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Journal articles on the topic 'Doppler radar'
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Gong, Jiangkun, Jun Yan, Deren Li, and Deyong Kong. "Detection of Micro-Doppler Signals of Drones Using Radar Systems with Different Radar Dwell Times." Drones 6, no. 9 (September 19, 2022): 262. http://dx.doi.org/10.3390/drones6090262.
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Not any radar dwell time of a drone radar is suitable for detecting micro-Doppler (or jet engine modulation, JEM) produced by the rotating blades in radar signals of drones. Theoretically, any X-band drone radar system should detect micro-Doppler of blades because of the micro-Doppler effect and partial resonance effect. Yet, we analyzed radar data detected by three radar systems with different radar dwell times but similar frequency and velocity resolution, including Radar−α, Radar−β, and Radar−γ with radar dwell times of 2.7 ms, 20 ms, and 89 ms, respectively. The results indicate that Radar−β is the best radar for detecting micro-Doppler (i.e., JEM signals) produced by the rotating blades of a quadrotor drone, DJI Phantom 4, because the detection probability of JEM signals is almost 100%, with approximately 2 peaks, whose magnitudes are similar to that of the body Doppler. In contrast, Radar−α can barely detect any micro-Doppler, and Radar−γ detects weak micro-Doppler signals, whose magnitude is only 10% of the body Doppler’s. Proper radar dwell time is the key to micro-Doppler detection. This research provides an idea for designing a cognitive micro-Doppler radar by changing radar dwell time for detecting and tracking micro-Doppler signals of drones.
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Baranov, G., R. Gabruk, and I. Gorishna. "Features of Usіng Pulse-Doppler Radars for Determіnatіon Low-Altіtude Targets." Metrology and instruments, no. 2 (May 3, 2019): 62–66. http://dx.doi.org/10.33955/2307-2180(2)2019.62-66.
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In this paper, we analyzed the features of Doppler processing in radars. In ground based radars, the amount of clutter in the radar receiver depends heavily on the radar-to-target geometry. The amount clutter is considerably higher when the radar beam has to face toward the ground. Furthermore, radars employing high PRFs have to deal with an increased amount of clutter due to folding in range. Clutter introduces additional difficulties for airborne radars when detecting ground targets and other targets flying at low altitudes. This is illustrated in Fig. 10.5. Returns from ground clutter emanate from ranges equal to the radar altitude to those which exceed the slant range along the main-beam, with considerable clutter returns in the side-lobes and main-beam. The presence of such large amounts of clutter interferes with radar detection capabilities and makes it extremely difficult to detect targets in the look-down mode. This difficulty in detecting ground or low altitude targets has led to the development of pulse Doppler radars where other targets, kinematics such as Doppler effects are exploited to enhance detection. Pulse Doppler radars utilize high PRFs to increases the average transmitted power and rely on target's Doppler frequency for detection. The increase in the average transmitted power leads to an improved SNR which helps the detection process. However, using high PRFs compromise the radar's ability to detect long range target because of range ambiguities associated with high PRF applications.
Techniques such as using specialized Doppler filters to reject clutter are very effective and are often employed by pulse Doppler radars. Pulse Doppler radars can measure target Doppler frequency (or its range rate) fairly accurately and use the fact that ground clutter typically possesses limited Doppler shift when compared with moving targets to separate the two returns. Clutter filtering is used to remove both main-beam and altitude clutter returns, and fast moving target detection is done effectively by exploiting its Doppler frequency. In many modern pulse Doppler radars the limiting factor in detecting slow moving targets is not clutter but rather another source of noise referred to as phase noise generated from the receiver local oscillator instabilities.
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Krasnov, Oleg A., and Alexander G. Yarovoy. "Radar micro-Doppler of wind turbines: simulation and analysis using rotating linear wire structures." International Journal of Microwave and Wireless Technologies 7, no. 3-4 (June 2015): 459–67. http://dx.doi.org/10.1017/s1759078715000641.
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A simple electromagnetic model of wind-turbine's main structural elements as the linear wired structures is developed to simulate the temporal patterns of observed radar return Doppler spectra (micro-Doppler). Using the model, the micro-Doppler for different combinations of the turbines rotation frequency, radar pulse repetition frequency, and duration of the Doppler measurement interval are analyzed. The model is validated using the PARSAX radar experimental data. The model ability to reproduce the observed Doppler spectra main features can be used for development of signal-processing algorithms to suppress the wind-turbines clutter in modern Doppler radars.
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Wasserzier, Christoph. "Exploiting the Low Doppler Tolerance of Noise Radar to Perform Precise Velocity Measurements on a Short Set of Data." Signals 2, no. 1 (January 21, 2021): 25–40. http://dx.doi.org/10.3390/signals2010003.
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The extraction of velocity information from radar data by means of the Doppler effect is the driving factor for the investigations presented in this paper. A method for the quantification of the Doppler tolerance in continuous emission (CE) noise radar is introduced, addressing a current lack in literature within the frame of CE noise radars. It is shown that noise radar is highly sensitive to the Doppler effect, an issue that often results in a low Doppler tolerance especially for long coherent integration intervals. In general, the Doppler sensitivity is considered as a drawback but, in this paper, along with the absence of range-Doppler coupling in noise radar, it is turned into an advantage allowing for a very precise Doppler estimation. This new signal processing approach for Doppler extraction is detailed and its feasibility is proven on the basis of experimental data. The presented method requires much less data, i.e., target illumination time, than conventional Doppler analyses and, therefore, is beneficial in terms of radar resource management.
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Liou, Yu-Chieng, Howard B. Bluestein, Michael M. French, and Zachary B. Wienhoff. "Single-Doppler Velocity Retrieval of the Wind Field in a Tornadic Supercell Using Mobile, Phased-Array, Doppler Radar Data." Journal of Atmospheric and Oceanic Technology 35, no. 8 (August 2018): 1649–63. http://dx.doi.org/10.1175/jtech-d-18-0004.1.
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AbstractA three-dimensional data assimilation (3DVar) least squares–type single-Doppler velocity retrieval (SDVR) algorithm is utilized to retrieve the wind field of a tornadic supercell using data collected by a mobile, phased-array, Doppler radar [Mobile Weather Radar (MWR) 05XP] with very high temporal resolution (6 s). It is found that the cyclonic circulation in the hook-echo region can be successfully recovered by the SDVR algorithm. The quality of the SDVR analyses is evaluated by dual-Doppler syntheses using data collected by two mobile Doppler radars [Doppler on Wheels 6 and 7 (DOW6 and DOW7, respectively)]. A comparison between the SDVR analyses and dual-Doppler syntheses confirms the conclusion reached by an earlier theoretical analysis that because of the temporally discrete nature of the radar data, the wind speed retrieved by single-Doppler radar is always underestimated, and this underestimate occurs more significantly for the azimuthal (crossbeam) wind component than for the radial (along beam) component. However, the underestimate can be mitigated by increasing the radar data temporal resolution. When the radar data are collected at a sufficiently high rate, the azimuthal wind component may be overestimated. Even with data from a rapid scan, phased-array, Doppler radar, our study indicates that it is still necessary to calculate the SDVR in an optimal moving frame of reference. Finally, the SDVR algorithm’s robustness is demonstrated. Even with a temporal resolution (2 min) much lower than that of the phased-array radar, the cyclonic flow structure in the hook-echo region can still be retrieved through SDVR using data observed by DOW6 or DOW7, although a difference in the retrieved fields does exist. A further analysis indicates that this difference is caused by the location of the radars.
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RAO, P. RAJESH, S. KALYANA SUNDARAM, S. B. THAMPI, R. SURESH, and J. P. GUPTA. "An overview of first Doppler Weather Radar inducted in the cyclone detection network of India Meteorological Department." MAUSAM 55, no. 1 (January 19, 2022): 155–76. http://dx.doi.org/10.54302/mausam.v55i1.963.
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India Meteorological Department (IMD) maintains a wide network of radars for the detection and study of severe weather phenomena like cyclones, thunderstorms, gust front etc. and for deriving upper air wind profile. To keep pace with the fast developments in the field of weather radar technology, IMD is gradually replacing its conventional radars with digital radars, a few of them with Doppler capabilities. An S-band Doppler Weather Radar (DWR) has been inducted into India Meteorological Department’s (IMD) Cyclone Detection Radar (CDR) network recently at Chennai as a replacement to the outlived analogue S-band radar and is declared operational from 21 February 2002. Salient features, both hardware and software, of the radar are discussed in this article.
