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Dissertations / Theses on the topic 'Doppler Weather Radar Data'
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1
Watson, Robert J. "Data comparisons for spatially separated meteorological radars." Thesis, University of Essex, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337180.
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Ernvik, Aron. "3D visualization of weather radar data." Thesis, Linköping University, Department of Electrical Engineering, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-1053.
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There are 12 weather radars operated jointly by smhi and the Swedish Armed Forces in Sweden. Data from them are used for short term forecasting and analysis. The traditional way of viewing data from the radars is in 2D images, even though 3D polar volumes are delivered from the radars. The purpose of this work is to develop an application for 3D viewing of weather radar data.
There are basically three approaches to visualization of volumetric data, such as radar data: slicing with cross-sectional planes, surface extraction, and volume rendering. The application developed during this project supports variations on all three approaches. Different objects, e.g. horizontal and vertical planes, isosurfaces, or volume rendering objects, can be added to a 3D scene and viewed simultaneously from any angle. Parameters of the objects can be set using a graphical user interface and a few different plots can be generated.
Compared to the traditional 2D products used by meteorologists when analyzing radar data, the 3D scenes add information that makes it easier for the users to understand the given weather situations. Demonstrations and discussions with meteorologists have rendered positive reactions. The application will be installed and evaluated at Arlanda airport in Sweden.
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Tilford, Kevin A. "Weather radar data for operational hydrology." Thesis, University of Salford, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315383.
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Wilson, Damian R. "Advanced polarization and Doppler radar techniques to study precipitation microphysics." Thesis, University of Reading, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.284066.
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Aygar, Alper. "Doppler Radar Data Processing And Classification." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609890/index.pdf.
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In this thesis, improving the performance of the automatic recognition of the Doppler radar targets is studied. The radar used in this study is a ground-surveillance doppler radar. Target types are car, truck, bus, tank, helicopter, moving man and running man. The input of this thesis is the output of the real doppler radar signals which are normalized and preprocessed (TRP vectors: Target Recognition Pattern vectors) in the doctorate thesis by Erdogan (2002). TRP vectors are normalized and homogenized doppler radar target signals with respect to target speed, target aspect angle and target range. Some target classes have repetitions in time in their TRPs. By the use of these repetitions, improvement of the target type classification performance is studied. K-Nearest Neighbor (KNN) and Support Vector Machine (SVM) algorithms are used for doppler radar target classification and the results are evaluated. Before classification PCA (Principal Component Analysis), LDA (Linear Discriminant Analysis), NMF (Nonnegative Matrix Factorization) and ICA (Independent Component Analysis) are implemented and applied to normalized doppler radar signals for feature extraction and dimension reduction in an efficient way. These techniques transform the input vectors, which are the normalized doppler radar signals, to another space. The effects of the implementation of these feature extraction algoritms and the use of the repetitions in doppler radar target signals on the doppler radar target classification performance are studied.
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Aulich, Graydon D. "Development of a bistatic Doppler radar system using an incoherent transmitter." Thesis, University of Reading, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.284452.
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Carlsson, Andreas. "A comparison between wind measurements with doppler weather radar and rawinds." Thesis, Uppsala universitet, Meteorologiska institutionen, 1996. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-392766.
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Comparisons between wind measurement with doppler weather radar and wind measurement with rawinds in different weather situations is done. The study is made in a statistical way with some comparable parameters as outcome. The importance of the weather and different weather situation’s effect on the results are discussed, both in form of the winds accuracy and the probability of getting any wind at all as outcome. The study shows that wind measurement with doppler radar at lower elevations not has so good accuracy, but it becomes better the higher up we measure. At the same time will we lose a lot of the measurements at higher levels by the reason that the reflected power is weakened very fast with the distance the transmitted ray travel. The doppler effect is explained and the by SMHI used routine for wind measurement with radar is described. At the end of the work are some problems and disadvantages with the radar measurements and the used method discussed.
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Tomlin, Christopher Michael. "Adaptive flood forecasting using weather radar data." Thesis, Lancaster University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322340.
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Altube, Vázquez Patricia. "Procedures for improved weather radar data quality control." Doctoral thesis, Universitat de Barcelona, 2016. http://hdl.handle.net/10803/400398.
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Weather radar data and its downstream products are essential elements in weather surveillance and key parameters in the initialisation and validation of hydrological and meteorological models, among other downstream applications. Following the quality standards established by the European and global weather radar networking referents, the present thesis aims for the improvement of the base data quality control in the regional weather radar network operated by the Meteorological Service of Catalonia, the XRAD. This objective is accomplished through the analysis, development and implementation of new or existing procedures and algorithms for radar data quality assessment and improvement. Attending to the current radar technology and to the already implemented quality control procedures for the XRAD, the work is focused on the continuous evaluation of the radar system calibration status and on the correction of Doppler velocity data. The quality control algorithms and recommendations presented are easily translatable to any other operative weather radar networking environment.
A Sun-based, fully automatic procedure for online monitoring the antenna alignment and the receiver chain calibration is adapted and operationally implemented for the XRAD. This Sun-monitoring technique was developed at the Royal Netherlands and Finnish Meteorological Institutes and is included in the quality control flow of numerous weather radar networks around the world. The method is modified for a robust detection and characterisation of solar interferences in raw data at all scan elevations, even when only data at relatively short ranges is available. The modified detection algorithm is also suitable for detecting interferences from wireless devices, which are stored for monitoring their incidence in the XRAD. The solar interferences detected, in turn, are input observations for the inversion of a two-dimensional Gaussian model that yields estimates of the calibration parameters of interest. A complete theoretical derivation of the model establishes its validity limits and provides analytical estimates of the effective solar widths directly from radar parameters. Results of application of this Sun-monitoring methodology to XRAD data reveal its ability to determine the accuracy of the antenna pointing and to detect changes in receiver calibration and radar system operation status.
