Comparison and error analysis of remotely measured waveheight by high frequency ground wave radar

High frequency ground wave radar (HFGWR) has unique advantage in the survey of dynamical factors, such as sea surface current, sea wave, and sea surface wind in marine conditions in coastal sea area. Compared to marine satellite remote sensing, it involves lower cost, has higher measuring accuracy and spatial resolution and sampling frequency. High frequency ground wave radar is a new land based remote sensing instrument with superior vision and greater application potentials. This paper reviews the development history and application status of high frequency wave radar, introduces its remote-sensing principle and method to inverse offshore fluid, and wave and wind field. Based on the author's "863 Project", this paper recounts comparison and verification of radar remote-sensing value, the physical calibration of radar-measured data and methods to control the quality of radar-sensing data. The authors discuss the precision of radar-sensing data's inversing on offshore fluid field and application of the assimilated data on assimilation.     

利用地物杂波进行天气雷达强度标定

地物杂波的回波强度相对稳定 ,对成都和新疆地区的地物杂波强度的统计表明 ,地物杂波的雷达反射因子方差分别小于 3db和 1.5db ,因此 ,地物回波可作为一个标准目标 ,用来对天气雷达进行强度的标定。本文给出了这种强度标定的流程图、标定方法和标定结果。使用这种标定方法将大大改善天气雷达的维护和使用质量。     

Extraction of internal wave amplitude from nautical X-Band radar observations

One of the most important parameters for oceanic internal waves (IWs) is their amplitude. We have developed a method to retrieve the IW amplitude from nautical X-Band radar images based on the KdV equation for continuous stratified finite depth system. We have also tested the method of measuring the amplitude of IWs from X-Band radar backscatter image sequences acquired on June 2009 in the northeastern South China Sea. The method was applied in several radar images. Experiments show that the retrieval amplitudes are consistent with the in-situ observational amplitudes of IWs by using the towed thermistor chain and conductivity-temperature-depth (CTD) profile. The uncertainty of the method is also discussed.     

Assimilation of high frequency radar data into a shelf sea circulation model

High Frequency (HF) radar current data is assimilated into a shelf sea circulation model based on optimal interpolation (OI) method. The purpose of this work is to develop a real-time computationally highly efficient assimilation method to improve the forecast of shelf current. Since the true state of the ocean is not known, the specification of background error covariance is arduous. Usually, it is assumed or calculated from an ensemble of model states and is kept in constant. In our method, the spatial covariances of model forecast errors are derived from differences between the adjacent model forecast fields, which serve as the forecast tendencies. The assumption behind this is that forecast errors can resemble forecast tendencies, since variances are large when fields change quickly and small when fields change slowly. The implementation of HF radar data assimilation is found to yield good information for analyses. After assimilation, the root-mean-square error of model decreases significantly. Besides, three assimilation runs with variational observation density are implemented. The comparison of them indicates that the pattern described by observations is much more important than the amount of observations. It is more useful to expand the scope of observations than to increase the spatial interval. From our tests, the spatial interval of observation can be 5 times bigger than that of model grid.     

Empirical formula for wave length of ocean wave in finite depth water

In this paper, function characteristics of dispersion of ocean wave in finite depth water were analyzed systematically. The functional form of the fitting function is reasonably proposed, in which the parameters are optimally determined by the least square method （LSM）. For infinitely deep and extremely shallow water,the fitting function fits strictly the dispersion to be fitted. A new technique is presented in application of LSM.An empirical formula with maximum error of less than 0.5% for computing wavelength in finite depth water is presented for practical applications.     

基于VAP方法的多普勒雷达风场反演研究

采用VAP(Velocity Azimuth Processing)方法反演多普勒雷达风矢量场,在利用各个距离圈径向速度随方位角分布的廓线推算风向和风速的设计中,要求基数据速度资料中没有明显的脉动.介绍了在多普勒天气雷达风场反演设计中,直接将方格法的速度资料处理过程融入到方格法风场反演的过程中,利用距离方格内保持中尺度特性的特点,不改变原始资料的同时保证风场反演的正确性.     

A wave modulation model of ripples over long surface waves

A study is presented on the modulation of ripples induced by a long surface wave (LW) and a new theoretical modulation model is proposed. In this model, the wind surface stress modulation is related to the modulation of ripple spectrum. The model results show that in the case of LW propagating in the wind direction with the wave age parameter of LW increasing, the area with enhanced shear stress shifts from the region near the LW crest on the upwind slope to the LW trough. With a smaller wave age parameter of LW, the ripple modulation has the maximum on the upwind slope in the vicinity of LW crest, while with a larger parameter the enhancement of ripple spectrum does not occur in that region. At low winds the amplitude of ripple modulation transfer function (MTF) is larger in the gravity wave range, while at moderate or high winds it changes little in the range from short gravity waves to capillary waves.     