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Richter, C., H. Jeske, and G. Peters. "The Doppler radar as rain gauge." Meteorologische Zeitschrift 1, no. 5 (November 5, 1992): 229–35. http://dx.doi.org/10.1127/metz/1/1992/229.
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Dolan, Brenda A., and Steven A. Rutledge. "An Integrated Display and Analysis Methodology for Multivariable Radar Data." Journal of Applied Meteorology and Climatology 46, no. 8 (August 1, 2007): 1196–213. http://dx.doi.org/10.1175/jam2524.1.
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Abstract Polarimetric Doppler radars provide valuable information about the kinematic and microphysical structure of storms. However, in-depth analysis using radar products, such as Doppler-derived wind vectors and hydrometeor identification, has been difficult to achieve in (near) real time, mainly because of the large volumes of data generated by these radars, lack of quick access to these data, and the challenge of applying quality-control measures in real time. This study focuses on modifying and automating several radar-analysis and quality-control algorithms currently used in postprocessing and merging the resulting data from several radars into an integrated analysis and display in (near) real time. Although the method was developed for a specific network of four Doppler radars: two Weather Surveillance Radar-1988 Doppler (WSR-88D) radars (KFTG and KCYS) and two Colorado State University (CSU) research radars [Pawnee and CSU–University of Chicago–Illinois State Water Survey (CSU–CHILL)], the software is easily adaptable to any radar platform or network of radars. The software includes code to synthesize radial velocities to obtain three-dimensional wind vectors and includes algorithms for automatic quality control of the raw polarimetric data, hydrometeor identification, and rainfall rate. The software was successfully tested during the summers of 2004 and 2005 at the CSU–CHILL radar facility, ingesting data from the four-radar network. The display software allows users the ability to view mosaics of reflectivity, wind vectors, and rain rates, to zoom in and out of radar features easily, to create vertical cross sections, to contour data, and to archive data in real time. Despite the lag time of approximately 10 min, the software proved invaluable for diagnosing areas of intense rainfall, hail, strong updrafts, and other features such as mesocyclones and convergence lines. A case study is presented to demonstrate the utility of the software.
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Fujiyoshi, Yasushi, Koji Osumi, Masayuki Ohi, and Yoshinori Yamada. "Sea Ice Identification and Derivation of Its Velocity Field by X-Band Doppler Radar." Journal of Atmospheric and Oceanic Technology 30, no. 6 (June 1, 2013): 1240–49. http://dx.doi.org/10.1175/jtech-d-12-00155.1.
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Abstract In this study a 3D scanning X-band Doppler radar (XDR) was deployed near the coast of the Sea of Okhotsk, Hokkaido, Japan, in November 2005 to simultaneously observe sea ice and snow clouds. Doppler radars are commonly used to detect wind fields within precipitating clouds. However, thus far, there have been no reports of observing sea ice with Doppler radar. Making use of the radar reflectivity, Doppler velocity, and spectrum width, sea ice floes were identified under various weather conditions. Also presented is a new method that combines Doppler radar data and sea ice velocity—extracted using the cross-correlation method—to derive a high-spatial-resolution horizontal distribution of the velocity of sea ice floes. These methods will contribute to short-term forecasting of sea ice conditions and navigation through ice-covered seas and the development and verification of high-resolution dynamic sea ice models.
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Kollias, Pavlos, Mark A. Miller, Edward P. Luke, Karen L. Johnson, Eugene E. Clothiaux, Kenneth P. Moran, Kevin B. Widener, and Bruce A. Albrecht. "The Atmospheric Radiation Measurement Program Cloud Profiling Radars: Second-Generation Sampling Strategies, Processing, and Cloud Data Products." Journal of Atmospheric and Oceanic Technology 24, no. 7 (July 1, 2007): 1199–214. http://dx.doi.org/10.1175/jtech2033.1.
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Abstract The U.S. Department of Energy Atmospheric Radiation Measurement (ARM) Program operates millimeter-wavelength cloud radars in several climatologically distinct regions. The digital signal processors for these radars were recently upgraded and allow for enhancements in the operational parameters running on them. Recent evaluations of millimeter-wavelength cloud radar signal processing performance relative to the range of cloud dynamical and microphysical conditions encountered at the ARM Program sites have indicated that improvements are necessary, including significant improvement in temporal resolution (i.e., less than 1 s for dwell and 2 s for dwell and processing), wider Nyquist velocities, operational dealiasing of the recorded spectra, removal of pulse compression while sampling the boundary layer, and continuous recording of Doppler spectra. A new set of millimeter-wavelength cloud radar operational modes that incorporate these enhancements is presented. A significant change in radar sampling is the introduction of an uneven mode sequence with 50% of the sampling time dedicated to the lower atmosphere, allowing for detailed characterization of boundary layer clouds. The changes in the operational modes have a substantial impact on the postprocessing algorithms that are used to extract cloud information from the radar data. New methods for postprocessing of recorded Doppler spectra are presented that result in more accurate identification of radar clutter (e.g., insects) and extraction of turbulence and microphysical information. Results of recent studies on the error characteristics of derived Doppler moments are included so that uncertainty estimates are now included with the moments. The microscale data product based on the increased temporal resolution of the millimeter-wavelength cloud radars is described. It contains the number of local maxima in each Doppler spectrum, the Doppler moments of the primary peak, uncertainty estimates for the Doppler moments of the primary peak, Doppler moment shape parameters (e.g., skewness and kurtosis), and clear-air clutter flags.
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Lakshmanan, Valliappa, Travis Smith, Kurt Hondl, Gregory J. Stumpf, and Arthur Witt. "A Real-Time, Three-Dimensional, Rapidly Updating, Heterogeneous Radar Merger Technique for Reflectivity, Velocity, and Derived Products." Weather and Forecasting 21, no. 5 (October 1, 2006): 802–23. http://dx.doi.org/10.1175/waf942.1.
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Abstract With the advent of real-time streaming data from various radar networks, including most Weather Surveillance Radars-1988 Doppler and several Terminal Doppler Weather Radars, it is now possible to combine data in real time to form 3D multiple-radar grids. Herein, a technique for taking the base radar data (reflectivity and radial velocity) and derived products from multiple radars and combining them in real time into a rapidly updating 3D merged grid is described. An estimate of that radar product combined from all the different radars can be extracted from the 3D grid at any time. This is accomplished through a formulation that accounts for the varying radar beam geometry with range, vertical gaps between radar scans, the lack of time synchronization between radars, storm movement, varying beam resolutions between different types of radars, beam blockage due to terrain, differing radar calibration, and inaccurate time stamps on radar data. Techniques for merging scalar products like reflectivity, and innovative, real-time techniques for combining velocity and velocity-derived products are demonstrated. Precomputation techniques that can be utilized to perform the merger in real time and derived products that can be computed from these three-dimensional merger grids are described.
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Ding, Han, Haoran Li, and Liping Liu. "Improved spectral processing for a multi-mode pulse compression Ka–Ku-band cloud radar system." Atmospheric Measurement Techniques 15, no. 20 (October 26, 2022): 6181–200. http://dx.doi.org/10.5194/amt-15-6181-2022.
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Abstract. Cloud radars are widely used in observing clouds and precipitation. However, the raw data products of cloud radars are usually affected by multiple factors, which may lead to misinterpretation of cloud and precipitation processes. In this study, we present a Doppler-spectra-based data processing framework to improve the data quality of a multi-mode pulse-compressed Ka–Ku radar system. Firstly, non-meteorological signal close to the ground was identified with enhanced Doppler spectral ratios between different observing modes. Then, for the Doppler spectrum affected by the range sidelobe due to the implementation of the pulse compression technique, the characteristics of the probability density distribution of the spectral power were used to identify the sidelobe artifacts. Finally, the Doppler spectra observations from different modes were merged via the shift-then-average approach. The new radar moment products were generated based on the merged Doppler spectrum data. The presented spectral processing framework was applied to radar observations of a stratiform precipitation event, and the quantitative evaluation shows good performance of clutter or sidelobe suppression and spectral merging.
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Mohd Basir, Shafinaz, Idnin Pasya, Tajmalludin Yaakob, Nur Emileen Abd Rashid, and Takehiko Kobayashi. "Improvement of Doppler measurement using multiple-input multiple-output (MIMO) concept in radar-based automotive sensor detecting pedestrians." Sensor Review 38, no. 2 (March 19, 2018): 239–47. http://dx.doi.org/10.1108/sr-04-2017-0060.