In order to facilitate the usage of the Sun-monitoring technique and the interpretation of its estimates, the methodology is reproduced under controlled conditions based on the distributions of solar observations collected by two of the XRAD radars. The analysis shows that the accuracy of the estimated calibration parameters is conditioned by the precision, number and distribution of the solar observations which constitute key variables that need to be controlled to ensure reliable estimates. In addition, the Sun-monitoring technique is compared under actual operative conditions with two other common techniques for quantifying the antenna azimuth and elevation pointing offsets. Pointing bias estimates gathered in a dedicated short-term campaign are studied in a direct inter- comparison of the methods that reflects the advantages and limitations in each case. The analysis of the bias estimates reported by the methods in the course of a one-year period reveals that the performance of the techniques depends on the antenna position at the time of the measurement. After this study, a reanalysis of the Sun-monitoring method results is proposed, which allows to additionally quantify the antenna pedestal levelling error.
Finally, a post-processing, spatial image filtering algorithm for identification and correction of unfolding errors in dual-PRF Doppler velocity data is proposed. The correction of these errors benefits the usage of radar velocity data in downstream applications such as wind- shear and mesocyclone detection algorithms or assimilation in numerical weather prediction models. The main strengths of the proposed algorithm, in comparison with existing correction techniques, are its robustness to the presence of clustered unfolding errors and that it can be employed independently of post-processing dealiasing algorithms. By means of simulated dual-PRF velocity fields, the correction ability of the algorithm is quantitatively analysed and discussed with particular emphasis on the correction of clustered errors. The quality improvement in real dual-PRF data brought out by the new algorithm is illustrated through application to three selected severe weather events registered by the XRAD.Seguint els estàndards de qualitat establerts per a les xarxes de radars meteorològics de referència a nivell europeu i global, la present tesi té com a objectiu la millora del control de qualitat de les dades de la xarxa regional de radars meteorològics operada pel Servei Meteorològic de Catalunya (la XRAD). Atenent als procediments de control de qualitat ja implementats per a la XRAD, el treball es centra en l'avaluació contínua de l'estat del calibratge del sistema radar i en la correcció de les dades de velocitat Doppler. Es presenta l'adaptació i aplicació d’un procediment totalment automàtic basat en el Sol, que permet la quantificació remota dels errors d'alineació de l'antena i de calibratge en recepció del radar a la XRAD. El mètode ha estat modificat per a la detecció i caracterització robusta d'interferències solars a les dades primàries de radar. Les interferències solars són utilitzades per a la inversió d'un model físic que proporciona estimacions dels paràmetres de calibratge d'interès. L'algoritme de detecció modificat també és adequat per a la identificació d'interferències procedents de dispositius electrònics externs. Aquestes interferències són emmagatzemades per al seguiment de la seva incidència a la XRAD. La metodologia solar esmentada es modelitza en condicions controlades a partir de la distribució de les observacions solars recollides per dos dels radars de la XRAD. L'anàlisi mostra que la precisió, el nombre i la distribució de les observacions solars constitueixen variables clau que necessiten ser controlades per garantir estimacions fiables dels paràmetres de calibrage. A més, la tècnica solar es compara, sota condicions operatives reals, amb altres dues tècniques habitualment emprades per a la quantificació de l'error d'apuntament de l'antena. A partir d'aquest estudi, es proposa un nou mètode d'anàlisi de les interferències solars, el cual permet quantificar l'error d'anivellament del pedestal de l'antena. Finalment, es desenvolupa i valida un algoritme de filtrat d'imatges per a la identificació i correcció dels errors característics que es donen lloc a les dades dual-PRF de velocitat Doppler. Els punts forts de l'algoritme proposat, en comparació amb les tècniques de correcció existents, són la seva robustesa en la correció d'errors agrupats i que pot emprar- se amb independència dels algoritmes de dealiasing. La millora de la qualitat de les dades reals de velocitat s'il·lustra mitjançant l'aplicació de l’algoritme a tres episodis de temps sever enregistrats per la XRAD.
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Shtarkalev, Bogomil Iliev. "Single data set detection for multistatic Doppler radar." Thesis, University of Edinburgh, 2015. http://hdl.handle.net/1842/10556.
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The aim of this thesis is to develop and analyse single data set (SDS) detection algorithms that can utilise the advantages of widely-spaced (statistical) multiple-input multiple-output (MIMO) radar to increase their accuracy and performance. The algorithms make use of the observations obtained from multiple space-time adaptive processing (STAP) receivers and focus on covariance estimation and inversion to perform target detection. One of the main interferers for a Doppler radar has always been the radar’s own signal being reflected off the surroundings. The reflections of the transmitted waveforms from the ground and other stationary or slowly-moving objects in the background generate observations that can potentially raise false alarms. This creates the problem of searching for a target in both additive white Gaussian noise (AWGN) and highly-correlated (coloured) interference. Traditional STAP deals with the problem by using target-free training data to study this environment and build its characteristic covariance matrix. The data usually comes from range gates neighbouring the cell under test (CUT). In non-homogeneous or non-stationary environments, however, this training data may not reflect the statistics of the CUT accurately, which justifies the need to develop SDS methods for radar detection. The maximum likelihood estimation detector (MLED) and the generalised maximum likelihood estimation detector (GMLED) are two reduced-rank STAP algorithms that eliminate the need for training data when mapping the statistics of the background interference. The work in this thesis is largely based on these two algorithms. The first work derives the optimal maximum likelihood (ML) solution to the target detection problem when the MLED and GMLED are used in a multistatic radar scenario. This application assumes that the spatio-temporal Doppler frequencies produces in the individual bistatic STAP pairs of the MIMO system are ideally synchronised. Therefore the focus is on providing the multistatic outcome to the target detection problem. It is shown that the derived MIMO detectors possess the desirable constant false alarm rate (CFAR) property. Gaussian approximations to the statistics of the multistatic MLED and GMLED are derived in order to provide a more in-depth analysis of the algorithms. The viability of the theoretical models and their approximations are tested against a numerical simulation of the systems. The second work focuses on the synchronisation of the spatio-temporal Doppler frequency data from the individual bistatic STAP pairs in the multistatic MLED scenario. It expands the idea to a form that could be implemented in a practical radar scenario. To reduce the information shared between the bistatic STAP channels, a data compression method is proposed that extracts the significant contributions of the MLED likelihood function before transmission. To perform the inter-channel synchronisation, the Doppler frequency data is projected into the space of potential target velocities where the multistatic likelihood is formed. Based on the expected structure of the velocity likelihood in the presence of a target, a modification to the multistatic MLED is proposed. It is demonstrated through numerical simulations that the proposed modified algorithm performs better than the basic multistatic MLED while having the benefit of reducing the data exchange in the MIMO radar system.