Preliminary validation of high performance liquid chromatography method for detection of methyl-testosterone residue in carp muscle

The use of synthetic anabolic steroid methyltestosterone （MT） as growth promoter is prohibited in China. Validations of analytical methods for MT residue in food and the results obtained have become indispensable. The high performance liquid chromatography （HPLC） method for the detection of MT with liquid-liquid extraction by trichloromethanemethanol in carp muscle tissue was preliminarily validated with reference to the following parameters： recovery （accuracy） at the 1, 5 and 10 mgkg^-1 level, between-run and within-run CV values （repeatability, also called relative standard deviation （RSD）） and limit of detection. The recoveries were above 80% and the between-run and within-run CV values below 10% for muscle tissue. The limit of detection was 0.05 mgkg^-1.     

一种基于卷积的正弦波频率稳定度测量方法

提出了通过离散卷积实现对频率稳定度的测量,介绍了该方法的原理和实现过程,并且与通用的硬件频率测量仪器进行比较,结果表明,与仪器测量频率稳定度的方法相比,此方法灵活简单,测量精度和仪器测量结果一致性较好.     

高精度测频方案设计

介绍了一种基于数字频率计原理 ,以AT89C5 1单片机为控制器件的新型频率测量方法。论述了基本原理和软硬件实现 ,并对其误差进行了分析。克服了通用频率计由于± 1MSB误差在高低频段测量精度不等的缺陷 ,实现了高低频率的等精度测量。由于此方法具有高精度、低成本、易改进的特点 ,因此具有一定的实用性。     

基于FPGA的风廓线雷达信号定时器的设计和实现

详细介绍了信号定时器的特点和工作原理,并给出一种基于现场可编程门阵列(FPGA)的风廓线雷达信号定时器的设计方法.该信号定时器在某风廓线雷达中成功应用,且运行可靠,效果良好.     

一种CINRAD雷达基数据读取丢失的改进方法

多普勒天气雷达是目前世界上最先进的气象雷达,已成为对灾害性天气监测、预警的重要手段之一.雷达基数据的读取是做雷达应用软件的基础,针对目前常规方法对雷达基数据的读取遇到的数据丢失的问题,提出一种改进方法.通过对大量数据的分析和读取,发现新的方法能够有效地提取出丢失数据,并且能够根据丢失数据的重要性对图像进行修正,对小尺度龙卷天气的分析有重要意义.     

The fractional power law of wind wave growth in deep water for short fetch

Combining the 3/2 power law proposed by Toba with the significant wave energy balance equation for wind waves, wave growth in deep water for short fetch is investigated. It is found that the variations of wave height and period with fetch have the form of power function with fractional exponents 3/8 and 1/4 respectively. Using these exponents in the power functions and through data fitting, the concise wind wave growth relations for short fetch are obtained.     

Parameterized first-guess spectrum method for retrieving directional spectrum of swell-dominated waves and huge waves from SAR images

A method to retrieve ocean wave spectra from SAR images, named Parameterized First-guess Spectrum Method (PFSM), was proposed after interpretation of the theory to ocean wave imaging and analysis of the drawbacks of the retrieving model generally used. In this method, with additional information and satellite parameters, the separating wave-number is first calculated to determine the maximum wave-number beyond which the linear relation can be used. The separating wave-number can be calculated using the additional information on wind velocity and parameters of SAR satellite. And then the SAR spectrum can be divided into SAR spectrum of wind wave and of swell according to the result of separating wave-number. The portion of SAR spectrum generated by wind wave, is used to search for the most suitable parameters of ocean wind wave spectrum, including propagation direction of ocean wave, phase speed of dominating wave and the angle spreading coefficient. The swell spectrum is acquired by directly inversing the linear relation of ocean wave spectrum to SAR spectrum given the portion of SAR spectrum generated by swell. We used the proposed method to retrieve the ocean wave spectrum from ERS-SAR data from the South China Sea and compared the result with altimeter data. The agreement indicates that the PFSM is reliable.     

EXPLORATION ON METHOD OF AUTO-CLASSIFICATION FOR MAIN GROUND OBJECTS OF THREE GORGES RESERVOIR AREA

1IN TR O DU C TIO N With thedevelopmentof remotesensingtechnolog,y thestudyandapplicatioonftheautomaticclassifitciaon method usingcomputerhad achievedsatisfyi ndgevel- opment. From spectrumstatisticcallassificatitoonthe neural network classificatimoenthod…     

Spatial distribution characteristics of surface tidal currents in the southwest of Taiwan Strait

This study was conducted on the spatial distribution characteristics of surface tidal currents in the southwestern Taiwan Strait based on the quasi-harmonic analysis of current data obtained by two high frequency surface wave radar (HFSWR) systems. The analysis shows that the tidal current pattern in the southwestern Taiwan Strait is primarily semi-diurnal and influenced significantly by shallow water constituents. The spatial distribution of tidal current ellipses of M₂ is probably affected by the interaction between two different systems of tide wave, one from the northern mouth of Taiwan Strait and the other from the Bashi Channel. The directions of the major axes of M₂ tidal current ellipses coincide roughly with the axis of the Taiwan Strait. The spatial distribution of the magnitudes of the probable maximum current velocity (PMCS) shows gradual increase of the velocity from northeast to southwest, which is in accordance with the spatial distribution of the measured maximum current velocity (MMCS). The directions of the residual currents are in accordance with the direction of the prevailing monsoon wind at the Taiwan Strait and the direction of the Taiwan warm current during summer. The bathymetry also shows a significant effect on the spatial distribution characteristics of tidal currents.