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Purpose This paper aims to present an approach of utilizing multiple-input multiple-output (MIMO) radar concept to enhance pedestrian classification in automotive sensors. In a practical environment, radar signals reflected from pedestrians and slow-moving vehicles are similar in terms of reflecting angle and Doppler returns, inducing difficulty for target discrimination. An efficient discrimination between the two targets depends on the ability of the sensor to extract unique characteristics from each target, for example, by exploiting Doppler signatures. This study describes the utilization of MIMO radar for Doppler measurement and demonstrates its application to improve pedestrian classification through actual laboratory measurements. Design/methodology/approach Multiple non-modulated sinusoidal signals are transmitted orthogonally over a MIMO array using time division scheme, illuminating human and non-human targets. The reflected signal entering each of the receiving antenna are combined at the radar receiver prior to Doppler processing. Doppler histogram was formulated based on a series of measurements, and the Doppler spread of the targets was determined from the histograms. Results were compared between MIMO and conventional single antenna systems. Findings Measurement results indicated that the MIMO configuration provides able to capture more Doppler information compared to conventional single antenna systems, enabling a more precise discrimination between pedestrian and other slow-moving objects on the road. Originality/value The study demonstrated the effectiveness of using MIMO configuration in radar-based automotive sensor to enhance the accuracy of Doppler estimation, which is seldom highlighted in literature of MIMO radars. The result also indicated its usefulness in improving target discrimination capability of the radar, through actual measurement.
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Lipa, Barrick, and Whelan. "A Quality Control Method for Broad-Beam HF Radar Current Velocity Measurements." Journal of Marine Science and Engineering 7, no. 4 (April 19, 2019): 112. http://dx.doi.org/10.3390/jmse7040112.
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This paper describes a method to provide quality control for radial velocity maps derived from radar echo voltage cross spectra measured by broad-beam high frequency radars. The method involves the comparison of voltage cross spectra measured at Doppler frequencies in the Bragg region with values predicted from basic equations defining the complex voltage cross spectra in terms of the measured antenna patterns and the radar cross section. Poor agreement at a given Doppler frequency indicates contamination of the spectra, usually due to interference; velocity results from that Doppler frequency are then eliminated. Examples are given of its application to broad-beam radars operating at four sites.
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Rodrigues, Davi V. Q., and Changzhi Li. "A Review on Low-Cost Microwave Doppler Radar Systems for Structural Health Monitoring." Sensors 21, no. 8 (April 8, 2021): 2612. http://dx.doi.org/10.3390/s21082612.
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Portable, low-cost, microwave radars have attracted researchers’ attention for being an alternative noncontact solution for structural condition monitoring. In addition, by leveraging their capability of providing the target velocity information, the radar-based remote monitoring of complex rotating structures can also be accomplished. Modern radar systems are compact, able to be easily integrated in sensor networks, and can deliver high accuracy measurements. This paper reviews the recent technical advances in low-cost Doppler radar systems for phase-demodulated displacement measurements and time-Doppler analysis for structural health information, including digital signal processing and emerging applications related to radar sensor networks.
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Bestugin, Aleksandr R., Maksim B. Ryzhikov, Yuliana A. Novikova, and Irina A. Kirshina. "Increasing the effectiveness of aircraft detection on catch-up courses in pulse-Doppler airborne radars with a low carrier flight altitude." T-Comm 17, no. 4 (2023): 11–16. http://dx.doi.org/10.36724/2072-8735-2023-17-4-11-16.
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Problem statement. The effectiveness of solving the problem of warning about possible collisions of small aircraft or unmanned aerial vehicles intended for the development of hard-to-reach territories depends on the time of early detection of another aircraft on intersecting trajectories. As a result of the comparative analysis of radar detection methods carried out in the article, taking into account the differences in the signal-interference situation characteristic of on-board pulse−Doppler radars for targets on catch-up courses in versions "multiple input - multiple output", "with joint a posteriori processing of results" and in traditional radar with active or passive phased antenna arrays have shown that the latter have energy advantages. Therefore, for this category of pulse-Doppler radars, a method for estimating the detection range on several frames is presented, which allows you to choose the logic of operation with an increase in the detection range. Research methods. The theory of antenna arrays and the theory of radar detection for pulse-Doppler radars were actively used in the work with the specified requirements for the probabilities of correct detection, false alarm and the selected model of fluctuations of the reflected useful signal. Purpose. To substantiate the advantages of technical solutions based on a traditional technical solution with phased antenna arrays for detection on catch-up courses and to develop recommendations for finding conditions that allow to increase the detection range. Results. The simulation results are presented, showing an improvement in the conditions for radar detection in onboard pulse-Doppler radars when finding the spectrum of the reflected radar signal in the Doppler frequency range, on which the spectrum of the reflected signal from the Earth's surface is superimposed when using radar with phased antenna arrays compared with spatial processing methods in MIMO and radars with joint a posteriori processing of results. A method for calculating the detection range on several adjacent frames has been developed and it is shown that in this case a longer range is achieved compared to the case of detection on a single frame. Practical significance. The results of the work can be used in small-sized onboard pulse radars of low-altitude carriers in order to increase the time of early warning of the presence of other aircraft on the flight path. This task seems to be especially relevant when flying radar carriers in hard-to-reach, developed territories.
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Wang, Wen-Qin. "Detecting and Mitigating Wind Turbine Clutter for Airspace Radar Systems." Scientific World Journal 2013 (2013): 1–8. http://dx.doi.org/10.1155/2013/385182.
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It is well recognized that a wind turbine has a large radar cross-section (RCS) and, due to the movement of the blades, the wind turbine will generate a Doppler frequency shift. This scattering behavior may cause severe interferences on existing radar systems including static ground-based radars and spaceborne or airborne radars. To resolve this problem, efficient techniques or algorithms should be developed to mitigate the effects of wind farms on radars. Herein, one transponder-based mitigation technique is presented. The transponder is not a new concept, which has been proposed for calibrating high-resolution imaging radars. It modulates the radar signal in a manner that the retransmitted signals can be separated from the scene echoes. As wind farms often occupy only a small area, mitigation processing in the whole radar operation will be redundant and cost inefficient. Hence, this paper uses a transponder to determine whether the radar is impacted by the wind farms. If so, the effects of wind farms are then mitigated with subsequent Kalman filtering or plot target extraction algorithms. Taking airborne synthetic aperture radar (SAR) and pulse Doppler radar as the examples, this paper provides the corresponding system configuration and processing algorithms. The effectiveness of the mitigation technique is validated by numerical simulation results.
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Vivekanandan, J., W. C. Lee, E. Loew, J. L. Salazar, V. Grubišić, J. Moore, and P. Tsai. "The next generation airborne polarimetric Doppler weather radar." Geoscientific Instrumentation, Methods and Data Systems Discussions 4, no. 1 (January 20, 2014): 1–42. http://dx.doi.org/10.5194/gid-4-1-2014.
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Abstract. Results from airborne field deployments emphasized the need to obtain concurrently high temporal and spatial resolution measurements of 3-D winds and microphysics. A phased array radar on an airborne platform using dual-polarization antenna has the potential for retrieving high resolution, collocated 3-D winds and microphysical measurements. Recently, ground-based phased array radar (PAR) demonstrated the high time resolution estimation of accurate Doppler velocity and reflectivity of precipitation and clouds when compared to mechanically scanning radar. PAR uses the electronic scanning (e-scan) to rapidly collect radar measurements. Since an airborne radar has a limited amount of time to collect measurements over a specified sample volume, the e-scan will significantly enhance temporal and spatial resolution of airborne radar observations. At present, airborne weather radars use mechanical scan, and they are not designed for collecting dual-polarization measurements to remotely estimate microphysics. This paper presents a possible configuration of a novel Airborne Phased Array Radar (APAR) to be installed on an aircraft for retrieving improved dynamical and microphysical scientific products. The proposed APAR would replace the aging, X-band Electra Doppler radar (ELDORA). The ELDORA X-band radar's penetration into precipitation is limited by attenuation. Since attenuation at C-band is lower than at X-band, the design specification of a C-band airborne phased array radar (APAR) and its measurement accuracies are presented.