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Robinson, Sean D. "Utility of tactical environmental processor (TEP) as a Doppler at-sea weather radar." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2002. http://library.nps.navy.mil/uhtbin/hyperion-image/02Jun%5FRobinson.pdf.
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Michelson, Daniel Brause. "Quality control of weather radar data for quantitative application." Thesis, University of Salford, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.400829.
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Bray, Michaela Therese Julia. "Rainfall analysis based on rain gauge and weather radar data and numerical weather modelling." Thesis, University of Bristol, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.500432.
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Yuan, J. "Hydrological modelling with weather radar data in urban drainage systems." Thesis, University of Salford, 1994. http://usir.salford.ac.uk/2085/.
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The management of large scale strategic urban combined drainage systems is becoming increasingly dependent upon weather radar systems which can provide quantitative precipitation information to improve the overall efficiency of a system's operational performance. Thus, there has been an increasing requirement for a more detailed knowledge of the radar rainfall data accuracy and the development of a mathematical rainfall-runoff model that can be used to analyse and control a system in real-time. Within this context, several important factors including signal attenuation, temporal and spatial data resolutions and rainfall quantisation schemes that determine the accuracy of radar rainfall estimates were examined in this thesis. In order to facilitate real-time flow simulation and forecast, a Conceptually Parametrised Transfer Function (CPTF) model has been developed based on Dynamic Linear Reservoir theory. The model is structurally simple and operationally reliable. It can be easily identified and robustly updated following a pulse response-to-CPTF procedure in which Genetic Algorithms play a key role. Using the model, the accuracy of areal rainfall estimates obtained by the Hameldon Hill radar has been assessed, firstly by comparing the radar rainfall estimates with `ground truth', and then by comparing the simulated hydrographs with the actual flow observations. Finally, a case study was conducted using radar rainfall data to highlight the potential benefit of real-time control for the strategic urban drainage system in the Fylde Coast. The major achievements documented in this thesis are: 1) A rule for determination of an appropriate input data resolution for hydrological models; 2) A general probability density function for describing the sampled radar rainfall intensities; 3) An efficient quantising law (ß-Law) and an associated adaptive rainfall quantisation scheme; 4) Three general conceptual pulse-response functions developed based on Dynamic Linear Reservoir theory; 5) CPTF model; and 6) A case study on the potential benefit of real-time control in the Fylde urban drainage system.
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Mittermaier, Marion Petra. "Investigating synergies between weather radar data and mesoscale model output." Thesis, University of Reading, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.397752.
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Harasti, Paul Robert. "Hurricane properties by principal component analysis of Doppler radar data." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq53836.pdf.
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Boodoo, Sudesh. "Estimation of drop-size distributions from deconvolved doppler radar data." Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=69698.
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A 915 MHz Doppler radar was able under certain conditions to provide Doppler spectra containing separate and distinct modes due to scattering by rain and by the clear air. The rain spectra are broadened and shifted on the velocity axis due to turbulent air motions. Information in the clear air mode is used to correct for these effects, leaving in the rain spectra the reflectivity-weighted distribution of drop fall speed, from which the drop-size distribution can be computed.The fast Fourier transform and two iterative methods of deconvolution were applied to simulated Doppler spectra. We concluded that the iterative methods of deconvolution are more appropriate than the fast Fourier transform. Of the two iterative methods, Jansson's method of deconvolution, including prefiltering of the data, was found to give better results than Van Cittert's method.
Jansson's method was applied to biomodal spectra obtained from the HARP project of 1990 in Hawaii and to spectra obtained from a similar radar operated in Montreal. Evident is the different characteristics of rainfall in both regions and the appropriateness of the same deconvolution method to different classes of spectra.
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Hart, Dennis L., and Marvin A. Smith. "AIM-120A DOPPLER RADAR TELEMETRY DATA REDUCTION AND ANALYSIS SOFTWARE." International Foundation for Telemetering, 1994. http://hdl.handle.net/10150/608575.
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International Telemetering Conference Proceedings / October 17-20, 1994 / Town & Country Hotel and Conference Center, San Diego, CaliforniaThis paper describes the application software used to convert AIM-120A, Advanced Medium Range Air-to-Air Missile (AMRAAM), telemetry data to a series of color images and time-correlated engineering unit results. X Window System-based graphics facilitate visualization of the doppler radar data. These software programs were developed for the VAX/VMS and DEC Alpha environments.
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De, Elía Ramón. "A study of wind field retrieval from single Doppler radar data /." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ37113.pdf.
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Fernandez-Duran, Juan Jose. "Statistical techniques for clutter removal and attentuation detection in weather radar data." Thesis, University of Essex, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243358.
