,with the wind speed retrieval accuracy better than 2 m s^-1 for all wind conditions(0–45 m s^-1).For extreme winds,the C-band HH backscatter coefficients modeled by CMOD5.N(H)and the ocean co-polarization ratio model at large incidence are used to retrieve sea surface wind vector.This result reveals that there is a big decrease of wind direction retrieval RMSE for extreme wind fields,and the retrieved result of C-band HH polarization is nearly the same as that of C-band VV polarization for low-to-high wind speed(5–25 m s^-1).Thus,to improve the wind retrieval for all wind conditions,the dual-frequency polarimetric scatterometer with C-band and Ku-band horizontal polarization in inner beam,and C-band horizontal and Ku-band vertical polarization in outer beam,can be used to measure ocean winds.This study will contribute to the wind retrieval with merged satellites data and the future spaceborne scatterometer.

Intelligent control for large-scale variable speed variable pitch wind turbines

Large-scale wind turbine generator systems have strong nonlinear multivariable characteristics with many uncertain factors and disturbances. Automatic control is crucial for the efficiency and reliability of wind turbines. On the basis of simplified and proper model of variable speed variable pitch wind turbines, the effective wind speed is estimated using extended Kaiman filter. Intelligent control schemes proposed in the paper include two loops which operate in synchronism with each other. At below-rated wind speed, the inner loop adopts adaptive fuzzy control based on variable universe for generator torque regulation to realize maximum wind energy capture. At above-rated wind speed, a controller based on least square support vector machine is proposed to adjust pitch angle and keep rated output power. The simulation shows the effectiveness of the intelligent control.

星下点观测的星载卫星导航反射信号海面风矢量极大似然估计

该文针对星载全球导航卫星反射计(GNSS-R)镜面反射信号对海面风向不敏感导致海面风向反演难问题,分析非镜向海面散射信号特征,提出星下点非镜向观测模式,定义该模式下海面风矢量敏感特征观测量,在此基础上提出基于星载GNSS-R海面风矢量极大似然估计(MLE)反演算法直接利用两颗及以上导航卫星的星下点非镜向散射信号进行海面风矢量的反演,并提出风矢量搜索算法提高反演效率。通过搭建星载GNSS-R仿真平台验证算法的可行性和评估算法性能。结果表明:所提算法可直接利用非镜向独立观测模式下的多颗导航卫星散射信号反演得到海面风速和风向;多星观测可消除观测几何导致的模糊解从而将海风风向4个模糊解降至2个模糊解,但无法消除海浪谱的对称性导致的海面风向模糊解。在2~25 m/s的风速内,当信噪比(SNR)大于11 dB时,3星观测的风速均方根误差(RMSE)优于2 m/s,风向的均方根误差优于15°。

Exact calculation of the minimal thickness of the large optical path difference wind imaging interferometer

This paper gives the relation between spatial ray and its projection on paper plane based on the vector form of reflective law. Using the method of prism expansion, it obtains the exact expression of the exit height. The exit height can ensure that the incident rays, at arbitrary direction and arbitrary angle, after several transmission and reflection in the two right-angle reflectors, finally pass through the exit surface. Furthermore, it analyses the effects of different parameters on the exit height through computer simulation, and some important conclusions are obtained. The physical meaning of the sign of exit height is described, and the exact expression of the minimal thickness of the large optical path difference wind imaging interferometer is gained. This work is of great scientific significance to the static, real- time simultaneous detection of atmospheric wind field, and it will provide a theoretical and practical guidance for the miniaturization design and engineering realization of wind imaging interferometer.

基于人工智能的非高斯风压预测虚拟仿真实验教学

利用有限的随机风场时程数据预测未知点位置的随机风场时程,以实现虚拟仿真实验教学的目的,可在一定程度上节省实验费用和资源,降低实验测试难度。利用Matlab仿真软件建立基于支持向量机(SVM)非高斯风压预测仿真方法。仿真结果表明,SVM核函数的选择对非高斯风压预测仿真影响较大,线性核函数模型对非高斯风压的预测仿真效果优于高斯核函数与指数核函数。基于SVM线性核函数模型能有效预测非高斯风压,为风洞试验或风场实测的虚拟仿真教学提供借鉴。

一种基于静止卫星的海面风矢量估测方法

参考大气动力学理论中风随高度、纬度的分布特征,提出一种基于静止卫星低层大气导风利用全连接神经网络估测海面风的新思路,构建基于卫星遥感数据的全连接神经网络海面风矢量估测模型,实现基于大气导风的海面风估测。基于GOES-16先进基线成像仪可见光通道0.5 km分辨率大气导风开展试验,并与2021年1月1日—12月31日北美近海岸和海上93个美国国家数据浮标中心浮标数据比对,结果表明:全连接神经网络估算得到基于大气导风的海面风风速均方根误差不大于1.5 m·s^(-1),较传统模型降低0.24 m·s^(-1)。将模型应用于飓风场景,通过与2022年3个北大西洋飓风和3个东太平洋飓风共13个时次的再分析数据比对表明:基于大气导风的海面风风速均方根误差不大于1.1 m·s^(-1),相较于传统经验模型降低0.04 m·s^(-1),在低风速区无系统性偏差。

基于频率响应与图像特征提取的动车组变压器绕组状态诊断方法研究

动车组变压器是保障高速铁路稳定运行的核心设备,频率响应法是目前检测变压器绕组状态的有效方法。为提升车载变压器绕组状态诊断的准确性,结合暂态信号与频率响应法提出基于频率响应与图像特征提取的动车组变压器绕组状态诊断方法。搭建试验车载变压器绕组故障模拟平台,获取不同故障类型和故障位置的频响曲线,利用类Gram矩阵结合幅频和相频曲线信息,再利用密度分层法转换为伪彩色图,提取对应的灰度共生矩阵和灰度差分矩阵特征值,根据鹈鹕优化支持向量机方法对绕组故障进行诊断。试验结果表明:车载变压器绕组故障发生时,伪彩色图能够反映出故障信息,有利于图像分析和特征提取,采用基于频率响应与图像特征提取的动车组变压器绕组状态诊断方法能够识别车载变压器绕组的典型故障类型和位置。

利用双通道激光雷达验证低信噪比反演算法

针对相干测风激光雷达(LiDAR)在低信噪比(SNR)下反演算法的可靠性和精度难以验证的问题,搭建了一种双通道的脉冲相干测风LiDAR系统,可以同时获取高、低SNR的2组数据,并使用高SNR通道的结果作为真值,比较利用不同的算法在低SNR通道进行矢量风速估计的结果。该系统避免了使用其他观测设备作为真值时难以配准或观测目标不统一的问题。本文研究利用雷达获取的观测结果验证了各个算法的有效性,并在各个算法间进行了横向对比。最终,依据各个算法的性能表现和计算复杂度,指明了各个算法具有优势的使用场景。该结果对于充分利用现有系统、使用新算法提高低SNR下的数据获取效率,或在指定探测指标的前提下降低激光能量等硬件要求、实现系统小型化有一定意义。