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Kollias, Pavlos, Simone Tanelli, Alessandro Battaglia, and Aleksandra Tatarevic. "Evaluation of EarthCARE Cloud Profiling Radar Doppler Velocity Measurements in Particle Sedimentation Regimes." Journal of Atmospheric and Oceanic Technology 31, no. 2 (February 1, 2014): 366–86. http://dx.doi.org/10.1175/jtech-d-11-00202.1.
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Abstract The joint European Space Agency–Japan Aerospace Exploration Agency (ESA–JAXA) Earth Clouds, Aerosols and Radiation Explorer (EarthCARE) mission is scheduled for launch in 2016 and features the first atmospheric Cloud Profiling Radar (CPR) with Doppler capability in space. Here, the uncertainty of the CPR Doppler velocity measurements in cirrus clouds and large-scale precipitation areas is discussed. These regimes are characterized by weak vertical motion and relatively horizontally homogeneous conditions and thus represent optimum conditions for acquiring high-quality CPR Doppler measurements. A large dataset of radar reflectivity observations from ground-based radars is used to examine the homogeneity of the cloud fields at the horizontal scales of interest. In addition, a CPR instrument model that uses as input ground-based radar observations and outputs simulations of CPR Doppler measurements is described. The simulator accurately accounts for the beam geometry, nonuniform beam-filling, and signal integration effects, and it is applied to representative cases of cirrus cloud and stratiform precipitation. The simulated CPR Doppler velocities are compared against those derived from the ground-based radars. The unfolding of the CPR Doppler velocity is achieved using simple conditional rules and a smoothness requirement for the CPR Doppler measurements. The application of nonuniform beam-filling Doppler velocity bias-correction algorithms is found necessary even under these optimum conditions to reduce the CPR Doppler biases. Finally, the analysis indicates that a minimum along-track integration of 5000 m is needed to reduce the uncertainty in the CPR Doppler measurements to below 0.5 m s−1 and thus enable the detection of the melting layer and the characterization of the rain- and ice-layer Doppler velocities.
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Garcia-Benadí, Albert, Joan Bech, Sergi Gonzalez, Mireia Udina, and Bernat Codina. "A New Methodology to Characterise the Radar Bright Band Using Doppler Spectral Moments from Vertically Pointing Radar Observations." Remote Sensing 13, no. 21 (October 27, 2021): 4323. http://dx.doi.org/10.3390/rs13214323.
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The detection and characterisation of the radar Bright Band (BB) are essential for many applications of weather radar quantitative precipitation estimates, such as heavy rainfall surveillance, hydrological modelling or numerical weather prediction data assimilation. This study presents a new technique to detect the radar BB levels (top, peak and bottom) for Doppler radar spectral moments from the vertically pointing radars applied here to a K-band radar, the MRR-Pro (Micro Rain Radar). The methodology includes signal and noise detection and dealiasing schemes to provide realistic vertical Doppler velocities of precipitating hydrometeors, subsequent calculation of Doppler moments and associated parameters and BB detection and characterisation. Retrieved BB properties are compared with the melting level provided by the MRR-Pro manufacturer software and also with the 0 °C levels for both dry-bulb temperature (freezing level) and wet-bulb temperature from co-located radio soundings in 39 days. In addition, a co-located Parsivel disdrometer is used to analyse the equivalent reflectivity of the lowest radar height bins confirming consistent results of the new signal and noise detection scheme. The processing methodology is coded in a Python program called RaProM-Pro which is freely available in the GitHub repository.
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Gergely, Mathias, Maximilian Schaper, Matthias Toussaint, and Michael Frech. "Doppler spectra from DWD's operational C-band radar birdbath scan: sampling strategy, spectral postprocessing, and multimodal analysis for the retrieval of precipitation processes." Atmospheric Measurement Techniques 15, no. 24 (December 20, 2022): 7315–35. http://dx.doi.org/10.5194/amt-15-7315-2022.
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Abstract. This study explores the potential of using Doppler (power) spectra from vertically pointing C-band radar birdbath scans to investigate precipitating clouds above the radar. First, the new birdbath scan strategy for the network of dual-polarization C-band radars operated by the German Meteorological Service (Deutscher Wetterdienst, DWD) is outlined, and a novel spectral postprocessing and analysis method is presented. The postprocessing algorithm isolates the weather signal from non-meteorological contributions in the radar output based on polarimetric attributes, identifies the statistically significant precipitation modes contained in each Doppler spectrum, and calculates characteristics of every precipitation mode as well as multimodal properties that describe the relation among different modes when more than a single mode is identified. To achieve a high degree of automation and flexibility, the postprocessing chain combines classical signal processing with clustering algorithms. Uncertainties in the calculated modal and multimodal properties are estimated from the small variations associated with smoothing the measured radar signal. The analysis of five birdbath scans recorded at different radar sites and for various precipitation conditions delivers reliable profiles of the derived modal and multimodal properties for two snowfall cases and for stratiform precipitation above and below the melting layer. To help identify the dominant precipitation growth mechanism, Doppler spectra from DWD's birdbath scans can be used to retrieve the typical degree of riming for individual snow modes. Here, the automatically identified snow modes span a wide range of riming conditions with estimated rime mass fractions (RMFs) of up to RMF>0.5. The evaluation of Doppler spectra inside the melting layer and for an intense frontal shower, with observed radar reflectivities of up to about 40 dBZ, occasionally shows erroneously identified precipitation modes and spurious results for the calculated higher-order Doppler moments of skewness and kurtosis. Nonetheless, the Doppler spectra from DWD's operational C-band radar birdbath scan provide a detailed view into the precipitating clouds and allow for calculating a high-resolution profile of radar reflectivity, mean Doppler velocity, and spectral width even in intense frontal precipitation.
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Bailey, Brandon M., Torrey J. Wagner, and Jada B. Williams. "E700XD Portable Doppler Radar Energy Systems Analysis." International Journal of Electrical Energy 7, no. 2 (December 2019): 62–66. http://dx.doi.org/10.18178/ijoee.7.2.62-66.
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Greenwald, Raymond A. "History of the Super Dual Auroral Radar Network (SuperDARN)-I: pre-SuperDARN developments in high frequency radar technology for ionospheric research and selected scientific results." History of Geo- and Space Sciences 12, no. 1 (May 11, 2021): 77–93. http://dx.doi.org/10.5194/hgss-12-77-2021.
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Abstract. Part I of this history describes the motivations for developing radars in the high frequency (HF) band to study plasma density irregularities in the F region of the auroral zone and polar cap ionospheres. French and Swedish scientists were the first to use HF frequencies to study the Doppler velocities of HF radar backscatter from F-region plasma density irregularities over northern Sweden. These observations encouraged the author of this paper to pursue similar measurements over northeastern Alaska, and this eventually led to the construction of a large HF-phased-array radar at Goose Bay, Labrador, Canada. This radar utilized frequencies from 8–20 MHz and could be electronically steered over 16 beam directions, covering a 52∘ azimuth sector. Subsequently, similar radars were constructed at Schefferville, Quebec, and Halley Station, Antarctica. Observations with these radars showed that F-region backscatter often exhibited Doppler velocities that were significantly above and below the ion-acoustic velocity. This distinguished HF Doppler measurements from prior measurements of E-region irregularities that were obtained with radars operating at very high frequency (VHF) and ultra-high frequency (UHF). Results obtained with these early HF radars are also presented. They include comparisons of Doppler velocities observed with HF radars and incoherent scatter radars, comparisons of plasma convection patterns observed simultaneously in conjugate hemispheres, and the response of these patterns to changes in the interplanetary magnetic field, transient velocity enhancements in the dayside cusp, preferred frequencies for geomagnetic pulsations, and observations of medium-scale atmospheric gravity waves with HF radars.
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Goh, Y. K., A. R. Holt, and P. P. Alberoni. "Doppler radar wind field retrieval over the Po Valley." Natural Hazards and Earth System Sciences 6, no. 2 (May 4, 2006): 285–91. http://dx.doi.org/10.5194/nhess-6-285-2006.
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Abstract. Although methods of using multiple Doppler radars to study wind fields have long been proposed, and many research studies have been made, very few operational radar operators adopt methods which require the use of specific scanning strategies to allow the extraction of wind information. Here we report a collaborative study on dual-Doppler radars based on two Doppler radars in the Po valley, Italy. Unusually, the radars are only about 90 km apart, though operated by the same authority. The wind field syntheses are carried out on a 30 km by 30 km region where the two radars have overlapping scan coverage. An iterative method based on the linear wind model and the equation of mass continuity is used to construct the wind fields. The methodology has been validated by two different methods. The first method is to reconstruct the radial wind observed by each radar, and the second method is calculating and comparing the along-track component with that derived from the observations. Both two comparisons show good agreement with the original data.