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Gonzalez-Ramirez, Efren. "Weather radar data analysis oriented to improve the quality of rainfall estimation." Thesis, University of Bristol, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.424642.
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Laroche, Stéphane. "Variational analysis methods for retrieval of wind field from single-doppler radar data." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=28818.
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The variational analysis methods are applied to retrieve the steady state wind field from single-Doppler radar data. The wind field is retrieved by fitting, in the least-squares sense, constraining model equations to observations measured during a short assimilation period (2 or 3 time sequences). The weak and strong constraint formalisms are reviewed and examined using the one-dimensional linear advection equation as a constraint. It is shown that the retrieval is not unique, but the problem can be controlled by a smoothness constraint. Variational two-dimensional and three-dimensional wind retrieval algorithms are developed and tested using actual dual-Doppler radar data. The conservation of reflectivity and the radial momentum equation are used as weak constraints in both algorithms. The anelastic form of the continuity equation is also included as a strong constraint in the three-dimensional algorithm. The two-dimensional algorithm is tested and compared to echo tracking methods using Doppler radar observations in the clear-air planetary boundary layer. The resolution at which the methods can effectively retrieve the horizontal wind field is examined in detail. The variational algorithm can properly retrieve wind structures greater than 10 km wavelength. The three-dimensional algorithm is tested using observations of a precipitating microburst. It is demonstrated that the three-dimensional wind field can be retrieved, but the method fails near the ground level. In addition, the retrieval is sensitive to the radar position relative to the observational domain due to systematic model errors. The computational efficiency of the three-dimensional wind retrieval algorithm allows its semi-operational implementation at the J. S. Marshall Radar Observatory of McGill University.
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Da, Silveira Reinaldo Bomfim. "Recognition of clutter in weather radars using polarization diversity information and artificial neural networks." Thesis, University of Essex, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.265022.
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Hajjam, Sohrab. "Real-time flood forecasting model intercomparison and parameter updating rain gauge and weather radar data." Thesis, University of Salford, 1997. http://usir.salford.ac.uk/43019/.
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This thesis describes the development of real-time flood forecasting models at selected catchments in the three countries, using rain gauge and radar derived rainfall estimates and time-series analysis. An extended inter-comparison of real-time flood forecasting models has been carried out and an attempt has been made to rank the flood forecasting models. It was found that an increase in model complexity does not necessarily lead to an increase in forecast accuracy. An extensive analysis of group calibrated transfer function (TF) models on the basis of antecedent conditions of the catchment and storm characteristics has revealed that the use of group model resulted in a significant improvement in the quality of the forecast. A simple model to calculate the average pulse response has also been developed. The development of a hybrid genetic algorithm (HGA), applied to a physically realisable transfer function model is described. The techniques of interview selection and fitness scaling as well as random bit mutation and multiple crossover have been included, and both binary and real number encoding technique have been assessed. The HGA has been successfully applied for the identification and simulation of the dynamic TF model. Four software packages have been developed and extensive development and testing has proved the viability of the approach. Extensive research has been conducted to find the most important adjustment factor of the dynamic TF model. The impact of volume, shape and time adjustment factors on forecast quality has been evaluated. It has been concluded that the volume adjustment factor is the most important factor of the three. Furthermore, several attempts have been made to relate the adjustment factors to different elements. The interaction of adjustment factors has also been investigated. An autoregressive model has been used to develop a new updating technique for the dynamic TF model by the updating of the B parameters through the prediction of future volume adjustment factors over the forecast lead-time. An autoregressive error prediction model has also been combined with a static TF model. Testing has shown that the performance of both new TF models is superior to conventional procedures.
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Dai, Chengyu. "Exploration of Weather Impacts on Freeway Traffic Operations and Safety Using High-Resolution Weather Data." PDXScholar, 2011. https://pdxscholar.library.pdx.edu/open_access_etds/255.
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Adverse weather is considered as one of the important factors contributing to injuries and severe crashes. During rainy conditions, it can reduce travel visibility, increase stopping distance, and create the opportunity hydroplaning. This study quantified the relative crash risk on Oregon 217 southbound direction under rainy conditions by using a match-paired approach, applied one-year traffic data, crash data and NEXRAD Level II radar weather data. There are 26 crashes occurred in match-paired weather conditions for Oregon 217 in year 2007. The results of this study indicate that a higher crash risk and a higher property-damage-only crash risk occurred during rainy days. The crash risk level varies by the location of the highway, at milepost 2.55 station SW Allen Blvd has the highest driving risks under rainy conditions.
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Pfaff, Thomas [Verfasser], and András [Akademischer Betreuer] Bárdossy. "Processing and analysis of weather radar data for use in hydrology / Thomas Pfaff. Betreuer: András Bárdossy." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2013. http://d-nb.info/1033714135/34.
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Kreklow, Jennifer [Verfasser]. "Improving usability of weather radar data in environmental sciences : potentials, challenges, uncertainties and applications / Jennifer Kreklow." Hannover : Gottfried Wilhelm Leibniz Universität Hannover, 2020. http://d-nb.info/1220422231/34.
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Kahyaoglu, Nazli Deniz. "Spectral And Statistical Analyses Of Experimental Radar Clutter Data." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612799/index.pdf.
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The performance of radar detection and imaging systems strongly depends on the characteristics of radar clutter. In order to improve the radar signal processing algorithms, successful analysis and modeling of radar clutter are required. For a successful model of radar clutter, both the spectral and statistical characteristics of the clutter should be revealed. Within the scope of this study, an experimental radar data acquisition system is established to analyze radar clutter. The hardware and the data processing system are first verified using generic signals and then a set of measurements is taken in the open terrain. In this thesis, the limitations and problems encountered during the establishment of the system are explained in detail. The spectral and statistical analyses performed on the recorded data are examined. The temporal
and spatial behavior of the measured clutter data are explored. The hypothetical models proposed so far in the literature are tested on the experimental data and the fitting of models to the experimental data is confirmed using various goodness-of-fit tests. Finally, the results of the analyses are interpreted in the light of the radar system parameters and the characteristics of the illuminated terrain.
