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radial velocity of ocean surface current estimated from SAR Doppler frequency measurements—a case study of Kuroshio in the East China Sea

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Acta Oceanologica Sinica 2021年第12期40卷 135-147页

作者： Lihua Wang Benwei Shi Yunxuan Zhou Hui Sheng Yanghua Gao Li Fan Ziheng Yang Department of Geography and Spatial Information Techniques/Center for Land and Marine Spatial Utilization and Governance Research Ningbo UniversityNingbo 315211China State Key Laboratory of Estuarine and Coastal Research East China Normal UniversityShanghai 200062China Chongqing Institute of Meteorological Sciences Chongqing 401147China College of Resources and Environment Chengdu University of Information TechnologyChengdu 610225China

Ocean currents are a key element in ocean processes and in meteorology,affecting material transport and modulating climate change patterns.The Doppler frequency shift information of the synthetic aperture radar(SAR)echo signal can reflect the dynamic characteristics of the sea surface,and has become an essential sea surface dynamic remote sensing parameter.Studies have verified that the instantaneous Doppler frequency shift can realize the SAR detection of the sea surface current.However,the validation of SAR-derived ocean current data and a thorough analysis of the errors associated with them remain lacking.In this study,we derive high spatial resolution flow measurements for the Kuroshio in the East China Sea from SAR data using a theoretical model of shifts in Doppler frequency driven by ocean surface current.Global ocean multi observation(MOB)products and global surface Lagrangian drifter(GLD)data are used to validate the Kuroshio flow retrieved from the SAR data.Results show that the central flow velocity for the Kuroshio derived from the SAR is 0.4–1.5 m/s.The error distribution between SAR ocean currents and MOB products is an approximate standard normal distribution,with the 90%confidence interval concentrated between–0.1 m/s and 0.1 m/s.Comparative analysis of SAR ocean current and GLD products,the correlation coefficient is 0.803,which shows to be significant at a confidence level of 99%.The cross-validation of different ocean current dataset illustrate that the SAR radial current captures the positions and dynamics of the Kuroshio central flow and the Kuroshio Counter Current,and has the capability to monitor current velocity over a wide range of values.

关键词： Doppler frequency radial velocity ocean current SAR Kuroshio

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Azimuthal distributions of radial momentum and velocity in relativistic heavy ion collisions

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Chinese Physics C 2012年第5期36卷 423-428页

作者：里霖李娜吴元芳 Institute of Particle Physics Central China Normal University Huazhong University of Science and Technology Brookhaven National Laboratory Key Laboratory of Quark & Lepton Physics (Huazhong Normal University) Ministry of Education

Azimuthal distributions of radial （transverse） momentum, mean radial momentum, and mean radial velocity of final-state particles are suggested for relativistic heavy ion collisions. Using the AMPT transport model with string melting, the distributions of Au＋Au collisions at 200 GeV are presented and studied. It is demonstrated that the distribution of total radial momentum is more sensitive to the anisotropic expansion, as the anisotropies of final-state particles and their associated transverse momentums are both counted in the measurement. The mean radial velocity distribution is compared with the radial flow velocity. The thermal motion contributes an isotropic constant to the mean radial velocity.

关键词： azimuthal distribution radial momentum radial velocity

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Track Initiation Algorithm for Maneuvering Target Using radial velocity Measurements

Track Initiation Algorithm for Maneuvering Target Using Radi...

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第26届中国控制与决策会议

作者： Yuan Junquan Yin Shuai Jiang Jin Wang Licai Air force Early-warning Academy

ISBN: (纸本)9781479937097

Aiming at the track initiation of maneuvering target for track-while-scan（TWS） multiple frequency continuous wave（CW） radar, a new method using the radial velocity measurements is discussed. Firstly, the maneuvering target model and observation model including radial velocity are built. Then the wave gate design and algorithm for track initiation using the radial velocity measurements are analyzed. Finally the performance of target tracking is compared for different wave gate design methods from the view of constant ranging errors and changing errors by Monte Carlo simulation.

关键词： Multiple Frequency CW Radar Maneuvering Target Track Initiation radial velocity

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Efficient approaches of determining the motion of a spherical particle in a swirling fluid flow using weighted residual methods

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Particuology 2015年第6期13卷 68-74页

作者： Seiyed E. Ghasemi M. Vatani D.D. Ganji Young Researchers and Elite Club Qaemshahr Branch Islamic Azad University Qaemshahr lran Department of Mechanical Engineering Babol University of Technology Babol lran

The motion of a spherical particle released in a swirling fluid flow is studied employing the least-squares method and method of moments. The governing equations are obtained and solved employing the two methods. The accuracy of the results is examined against the results of a fourth-order Runge-Kutta numer- ical method. The effects of various parameters, namely the initial radius, initial radial velocity, initial angular velocity, and drag-to-inertia ratio, on the non-dimensional velocity profiles and particle position distribution are considered. The results show that the radial velocity increases over time while the angular velocity decreases, and that an increase in the initial radial velocity increases the particle radial distance and angular velocity but decreases the radial velocity profile.