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He, Yuan, Pascal Aubry, Francois Le Chevalier, and Alexander Yarovoy. "Self-similarity matrix based slow-time feature extraction for human target in high-resolution radar." International Journal of Microwave and Wireless Technologies 6, no. 3-4 (March 25, 2014): 423–34. http://dx.doi.org/10.1017/s1759078714000087.
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A new approach is proposed to extract the slow-time feature of human motion in high-resolution radars. The approach is based on the self-similarity matrix (SSM) of the radar signals. The Mutual Information is used as a measure of similarity. The SSMs of different radar signals (high-resolution range profile, micro-Doppler, and range-Doppler video sequence) are compared, and the angel-invariant property of the SSMs is demonstrated. The SSM for different activities (i.e. walking and running) is extracted from range-Doppler video sequence and analyzed. Finally, simulation result is validated by experimental data.
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Johnston, Paul E., James R. Jordan, Allen B. White, David A. Carter, David M. Costa, and Thomas E. Ayers. "The NOAA FM-CW Snow-Level Radar." Journal of Atmospheric and Oceanic Technology 34, no. 2 (February 2017): 249–67. http://dx.doi.org/10.1175/jtech-d-16-0063.1.
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AbstractA vertically pointing radar for monitoring radar brightband height (BBH) has been developed. This new radar utilizes frequency-modulated continuous wave (FM-CW) techniques to provide high-resolution data at a fraction of the cost of comparable pulsed radars. This S-band radar provides details of the vertical structure of precipitating clouds, with full Doppler information. Details of the radar design are presented along with observations from one storm. Results from a calibration using these storm data show the radar meets the design goals. Eleven of these radars have been deployed and provide BBH data in near–real time.
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Seflek, Ibrahim, Yunus Emre Acar, and Ercan Yaldiz. "Small Motion Detection and Non-Contact Vital Signs Monitoring with Continuous Wave Doppler Radars." Elektronika ir Elektrotechnika 26, no. 3 (June 27, 2020): 54–60. http://dx.doi.org/10.5755/j01.eie.26.3.25810.
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Radars have become devices that one can come across in any environment at any moment. This means that they enter to all areas of life and even in the field of medicine and will be used more intensively in the future. Especially, the attention has been drawn to that they are suitable for the non-contact vital signs monitoring. In this study, two radar structures operating at 24 GHz (Radar 1) and 2.4 GHz (Radar 2) frequencies are used. Radar 1 structure is created on a printed circuit board (PCB), whereas Radar 2 is obtained by combining discrete components. The 8.5 mm movement performed with the aid of a test mechanism is detected by two radars with percentage errors (PEs) of 2.58% and 6.23%, respectively. For the 0.25 Hz vibration frequency, the error is the same for both radars and is 2.4 %. In measurements taken from a healthy human subject, Radar 1 finds a respiration rate with 1.85 % of PE and heart beat rate with 6.17 % of PE. In Radar 2, these values are 2.35 % and 8.24 %, respectively. From the measurement results, it is seen that the resolution of Radar 1 is better than that of Radar 2. The results also indicate that small motion detection and vital signs monitoring are carried out successfully.
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Spargo, Andrew J., Iain M. Reid, Andrew D. MacKinnon, and David A. Holdsworth. "Mesospheric gravity wave momentum flux estimation using hybrid Doppler interferometry." Annales Geophysicae 35, no. 3 (June 12, 2017): 733–50. http://dx.doi.org/10.5194/angeo-35-733-2017.
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Abstract. Mesospheric gravity wave (GW) momentum flux estimates using data from multibeam Buckland Park MF radar (34.6° S, 138.5° E) experiments (conducted from July 1997 to June 1998) are presented. On transmission, five Doppler beams were symmetrically steered about the zenith (one zenith beam and four off-zenith beams in the cardinal directions). The received beams were analysed with hybrid Doppler interferometry (HDI) (Holdsworth and Reid, 1998), principally to determine the radial velocities of the effective scattering centres illuminated by the radar. The methodology of Thorsen et al. (1997), later re-introduced by Hocking (2005) and since extensively applied to meteor radar returns, was used to estimate components of Reynolds stress due to propagating GWs and/or turbulence in the radar resolution volume. Physically reasonable momentum flux estimates are derived from the Reynolds stress components, which are also verified using a simple radar model incorporating GW-induced wind perturbations. On the basis of these results, we recommend the intercomparison of momentum flux estimates between co-located meteor radars and vertical-beam interferometric MF radars. It is envisaged that such intercomparisons will assist with the clarification of recent concerns (e.g. Vincent et al., 2010) of the accuracy of the meteor radar technique.
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Griffin, Casey B., David J. Bodine, and Robert D. Palmer. "Kinematic and Polarimetric Radar Observations of the 10 May 2010, Moore–Choctaw, Oklahoma, Tornadic Debris Signature." Monthly Weather Review 145, no. 7 (July 2017): 2723–41. http://dx.doi.org/10.1175/mwr-d-16-0344.1.
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Tornadoes are capable of lofting large pieces of debris that present irregular shapes, near-random orientations, and a wide range of dielectric constants to polarimetric radars. The unique polarimetric signature associated with lofted debris is called the tornadic debris signature (TDS). While ties between TDS characteristics and tornado- and storm-scale kinematic processes have been speculated upon or investigated using photogrammetry and single-Doppler analyses, little work has been done to document the three-dimensional wind field associated with the TDS. Data collected by the Oklahoma City, Oklahoma (KTLX), and Norman, Oklahoma (KOUN), WSR-88D S-band radars as well as the University of Oklahoma’s (OU) Advanced Radar Research Center’s Polarimetric Radar for Innovations in Meteorology and Engineering (OU-PRIME) C-band radar are used to construct single- and dual-Doppler analyses of a tornadic supercell that produced an EF4 tornado near the towns of Moore and Choctaw, Oklahoma, on 10 May 2010. This study documents the spatial distribution of polarimetric radar variables and how each variable relates to kinematic fields such as vertical velocity and vertical vorticity. Special consideration is given to polarimetric signatures associated with subvortices within the tornado. An observation of negative differential reflectivity ([Formula: see text]) at the periphery of tornado subvortices is presented and discussed. Finally, dual-Doppler wind retrievals are compared to single-Doppler axisymmetric wind fields to illustrate the merits of each method.
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Vivekanandan, J., W. C. Lee, E. Loew, J. L. Salazar, V. Grubišić, J. Moore, and P. Tsai. "The next generation airborne polarimetric Doppler weather radar." Geoscientific Instrumentation, Methods and Data Systems 3, no. 2 (July 21, 2014): 111–26. http://dx.doi.org/10.5194/gi-3-111-2014.
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Abstract. Results from airborne field deployments emphasized the need to obtain concurrently high temporal and spatial resolution measurements of 3-D winds and microphysics. A phased array radar on an airborne platform using dual-polarization antenna has the potential for retrieving high-resolution, collocated 3-D winds and microphysical measurements. Recently, ground-based phased array radar (PAR) has demonstrated the high time-resolution estimation of accurate Doppler velocity and reflectivity of precipitation and clouds when compared to mechanically scanning radar. PAR uses the electronic scanning (e-scan) to rapidly collect radar measurements. Since an airborne radar has a limited amount of time to collect measurements over a specified sample volume, the e-scan will significantly enhance temporal and spatial resolution of airborne radar observations. At present, airborne weather radars use mechanical scans, and they are not designed for collecting dual-polarization measurements to remotely estimate microphysics. This paper presents a possible configuration of a novel airborne phased array radar (APAR) to be installed on an aircraft for retrieving improved dynamical and microphysical scientific products. The proposed APAR would replace the aging, X-band Electra Doppler radar (ELDORA). The ELDORA X-band radar's penetration into precipitation is limited by attenuation. Since attenuation at C-band is lower than at X-band, the design specification of a C-band airborne phased array radar (APAR) and its measurement accuracies are presented. Preliminary design specifications suggest the proposed APAR will meet or exceed ELDORA's current sensitivity, spatial resolution and Doppler measurement accuracies of ELDORA and it will also acquire dual-polarization measurements.