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Christiansen, Jonas Myhre. "DVB-T based Passive Bistatic Radar : Simulated and experimental data analysis of range and Doppler walk." Thesis, Norwegian University of Science and Technology, Department of Engineering Cybernetics, 2009. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-9849.
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Chung, Kao-Shen. "Use of single Doppler radar observations in data assimilation at convective scale with model as a weak constraint." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:8881/R/?func=dbin-jump-full&object_id=92252.
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Aiazzi, Lorenzo. "Combined analysis of C-band polarimetric radar and disdrometer data of convective and stratiform precipitation." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/22121/.
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The aim of the present Thesis is to observe the characteristics of the precipitation and to check the quality of the radar data under different meteorological conditions. This aim is achieved through a combined analysis of the data collected by two instruments that have different operating principles: a C-band polarimetric radar and a PARSIVEL2 disdrometer. Radar variables are compared with the characteristics and the microphysics evolution of the precipitation retrieved by the disdrometer. The disdrometer is located in the city center of Bologna, at about 28 km far from the radar site. The combined analysis of the two instruments is done for a dataset that includes 11 months of the years 2019 and 2020. The dataset contains convective and stratiform precipitation events. The lower radar elevations are affected by anthropogenic interferences that slightly reduce the dataset extension. The analyses show a good correlation between the reflectivity factors retrieved by the radar and by the disdrometer through the Drop Size Distribution (DSD). The correlation coefficient between the two estimations is 0.84. A verification of the operational algorithm of the hydrometeor classification is obtained through the radar data. Moreover, the convective and stratiform discrimination developed through the disdrometer data is consistent with the polarimetric variables of the radar. For example, the distribution of the differential reflectivity peaks for higher values in a regime of convective precipitation in comparison to the stratiform regime. The convective distribution of the differential reflectivity has a median of 1.5 dB, while the stratiform one has a median of 0.9 dB. Lastly, the case study of a thunderstorm occurred in Bologna on May 28th 2019 is described. This case study shows precipitation structures of different intensities and different types of hydrometeors, allowing a verification of the previous results and a more-detailed analysis of the DSD characteristics.
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Bachmann, Kevin [Verfasser], and George C. [Akademischer Betreuer] Craig. "Sources of predictability for deep convection : radar data assimilation, orography and weather regime / Kevin Bachmann ; Betreuer: George C. Craig." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2019. http://d-nb.info/1188200380/34.
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Gordon, Ronald Walter. "Impact of Assimilating Airborne Doppler Radar Winds on the Inner-Core Structure and Intensity of Hurricane Ike (2008)." Scholarly Repository, 2011. http://scholarlyrepository.miami.edu/oa_theses/276.
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Accurate prediction of Tropical Cyclones (TC) is vital for the protection of life and property in areas that are prone to their destructive forces. While significant improvements have been made in forecasting TC track, intensity remains a challenge. It is hypothesized that accurate TC intensity forecast requires, among other things, an adequate initial description of their inner-core region. Therefore, there must be reliable observations of the inner-core area of the TC and effective data assimilation (DA) methods to ingest these data into the Numerical Weather Prediction (NWP) models. However, these requirements are seldom met at the relatively low resolution of operational global prediction models and the lack of routine observations assimilated in the TC inner-core. This study tests the impacts of assimilating inner-core Airborne Doppler Radar (ADR) winds on the initial structure and subsequent intensity forecast of Hurricane Ike (2008). The 4-dimensional variational (4DVar) and the 3-dimensional variational (3DVar) methods are used to perform DA while the Weather Research and Forecasting (WRF) model is used to perform forecasts. It is found that assimilating data helps to initialize a more realistic inner-core structure using both DA methods. Additionally, the resulting short-term and long-term intensity forecasts are more accurate when data is assimilated versus cases when there is no DA. Additionally, it is found that in some cases the impact of DA lasts up to 12 hours longer with 4DVar versus 3DVar. It is shown that this is because the flow-dependent 4DVar method produces more dynamically and balanced analysis increments compared to the static and isotropic increments of 3DVar. However, the impact of using both methods is minimal in the long-range. The analyses show that at longer forecast range the dynamics of hurricane Ike was influenced more by outer environment features than the inner-core winds.
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Boon, Dirk Francois. "The link between daily rainfall and satellite radar backscatter data from the ERS-2 scatterometer in the Free State Province, South Africa." Diss., Pretoria : [s.n.], 2007. http://upetd.up.ac.za/thesis/available/etd-10272008-132211.
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Kazemisaber, Mohammadreza. "Clutter Removal in Single Radar Sensor Reflection Data via Digital Signal Processing." Thesis, Linnéuniversitetet, Institutionen för fysik och elektroteknik (IFE), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-99874.
Full textAbstract:
Due to recent improvements, robots are more applicable in factories and various production lines where smoke, fog, dust, and steam are inevitable. Despite their advantages, robots introduce new safety requirements when combined with humans. Radars can play a crucial role in this context by providing safe zones where robots are operating in the absence of humans. The goal of this Master’s thesis is to investigate different clutter suppression methods for single radar sensor reflection data via digital signal processing. This was done in collaboration with ABB Jokab AB, Sweden. The calculations and implementation of the digital signal processing algorithms are made with Octave. A critical problem is false detection that could possibly cause irreparable damage. Therefore, a safety system with an extremely low false alarm rate is desired to reduce costs and damages. In this project, we have studied four different digital low pass filters: moving average, multiple-pass moving average, Butterworth, and window-based filters. The results are compared, and it is ascertained that all the results are logically compatible, broadly comparable, and usable in this context.