关键词： Spherical particle Swirling flow radial velocity Angular velocity Least-squares method Method of moments

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Impact of Coastal Radar Observability on the Forecast of the Track and Rainfall of Typhoon Morakot(2009)Using WRF-based Ensemble Kalman Filter Data Assimilation

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Advances in Atmospheric Sciences 2017年第1期34卷 66-78页

作者： Jian YUE Zhiyong MENG Cheng-Ku YU Lin-Wen CHENG Laboratory for Climate and Ocean–Atmosphere Studies Department of Atmospheric and Oceanic SciencesSchool of PhysicsPeking University Department of Atmospheric Sciences NTU

This study explored the impact of coastal radar observability on the forecast of the track and rainfall of Typhoon Morakot （2009） using a WRF-based ensemble Kalman filter （EnKF） data assimilation （DA） system. The results showed that the performance of radar EnKF DA was quite sensitive to the number of radars being assimilated and the DA timing relative to the landfall of the tropical cyclone （TC）. It was found that assimilating radial velocity （Vr） data from all the four operational radars during the 6 h immediately before TC landfall was quite important for the track and rainfall forecasts after the TC made landfall. The TC track forecast error could be decreased by about 43% and the 24-h rainfall forecast skill could be almost tripled. Assimilating Vr data from a single radar outperformed the experiment without DA, though with less improvement compared to the multiple-radar DA experiment. Different forecast performances were obtained by assimilating different radars, which was closely related to the first-time wind analysis increment, the location of moisture transport, the quasi-stationary rainband, and the local convergence line. However, only assimilating Vr data when the TC was farther away from making landfall might worsen TC track and rainfall forecasts. Besides, this work also demonstrated that Vr data from multiple radars, instead of a single radar, should be used for verification to obtain a more reliable assessment of the EnKF performance.

关键词： radial velocity ensemble Kalman filter observability tropical cyclone track rainfall

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A velocity Dealiasing Scheme for C-band Weather Radar Systems

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Advances in Atmospheric Sciences 2014年第1期31卷 17-26页

作者： LI Gang HE Guangxin Xiaolei ZOU Peter Sawin RAY Center of Data Assimilation for Research and Application Nanjing University of Information Science & Technology Department of Earth Ocean and Atmospheric Sciences Florida State University

A dealiasing algorithm for radar radial velocity observed by C-band Doppler radars is presented as an extension of an existing S-band dealiasing algorithm. This has operational significance in that many portable and many commercial broadcast radars, as well as approximately one half of the Chinese weather radar network （CINRAD）, are C-band radars. With a wavelength of about 5 cm, the Nyquist interval of C-band radars is just about one half that of S-band radars （wavelength of about 10 cm） and thus has more velocity folding. The proposed algorithm includes seven modules to remove noisy data, find the starting radials, dealias velocities, and apply least squares error checking in both the radial and azimuth directions. The proposed velocity dealiasing method was applied to one widespread rain case and three strong convective cases from radars operating in China. It was found that, on average, 92.95% of the aliased radial velocity data could be correctly de-aliased by the algorithm, resulting in 96.65% of the data being valid.

关键词： Doppler radar aliasing radial velocity unfolding

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A Method of Autonomous Navigation for Mars Cruise

A Method of Autonomous Navigation for Mars Cruise

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第三十九届中国控制会议

作者： Zipeng Ye Qingrui Zhou Hui Wang Qian Xuesen Laboratory of Space Technology China Academy of Space Technology

This paper proposes a method for autonomous navigation of deep space exploration spacecraft. In order to suppress the error of spacecraft orbit dynamics model in deep space exploration, not only the relative radial velocity of spacecraft, but also the line of sight vector of asteroid is measured. The least squares method is used to calculate the position information obtained from the asteroid line of sight vector, and the improved information fusion method is used to correct the state estimation error caused by the imprecise dynamic model in the extended Kalman filter. Finally, the algorithm is simulated and analyzed. The simulation results show that the dependence of the algorithm on the dynamic model is significantly lower than other algorithms. Under the same model precision, better result can be obtained.

关键词： autonomous navigation radial velocity line of sight vector information fusion

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A New Formula of Redshift vs. Space Expansion and Dark Energy

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Journal of Modern Physics 2021年第3期12卷 229-253页

作者： Olivier Serret ESIM Engineer Cugnaux France

The speed away of stars and galaxies is traditionally calculated from the relativistic formula according to the measurement of the redshift. It is demonstrated here another formula for this speed away of stars and galaxies, from this same redshift z. After having exposed critiques on the demonstration and the relativistic use which require the assumption of an expanding universe by itself, it is proposed within the framework of neo-Newtonian mechanics the formula where V is the speed from the source. This formula has the double characteristic of being equivalent to relativistic predictions for low redshifts, but of deviating from them by up to 17% for high redshifts. It is consistent with the observation of the anisotropy of the Universe and the Cosmic Microwave Background. It helps to explain Pioneer anomalies. It is compatible with the constancy in the majority of cases of interference phenomena. Finally, it provides a new analysis grid for the observation of supernovae, galaxies and distant pulsars, thus opening up new fields of research on the increase in distances attributed to dark energy and also in other areas of the cosmology.

关键词： Redshift Blueshift Dark Energy radial velocity Expansion of the Universe Anisotropy Hubble Law Pioneer Spacecraft Photon Wavelength Frequency Variable Speed Celerity of Light

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