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Snyder, Jeffrey C., and Alexander V. Ryzhkov. "Automated Detection of Polarimetric Tornadic Debris Signatures Using a Hydrometeor Classification Algorithm." Journal of Applied Meteorology and Climatology 54, no. 9 (September 2015): 1861–70. http://dx.doi.org/10.1175/jamc-d-15-0138.1.
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AbstractAlthough radial velocity data from Doppler radars can partially resolve some tornadoes, particularly large tornadoes near the radar, most tornadoes are not explicitly resolved by radar owing to inadequate spatiotemporal resolution. In addition, it can be difficult to determine which mesocyclones typically observed on radar are associated with tornadoes. Since debris lofted by tornadoes has scattering characteristics that are distinct from those of hydrometeors, the additional information provided by polarimetric weather radars can aid in identifying debris from tornadoes; the polarimetric tornadic debris signature (TDS) provides what is nearly “ground truth” that a tornado is ongoing (or has recently occurred). This paper outlines a modification to the hydrometeor classification algorithm used with the operational Weather Surveillance Radar-1988 Doppler (WSR-88D) network in the United States to include a TDS category. Examples of automated TDS classification are provided for several recent cases that were observed in the United States.
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Ogawa, T. "Radar observations of ionospheric irregularities at Syowa Station, Antarctica: a brief overview." Annales Geophysicae 14, no. 12 (December 31, 1996): 1454–61. http://dx.doi.org/10.1007/s00585-996-1454-z.
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Abstract. We briefly overview the radar observations that have been made for 30 years at Syowa Station, Antarctica for studying small-scale electron-density irregularities in the southern high-latitude E- and F-region ionosphere. Some observational results (i.e., long-term variations of radio aurora, Doppler spectra with narrow spectral widths and low Doppler velocities, and simultaneous observations of radar and optical auroras) from VHF radars capable of detecting 1.3- to 3-m scale irregularities are presented. A new 50-MHz radar system equipped with phased-antenna arrays began operation in February 1995 to observe two-dimensional behaviours of E-region irregularities. An HF radar experiment also began in February 1995 to explore decameter-scale E- and F-region irregularities in the auroral zone and polar cap. These two radars will contribute to a better understanding of the ionospheric irregularities and ionospheric physics at southern high latitudes.
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Oue, Mariko, Pavlos Kollias, Alan Shapiro, Aleksandra Tatarevic, and Toshihisa Matsui. "Investigation of observational error sources in multi-Doppler-radar three-dimensional variational vertical air motion retrievals." Atmospheric Measurement Techniques 12, no. 3 (March 29, 2019): 1999–2018. http://dx.doi.org/10.5194/amt-12-1999-2019.
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Abstract. Multi-Doppler-radar network observations have been used in different configurations over the last several decades to conduct three-dimensional wind retrievals in mesoscale convective systems. Here, the impacts of the selected radar volume coverage pattern (VCP), the sampling time for the VCP, the number of radars used, and the added value of advection correction on the retrieval of the vertical air motion in the upper part of convective clouds are examined using the Weather Research and Forecasting (WRF) model simulation, the Cloud Resolving Model Radar SIMulator (CR-SIM), and a three-dimensional variational multi-Doppler-radar retrieval technique. Comparisons between the model truth (i.e., WRF kinematic fields) and updraft properties (updraft fraction, updraft magnitude, and mass flux) retrieved from the CR-SIM-generated multi-Doppler-radar field are used to investigate these impacts. The findings are that (1) the VCP elevation strategy and sampling time have a significant effect on the retrieved updraft properties above 6 km in altitude; (2) 2 min or shorter VCPs have small impacts on the retrievals, and the errors are comparable to retrievals using a snapshot cloud field; (3) increasing the density of elevation angles in the VCP appears to be more effective to reduce the uncertainty than an addition of data from one more radar, if the VCP is performed in 2 min; and (4) the use of dense elevation angles combined with an advection correction applied to the 2 min VCPs can effectively improve the updraft retrievals, but for longer VCP sampling periods (5 min) the value of advection correction is challenging. This study highlights several limiting factors in the retrieval of upper-level vertical velocity from multi-Doppler-radar networks and suggests that the use of rapid-scan radars can substantially improve the quality of wind retrievals if conducted in a limited spatial domain.
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Luke, Edward P., and Pavlos Kollias. "Separating Cloud and Drizzle Radar Moments during Precipitation Onset Using Doppler Spectra." Journal of Atmospheric and Oceanic Technology 30, no. 8 (August 1, 2013): 1656–71. http://dx.doi.org/10.1175/jtech-d-11-00195.1.
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Abstract The retrieval of cloud, drizzle, and turbulence parameters using radar Doppler spectra is challenged by the convolution of microphysical and dynamical influences and the overall uncertainty introduced by turbulence. A new technique that utilizes recorded radar Doppler spectra from profiling cloud radars is presented here. The technique applies to areas in clouds where drizzle is initially produced by the autoconversion process and is detected by a positive skewness in the radar Doppler spectrum. Using the Gaussian-shape property of cloud Doppler spectra, the cloud-only radar Doppler spectrum is estimated and used to separate the cloud and drizzle contributions. Once separated, the cloud spectral peak can be used to retrieve vertical air motion and eddy dissipation rates, while the drizzle peak can be used to estimate the three radar moments of the drizzle particle size distribution. The technique works for nearly 50% of spectra found near cloud top, with efficacy diminishing to roughly 15% of spectra near cloud base. The approach has been tested on a large dataset collected in the Azores during the Atmospheric Radiation Measurement Program (ARM) Mobile Facility deployment on Graciosa Island from May 2009 through December 2010. Validation of the proposed technique is achieved using the cloud base as a natural boundary between radar Doppler spectra with and without cloud droplets. The retrieval algorithm has the potential to characterize the dynamical and microphysical conditions at cloud scale during the transition from cloud to precipitation. This has significant implications for improving the understanding of drizzle onset in liquid clouds and for improving model parameterization schemes of autoconversion of cloud water into drizzle.
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Maahn, Maximilian, Fabian Hoffmann, Matthew D. Shupe, Gijs de Boer, Sergey Y. Matrosov, and Edward P. Luke. "Can liquid cloud microphysical processes be used for vertically pointing cloud radar calibration?" Atmospheric Measurement Techniques 12, no. 6 (June 13, 2019): 3151–71. http://dx.doi.org/10.5194/amt-12-3151-2019.
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Abstract. Cloud radars are unique instruments for observing cloud processes, but uncertainties in radar calibration have frequently limited data quality. Thus far, no single robust method exists for assessing the calibration of past cloud radar data sets. Here, we investigate whether observations of microphysical processes in liquid clouds such as the transition of cloud droplets to drizzle drops can be used to calibrate cloud radars. Specifically, we study the relationships between the radar reflectivity factor and three variables not affected by absolute radar calibration: the skewness of the radar Doppler spectrum (γ), the radar mean Doppler velocity (W), and the liquid water path (LWP). For each relation, we evaluate the potential for radar calibration. For γ and W, we use box model simulations to determine typical radar reflectivity values for reference points. We apply the new methods to observations at the Atmospheric Radiation Measurement (ARM) sites North Slope of Alaska (NSA) and Oliktok Point (OLI) in 2016 using two 35 GHz Ka-band ARM Zenith Radars (KAZR). For periods with a sufficient number of liquid cloud observations, we find that liquid cloud processes are robust enough for cloud radar calibration, with the LWP-based method performing best. We estimate that, in 2016, the radar reflectivity at NSA was about 1±1 dB too low but stable. For OLI, we identify serious problems with maintaining an accurate calibration including a sudden decrease of 5 to 7 dB in June 2016.
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Mahale, Vivek N., Jerald A. Brotzge, and Howard B. Bluestein. "The Advantages of a Mixed-Band Radar Network for Severe Weather Operations: A Case Study of 13 May 2009." Weather and Forecasting 29, no. 1 (February 1, 2014): 78–98. http://dx.doi.org/10.1175/waf-d-13-00024.1.