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Lange, Heiner [Verfasser], and George C. [Akademischer Betreuer] Craig. "On the use of radar and aircraft data in Ensemble Data Assimilation of convection for non-hydrostatic numerical weather prediction / Heiner Lange ; Betreuer: George C. Craig." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2016. http://d-nb.info/1122435789/34.
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Chae, Chun Sik. "Studies of the Interferometric Phase and Doppler Spectra of Sea Surface Backscattering Using Numerically Simulated Low Grazing Angle Backscatter Data." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1331074430.
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Orellana, Alvear Johanna Marlene [Verfasser], and Jörg [Akademischer Betreuer] Bendix. "Exploitation of X-band weather radar data in the Andes high mountains and its application in hydrology: a machine learning approach / Johanna Marlene Orellana Alvear ; Betreuer: Jörg Bendix." Marburg : Philipps-Universität Marburg, 2021. http://d-nb.info/1227580185/34.
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Jomaa, Diala. "The Optimal trigger speed of vehicle activated signs." Licentiate thesis, Högskolan Dalarna, Mikrodataanalys, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:du-17538.
Full textAbstract:
The thesis aims to elaborate on the optimum trigger speed for Vehicle Activated Signs (VAS) and to study the effectiveness of VAS trigger speed on drivers’ behaviour. Vehicle activated signs (VAS) are speed warning signs that are activated by individual vehicle when the driver exceeds a speed threshold. The threshold, which triggers the VAS, is commonly based on a driver speed, and accordingly, is called a trigger speed. At present, the trigger speed activating the VAS is usually set to a constant value and does not consider the fact that an optimal trigger speed might exist. The optimal trigger speed significantly impacts driver behaviour. In order to be able to fulfil the aims of this thesis, systematic vehicle speed data were collected from field experiments that utilized Doppler radar. Further calibration methods for the radar used in the experiment have been developed and evaluated to provide accurate data for the experiment. The calibration method was bidirectional; consisting of data cleaning and data reconstruction. The data cleaning calibration had a superior performance than the calibration based on the reconstructed data. To study the effectiveness of trigger speed on driver behaviour, the collected data were analysed by both descriptive and inferential statistics. Both descriptive and inferential statistics showed that the change in trigger speed had an effect on vehicle mean speed and on vehicle standard deviation of the mean speed. When the trigger speed was set near the speed limit, the standard deviation was high. Therefore, the choice of trigger speed cannot be based solely on the speed limit at the proposed VAS location. The optimal trigger speeds for VAS were not considered in previous studies. As well, the relationship between the trigger value and its consequences under different conditions were not clearly stated. The finding from this thesis is that the optimal trigger speed should be primarily based on lowering the standard deviation rather than lowering the mean speed of vehicles. Furthermore, the optimal trigger speed should be set near the 85th percentile speed, with the goal of lowering the standard deviation.
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Phruksahiran, Narathep. "Polarimetrische Streuungseigenschaften und Fokussierungsmethoden zur quantitativen Auswertung der polarimetrischen SAR-Daten." Doctoral thesis, Universitätsbibliothek Chemnitz, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-107764.
Full textAbstract:
Das Radar mit synthetischer Apertur (Synthetic Aperture Radar - SAR) liefert eine quasi-fotographische Abbildung der beleuchteten Bodenoberfläche mit zusätzlichen Informationen, die von der gesendeten und empfangenen Polarisation der Wellen abhängig sind. Eine nützliche Anwendung der polarimetrischen SAR-Daten liegt bei der Klassifizierung der Bodenstruktur anhand der polarimetrischen Streuungseigenschaften.
In diesem Zusammenhang beschäftigt sich die vorliegende Arbeit mit der Entwicklung und Untersuchung neuer polarimetrischen Fokussierungsfunktion für die SAR-Datenverarbeitung mit Hilfe der polarimetrischen Rückstreuungseigenschaft, die zu einer alternativen quantitativen Auswertung der polarimerischen SAR-Daten führen kann.
Die physikalische Optik Approximation wird für die numerische Berechnung der rückgestreuten elektrischen Felder der kanonischen Ziele unter SAR-Geometrie unter Berücksichtigung der Polarisationslage verwendet. Aus den rückgestreuten elektrischen Felder werden die polarimetrischen Radarrückstreuquerschnitte berechnet.
Ein SAR-Simulator wird zur Datenverarbeitung der E-SAR des DLR entwickelt. Der Ansatz des polarimetrischen Radarrückstreuquerschnittes ermöglicht die approximierte numerische Berechnung der Rückstreuungseigenschaften der kanonischen Ziele sowohl im kopolaren als auch im kreuzpolaren Polarisationsbetrieb.
Bei der SAR-Datenverarbeitung werden die Rohdatensätze durch die Referenzfunktion eines Punktzieles in der Entfernungsrichtung verarbeitet. Bei der Azimutkompression werden die vier Referenzfunktionen, das heißt die Referenzfunktion eines Punktzieles, die polarimetrische Fokussierungsfunktion einer flachen Platte, die polarimetrische Fokussierungsfunktion eines Zweifach-Reflektors und die polarimetrische Fokussierungsfunktion eines Dreifach-Reflektors, eingesetzt.
Die qunatitativen Auswertung der SAR-Daten werden anhand des Pauli-Zerlegungstheorems, der differentiellen Reflektivität und des linearen Depolarisationsverhältnises durchgeführt.
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Andrew, Lucia. "Investigating the Effects of Rainfall on Traffic Operations on Florida Freeways." UNF Digital Commons, 2019. https://digitalcommons.unf.edu/etd/904.
Full textAbstract:
Rainfall affects the performance of traffic operations and endangers safety. A common and conventional method (rain gauges) for rainfall measurements mostly provide precipitation records in hourly and 15-minute intervals. However, reliability, continuity, and wide area coverage pose challenges with this data collection method. There is also a greater likelihood for data misrepresentation in areas where short duration rainfall is predominant, i.e., reported values may not reflect the actual equivalent rainfall intensity during subintervals over the entire reporting period. With recent weather and climate patterns increasing in severity, there is a need for a more effective and reliable way of measuring rainfall data used for traffic analyses. This study deployed the use of precipitation radar data to investigate the spatiotemporal effect of rainfall on freeways in Jacksonville, Florida. The linear regression analysis suggests a speed reduction of 0.75%, 1.54%, and 2.25% for light, moderate, and heavy rainfall, respectively. Additionally, headways were observed to increase by 0.26%, 0.54%, and 0.79% for light, moderate, and heavy rainfall, respectively. Measuring precipitation from radar data in lieu of using rain gauges has potential for improving the quality of weather data used for transportation engineering purposes. This approach addresses limitations experienced with conventional rain data, especially since conventional collection methods generally do not reflect the spatiotemporal distribution of rainfall.
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Bhattacharya, Anwesa. "Cloud Properties Over SHAR Region Derived From Weather RADAR Data." Thesis, 2009. https://etd.iisc.ac.in/handle/2005/1009.
Full textAbstract:
Weather radars are increasingly used for the study of clouds, understanding the precipitation systems and also for forecasting very short range weather (one hour to a few hours). Now, Doppler Weather Radar (DWR) data are available in India and it is possible to study cloud properties at fine temporal and spatial scales. Radar is a complex system and calibration of a radar is not an easy job. But derived cloud properties strongly depend on the absolute magnitude of the reflectivity. Therefore, there is a need to check how data from two or more radars compare if they measure a common volume. Chennai and SHAR radars are within 66 km from each other, and the data collected during their calibration and intercomparison experiment in 2006 enables the comparison of their reflectivity(Z) values. Individual reflectivity are compared after plotting SHAR versus Chennai in a scatter plot. Fitting a least square linear best fit line shows that the intercept has a value around 6 dBZ and the slope of the line is 1.06. Thus, there is a trend as well, and the difference between the two radars increase with Z, and for Z around 40 dBZ (for SHAR DWR), the difference between the two is around 8.5 dBZ. Visual intercomparison also validated the results. Data from the two radars are compared with Precipitation Radar (PR) data on board TRMM satellite. TRMM radar slightly overestimates compared to Chennai radar above the range of 30 dBZ. After standardized, SHAR data is used for understanding the evolution and propagation of cloud systems. The diurnal variation in convection is strong in the study region, with increase around local evening and morning and weakening around midnight except in December. Average liquid water content in the clouds is about 0.5 gm/m3. There is some seasonal dependence but no clear dependence on cloud size. Smaller systems of May have more liquid water content compared to larger ones. For nowcasting vertically projected maximum reflectivity is taken. A threshold of 30 dBZ is set to identify the cloud systems. Both center of gravity tracking (CG) and cross-correlation (CC) methods are used to track them. Frequent merging and splitting is common in the clouds which makes storm tracking difficult. Tracking by CC is giving better result than that by the CG method in the case of large systems (i.e., clusters). For smaller systems (individual cloud systems), CC method gives better result than CG method but not as good as cluster.
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Bhattacharya, Anwesa. "Cloud Properties Over SHAR Region Derived From Weather RADAR Data." Thesis, 2009. http://hdl.handle.net/2005/1009.
Full textAbstract:
Weather radars are increasingly used for the study of clouds, understanding the precipitation systems and also for forecasting very short range weather (one hour to a few hours). Now, Doppler Weather Radar (DWR) data are available in India and it is possible to study cloud properties at fine temporal and spatial scales. Radar is a complex system and calibration of a radar is not an easy job. But derived cloud properties strongly depend on the absolute magnitude of the reflectivity. Therefore, there is a need to check how data from two or more radars compare if they measure a common volume. Chennai and SHAR radars are within 66 km from each other, and the data collected during their calibration and intercomparison experiment in 2006 enables the comparison of their reflectivity(Z) values. Individual reflectivity are compared after plotting SHAR versus Chennai in a scatter plot. Fitting a least square linear best fit line shows that the intercept has a value around 6 dBZ and the slope of the line is 1.06. Thus, there is a trend as well, and the difference between the two radars increase with Z, and for Z around 40 dBZ (for SHAR DWR), the difference between the two is around 8.5 dBZ. Visual intercomparison also validated the results. Data from the two radars are compared with Precipitation Radar (PR) data on board TRMM satellite. TRMM radar slightly overestimates compared to Chennai radar above the range of 30 dBZ. After standardized, SHAR data is used for understanding the evolution and propagation of cloud systems. The diurnal variation in convection is strong in the study region, with increase around local evening and morning and weakening around midnight except in December. Average liquid water content in the clouds is about 0.5 gm/m3. There is some seasonal dependence but no clear dependence on cloud size. Smaller systems of May have more liquid water content compared to larger ones. For nowcasting vertically projected maximum reflectivity is taken. A threshold of 30 dBZ is set to identify the cloud systems. Both center of gravity tracking (CG) and cross-correlation (CC) methods are used to track them. Frequent merging and splitting is common in the clouds which makes storm tracking difficult. Tracking by CC is giving better result than that by the CG method in the case of large systems (i.e., clusters). For smaller systems (individual cloud systems), CC method gives better result than CG method but not as good as cluster.
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Wang, Sheng-Chuan, and 王聖川. "Visualization System for Weather Radar Data." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/37300250668824828825.