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Abstract Adding a mix of X- or C-band radars to the current Weather Surveillance Radar-1988 Doppler (WSR-88D) network could address several limitations of the network, including improvements to spatial gaps in low-level coverage and temporal sampling of volume scans. These limitations can result in missing critical information in highly dynamic events, such as tornadoes and severe straight-line wind episodes. To evaluate the potential value of a mixed-band radar network for severe weather operations, a case study is examined using data from X- and S-band radars. On 13 May 2009, a thunderstorm complex associated with a cold front moved southward into southwest Oklahoma. A tornado rapidly developed from an embedded supercell within the complex. The life cycle of the tornado and subsequent wind event was sampled by the experimental Collaborative Adaptive Sensing of the Atmosphere (CASA) radar testbed of four X-band radars as well as two operational WSR-88Ds. In this study, the advantages of a mixed-band radar network are demonstrated through a chronological analysis of the event. The two radar networks provided enhanced overall situational awareness. Data from the WSR-88Ds provided 1) clear-air sensitivity, 2) a broad overview of the storm complex, 3) a large maximum unambiguous range, and 4) upper-level scans up to 19.5°. Data from the CASA radars provided 1) high-temporal, 1-min updates; 2) overlapping coverage for dual-Doppler analysis; and 3) dense low-level coverage. The combined system allowed for detailed, dual- and single-Doppler observations of a wind surge, a mesocyclone contraction, and a downburst.
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Wienhoff, Zachary B., Howard B. Bluestein, Louis J. Wicker, Jeffrey C. Snyder, Alan Shapiro, Corey K. Potvin, Jana B. Houser, and Dylan W. Reif. "Applications of a Spatially Variable Advection Correction Technique for Temporal Correction of Dual-Doppler Analyses of Tornadic Supercells." Monthly Weather Review 146, no. 9 (August 24, 2018): 2949–71. http://dx.doi.org/10.1175/mwr-d-17-0360.1.
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Abstract In many instances, synchronization of Doppler radar data among multiple platforms for multiple-Doppler analysis is challenging. This study describes the production of dual-Doppler wind analyses from several case studies using data from a rapid-scanning, X-band, polarimetric, Doppler radar—the RaXPol radar—and data from nearby WSR-88Ds. Of particular interest is mitigating difficulties related to the drastic differences in scanning rates of the two radars. To account for differences in temporal resolution, a variational reflectivity tracking scheme [a spatially variable advection correction technique (SVAC)] has been employed to interpolate (in a Lagrangian sense) the coarser temporal resolution data (WSR-88D) to the times of the RaXPol volume scans. The RaXPol data and temporally interpolated WSR-88D data are then used to create quasi–rapid scan dual-Doppler analyses. This study focuses on the application of the SVAC technique to WSR-88D data to create dual-Doppler analyses of three tornadic supercells: the 19 May 2013 Edmond–Carney and Norman–Shawnee, Oklahoma, storms and the 24 May 2016 Dodge City, Kansas, storm. Results of the dual-Doppler analyses are briefly examined, including observations of the ZDR columns as a proxy for updrafts. Potential improvements to this technique are also discussed.
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French, Michael M., Howard B. Bluestein, Ivan PopStefanija, Chad A. Baldi, and Robert T. Bluth. "Reexamining the Vertical Development of Tornadic Vortex Signatures in Supercells." Monthly Weather Review 141, no. 12 (November 25, 2013): 4576–601. http://dx.doi.org/10.1175/mwr-d-12-00315.1.
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Abstract Observations from a hybrid phased-array Doppler radar, the Mobile Weather Radar, 2005 X-band, Phased Array (MWR-05XP), were used to investigate the vertical development of tornadic vortex signatures (TVSs) during supercell tornadogenesis. Data with volumetric update times of ∼10 s, an order of magnitude better than that of most other mobile Doppler radars, were obtained up to storm midlevels during the formation of three tornadoes. It is found that TVSs formed upward with time during tornadogenesis for two cases. In a third case, missing low-level data prevented a complete time–height analysis of TVS development; however, TVS formation occurred first near the ground and then at storm midlevels several minutes later. These results are consistent with the small number of volumetric mobile Doppler radar tornadogenesis cases from the past ∼10 years, but counter to studies prior to that, in which a descending TVS was observed in roughly half of tornado cases utilizing Weather Surveillance Radar-1988 Doppler (WSR-88D) data. A comparative example is used to examine the possible effects relatively long WSR-88D volumetric update times have on determining the mode of tornadogenesis.
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Schutgens, N. A. J. "Simulating Range Oversampled Doppler Radar Profiles of Inhomogeneous Targets." Journal of Atmospheric and Oceanic Technology 25, no. 9 (September 1, 2008): 1514–28. http://dx.doi.org/10.1175/2007jtecha1026.1.
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Abstract A new technique for generating range oversampled profiles of Doppler radar signals that have been backscattered by distributed targets is presented in this paper. The technique was developed for spaceborne cloud radars, but it can just as well be used for ground-based precipitation or wind-profiling radars. The technique is more versatile than the traditional inverse FFT technique and faster than the individual hydrometeor simulation (Monte Carlo) technique. Doppler radar signals from backscattering hydrometeors are essentially correlated stochastic variables. The technique uses an accurate description of covariances between voltages measured for different pulses and at different positions (range gates) along a profile. A matrix formalism is developed to subsequently transform uncorrelated Gaussian noise into correlated receiver voltages with the appropriate covariances. In particular, the new technique deals with target variability in a physically consistent manner, accounting for the effects of inhomogeneity both within the instantaneous field of view and between subsequent pulses. The new technique is showcased with examples of simulated 95-GHz Doppler radar observations by the Earth Clouds, Aerosols and Radiation Explorer (EarthCARE) space mission.
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Delanoë, Julien, Alain Protat, Jean-Paul Vinson, Williams Brett, Christophe Caudoux, Fabrice Bertrand, Jacques Parent du Chatelet, et al. "BASTA: A 95-GHz FMCW Doppler Radar for Cloud and Fog Studies." Journal of Atmospheric and Oceanic Technology 33, no. 5 (May 2016): 1023–38. http://dx.doi.org/10.1175/jtech-d-15-0104.1.
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AbstractDoppler cloud radars are amazing tools to characterize cloud and fog properties and to improve their representation in models. However, commercially available cloud radars (35 and 95 GHz) are still very expensive, which hinders their widespread deployment. This study presents the development of a lower-cost semioperational 95-GHz Doppler cloud radar called the Bistatic Radar System for Atmospheric Studies (BASTA). To drastically reduce the cost of the instrument, a different approach is used compared to traditional pulsed radars: instead of transmitting a large amount of energy for a very short time period (as a pulse), a lower amount of energy is transmitted continuously. By using a specific signal processing technique, the radar can challenge expensive radars and provide high-quality measurements of cloud and fog. The latest version of the instrument has a sensitivity of about −50 dBZ at 1 km for 3-s integration and a vertical resolution of 25 m. The BASTA radar currently uses four successive modes for specific applications: the 12.5-m vertical resolution mode is dedicated to fog and low clouds, the 25-m mode is for liquid and ice midtropospheric clouds, and the 100- and 200-m modes are ideal for optically thin high-level ice clouds. The advantages of such a radar for calibration procedures and field operations are also highlighted. The radar comes with a set of products dedicated to cloud and fog studies. For instance, cloud mask, corrected Doppler velocity, and multimode products combining the high-sensitivity mode and high-resolution modes are provided.
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Giroto de Oliveira, Lucas, Theresa Antes, Benjamin Nuss, Elizabeth Bekker, Akanksha Bhutani, Axel Diewald, Mohamad Basim Alabd, Yueheng Li, Mario Pauli, and Thomas Zwick. "Doppler Shift Tolerance of Typical Pseudorandom Binary Sequences in PMCW Radar." Sensors 22, no. 9 (April 22, 2022): 3212. http://dx.doi.org/10.3390/s22093212.
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In the context of all-digital radar systems, phase-modulated continuous wave (PMCW) based on pseudorandom binary sequences (PRBSs) appears to be a prominent candidate modulation scheme for applications such as autonomous driving. Among the reasons for its candidacy are its simplified transmitter architecture and lower linearity requirements (e.g., compared to orthogonal-frequency division multiplexing radars), as well as its high velocity unambiguity and multiple-input multiple-output operation capability, all of which are characteristic of digital radars. For appropriate operation of a PMCW radar, choosing a PRBS whose periodic autocorrelation function (PACF) has low sidelobes and high robustness to Doppler shifts is paramount. In this sense, this article performs an analysis of Doppler shift tolerance of the PACFs of typically adopted PRBSs in PMCW radar systems supported by simulation and measurement results. To accurately measure the Doppler-shift-induced degradation of PACFs, peak power loss ratio (PPLR), peak sidelobe level ratio (PSLR), and integrated-sidelobe level ratio (ISLR) were used as metrics. Furthermore, to account for effects on targets whose ranges are not multiples of the range resolution, oversampled PACFs are analyzed.
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Yi, Htet Htet, and Ei Phyu Soe. "X Band Doppler Radar." International Journal of Scientific and Research Publications (IJSRP) 9, no. 7 (July 18, 2019): p91102. http://dx.doi.org/10.29322/ijsrp.9.07.2019.p91102.
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Anonymous. "New airborne Doppler radar." Eos, Transactions American Geophysical Union 71, no. 9 (1990): 301. http://dx.doi.org/10.1029/eo071i009p00301-03.
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Fernandez, J. R. O., C. Briso-Rodriguez, J. Calvo-Gallego, M. Burgos-Garcia, F. Perez-Martinez, and V. A. Arana-Pulido. "Doppler radar calibration system." IEEE Aerospace and Electronic Systems Magazine 27, no. 7 (July 2012): 20–28. http://dx.doi.org/10.1109/maes.2012.6328838.
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Belville, James D. "Polarimetric Doppler Weather Radar." Eos, Transactions American Geophysical Union 83, no. 23 (2002): 259. http://dx.doi.org/10.1029/2002eo000184.
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Battaglia, Alessandro, Simone Tanelli, and Pavlos Kollias. "Polarization Diversity for Millimeter Spaceborne Doppler Radars: An Answer for Observing Deep Convection?" Journal of Atmospheric and Oceanic Technology 30, no. 12 (December 1, 2013): 2768–87. http://dx.doi.org/10.1175/jtech-d-13-00085.1.
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Abstract Spaceborne Doppler radars have the potential to provide key missing observations of convective vertical air motions especially over the tropical oceans. Such measurements can improve understanding of the role of tropical convection in vertical energy transport and its interaction with the environment. Several millimeter wavelength Doppler radar concepts have been proposed since the 1990s. The Earth Clouds, Aerosols, and Radiation Explorer (EarthCARE) Cloud Profiling Radar (CPR) will be the first Dopplerized atmospheric radar in space but has not been optimized for Doppler measurements in deep convective clouds. The key challenge that constrains the CPR performance in convective clouds is the range–Doppler dilemma. Polarization diversity (PD) offers a solution to this constraint by decoupling the coherency (Doppler) requirement from the unambiguous range requirement. Careful modeling of the radar signal depolarization and its impact on radar receiver channel cross talk is needed to accurately assess the performance of the PD approach. The end-to-end simulator presented in this work allows reproduction of the signal sensed by a Doppler radar equipped with polarization diversity when overpassing realistic three-dimensional convective cells, with all relevant cross-talk sources accounted for. The notional study highlights that multiple scattering is the primary source of cross talk, highly detrimental for millimeter Doppler velocity accuracy. The ambitious scientific requirement of 1 m s−1 accuracy at 500-m integration for reflectivities above −15 dBZ are within reach for a W-band radar with a 2.5-m antenna with optimal values of the pulse-pair interval between 20 and 30 μs but only once multiple scattering and ghost-contaminated regions are screened out. The identification of such areas is key for Doppler accuracies and can be achieved by employing an interlaced pulse-pair mode that measures the cross and the copolar reflectivities. To mitigate the impact of attenuation and multiple scattering, the Ka band has been considered as either alternative or additional to the W band. However, a Ka system produces worse Doppler performances than a W-band system with the same 2.5-m antenna size. Furthermore, in deep convection it results in similar levels of multiple scattering and therefore it does not increase significantly the depth of penetration. In addition, the larger footprint causes stronger nonuniform beam-filling effects. One advantage of the Ka-band option is the larger Nyquist velocity that tends to reduce the Doppler accuracies. More significant benefits are derived from the Ka band when observing precipitation not as intense as the deep convection is considered here. This study demonstrates that polarization diversity indeed represents a very promising methodology capable of significantly reducing aliasing and Doppler moment estimate errors, two main error sources for Doppler velocity estimates in deep convective systems and a key step to achieving typical mission requirements for convection-oriented millimeter radar-based spaceborne missions.
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Bai, Jie, Lianqing Zheng, Sen Li, Bin Tan, Sihan Chen, and Libo Huang. "Radar Transformer: An Object Classification Network Based on 4D MMW Imaging Radar." Sensors 21, no. 11 (June 2, 2021): 3854. http://dx.doi.org/10.3390/s21113854.
Full textAbstract:
Automotive millimeter-wave (MMW) radar is essential in autonomous vehicles due to its robustness in all weather conditions. Traditional commercial automotive radars are limited by their resolution, which makes the object classification task difficult. Thus, the concept of a new generation of four-dimensional (4D) imaging radar was proposed. It has high azimuth and elevation resolution and contains Doppler information to produce a high-quality point cloud. In this paper, we propose an object classification network named Radar Transformer. The algorithm takes the attention mechanism as the core and adopts the combination of vector attention and scalar attention to make full use of the spatial information, Doppler information, and reflection intensity information of the radar point cloud to realize the deep fusion of local attention features and global attention features. We generated an imaging radar classification dataset and completed manual annotation. The experimental results show that our proposed method achieved an overall classification accuracy of 94.9%, which is more suitable for processing radar point clouds than the popular deep learning frameworks and shows promising performance.
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Zrnic, Dusan S., Valery M. Melnikov, and John K. Carter. "Calibrating Differential Reflectivity on the WSR-88D." Journal of Atmospheric and Oceanic Technology 23, no. 7 (July 1, 2006): 944–51. http://dx.doi.org/10.1175/jtech1893.1.
Full textAbstract:
Abstract A calibration procedure of differential reflectivity on the Weather Surveillance Radar-1988 Doppler (WSR-88D) is described. It has been tested on NOAA's modified WSR-88D research and development polarimetric radar and is directly applicable to radars that simultaneously transmit and receive waves having horizontal and vertical polarization.
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Horstmann, Jochen, Jan Bödewadt, Ruben Carrasco, Marius Cysewski, Jörg Seemann, and Michael Streβer. "A Coherent on Receive X-Band Marine Radar for Ocean Observations." Sensors 21, no. 23 (November 25, 2021): 7828. http://dx.doi.org/10.3390/s21237828.
Full textAbstract:
Marine radars are increasingly popular for monitoring meteorological and oceanographic parameters such as ocean surface wind, waves and currents as well as bathymetry and shorelines. Within this paper a coherent on receive marine radar is introduced, which is based on an incoherent off the shelf pulsed X-band radar. The main concept of the coherentization is based on the coherent on receive principle, where the coherence is achieved by measuring the phase of the transmitted pulse from a leak in the radar circulator, which then serves as a reference phase for the transmitted pulse. The Doppler shift frequency can be computed from two consecutive pulse-pairs in the time domain or from the first moment of the Doppler spectrum inferred by means of a short time Fast Fourier Transform. From the Doppler shift frequencies, radial speed maps of the backscatter of the ocean surface are retrieved. The resulting backscatter intensity and Doppler speed maps are presented for horizontal as well as vertical polarization, and discussed with respect to meteorological and oceanographic applications.
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Ilyin, M. Yu, A. A. Kim, I. S. Razuvaeva, and N. V. Sotnikova. "RADIO-PHOTON MULTILOOP DELAY LINE FOR MONITORING AND VERIFICATION OF TECHNICAL PARAMETERS OF DOPPLER RADAR SYSTEM." Issues of radio electronics, no. 7 (July 20, 2018): 44–50. http://dx.doi.org/10.21778/2218-5453-201-7-44-50.
Full textAbstract:
One of them actual problems of development doppler radar is technical parameters quality control. Especially it concerns the development of reference standards for sounding and imitation of Doppler shifts of the carrier frequencies of the radar, which is difficult and economically unprofitable task. The article considers the possibility of measuring and controlling the technical parameters of meteorological Doppler radars using the time delay multi-loop radio-photon system for imitation distance and Doppler shift. A method for controlling the range, spatial resolution, blind zone, sensitivity of the receiver, as well as the accuracy of determining the wind speed along the beam is proposed on the basis of data obtained as a result of the calibration bench for metrological control of laser meteorological locators prototype development. Methods for checking the trace standards and Doppler shifts in a radio-photon imitation multi-loop time delay line are proposed.