Full textAbstract:
碩士國立臺灣海洋大學
資訊工程學系
93
Abstract Doppler radars are useful facilities for sampling meteorological data. By analyzing radar data, meteorologists can get real-time information for weather forecasting, for example, the precipitation density, the formation of hurricane, the wind velocity magnitude, etc. However, in appearance, the raw data do not supply the information directly. Therefore, a visualization system which explores the internal features of radar data is extremely important. In this thesis, a visualization system for analyzing and displaying radar data based on volume rendering techniques is presented. The system uses splatting volume rendering methods for post-processing radar data to generate images with high accuracy and high quality. The gradient and diffusion effects are taken into account in the volume rendering to enhance image quality. A view-dependent LoD visualization technique is also utilized in the splatting algorithm to increase the rendering performance. Furthermore, a three dimensional texture mapping method assisted by graphics hardware is employed in the system to achieve real-time rendering.
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Makkapati, Vishnu Vardhan. "Ultra High Compression For Weather Radar Reflectivity Data." Thesis, 2006. http://etd.iisc.ac.in/handle/2005/389.
Full textAbstract:
Weather is a major contributing factor in aviation accidents, incidents and delays.
Doppler weather radar has emerged as a potent tool to observe weather. Aircraft carry an onboard radar but its range and angular resolution are limited. Networks of ground-based weather radars provide extensive coverage of weather over large geographic regions. It would be helpful if these data can be transmitted to the pilot. However, these data are highly voluminous and the bandwidth of the ground-air communication links is limited and expensive. Hence, these data have to be compressed to an extent where they are
suitable for transmission over low-bandwidth links. Several methods have been developed to compress pictorial data. General-purpose schemes do not take into account the
nature of data and hence do not yield high compression ratios. A scheme for extreme
compression of weather radar data is developed in this thesis that does not significantly degrade the meteorological information contained in these data.
The method is based on contour encoding. It approximates a contour by a set of
systematically chosen ‘control’ points that preserve its fine structure upto a certain level. The contours may be obtained using a thresholding process based on NWS or custom
reflectivity levels. This process may result in region and hole contours, enclosing ‘high’ or ‘low’ areas, which may be nested. A tag bit is used to label region and hole contours. The control point extraction method first obtains a smoothed reference contour by averaging the original contour. Then the points on the original contour with maximum deviation from the smoothed contour between the crossings of these contours are identified and are designated as control points. Additional control points are added midway between
the control point and the crossing points on either side of it, if the length of the segment between the crossing points exceeds a certain length. The control points, referenced with respect to the top-left corner of each contour for compact quantification, are transmitted to the receiving end.
The contour is retrieved from the control points at the receiving end using spline
interpolation. The region and hole contours are identified using the tag bit. The pixels
between the region and hole contours at a given threshold level are filled using the color corresponding to it. This method is repeated till all the contours for a given threshold level are exhausted, and the process is carried out for all other thresholds, thereby resulting in a composite picture of the reconstructed field.
Extensive studies have been conducted by using metrics such as compression ratio,
fidelity of reconstruction and visual perception. In particular the effect of the smoothing factor, the choice of the degree of spline interpolation and the choice of thresholds are studied. It has been shown that a smoothing percentage of about 10% is optimal for most data. A degree 2 of spline interpolation is found to be best suited for smooth contour reconstruction. Augmenting NWS thresholds has resulted in improved visual perception, but at the expense of a decrease in the compression ratio.
Two enhancements to the basic method that include adjustments to the control points to achieve better reconstruction and bit manipulations on the control points to
obtain higher compression are proposed. The spline interpolation inherently tends to
move the reconstructed contour away from the control points. This has been somewhat
compensated by stretching the control points away from the smoothed reference contour.
The amount and direction of stretch are optimized with respect to actual data fields to yield better reconstruction. In the bit manipulation study, the effects of discarding
the least significant bits of the control point addresses are analyzed in detail. Simple bit truncation introduces a bias in the contour description and reconstruction, which is removed to a great extent by employing a bias compensation mechanism. The results obtained are compared with other methods devised for encoding weather radar contours.
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Makkapati, Vishnu Vardhan. "Ultra High Compression For Weather Radar Reflectivity Data." Thesis, 2006. http://hdl.handle.net/2005/311.
Full textAbstract:
Honeywell Technology Solutions Lab, IndiaWeather is a major contributing factor in aviation accidents, incidents and delays. Doppler weather radar has emerged as a potent tool to observe weather. Aircraft carry onboard radars but their range and angular resolution are limited. Networks of ground-based weather radars provide extensive coverage of weather over large geographic regions. It would be helpful if these data can be transmitted to the pilot. However, these data are highly voluminous and the bandwidth of the ground-air communication links is limited and expensive. Hence, these data have to be compressed to an extent where they are suitable for transmission over low-bandwidth links. Several methods have been developed to compress pictorial data. General-purpose schemes do not take into account the nature of data and hence do not yield high compression ratios. A scheme for extreme compression of weather radar data is developed in this thesis that does not significantly degrade the meteorological information contained in these data. The method is based on contour encoding. It approximates a contour by a set of systematically chosen ‘control points’ that preserve its fine structure up to a certain level. The contours may be obtained using a thresholding process based on NWS or custom reflectivity levels. This process may result in region and hole contours, enclosing `high' or `low' areas, which may be nested. A tag bit is used to label region and hole contours. The control point extraction method first obtains a smoothed reference contour by averaging the original contour. Then the points on the original contour with maximum deviation from the smoothed contour between the crossings of these contours are identified and are designated as control points. Additional control points are added midway between the control point and the crossing points on either side of it, if the length of the segment between the crossing points exceeds a certain length. The control points, referenced with respect to the top-left corner of each contour for compact quantification, are transmitted to the receiving end. The contour is retrieved from the control points at the receiving end using spline interpolation. The region and hole contours are identified using the tag bit. The pixels between the region and hole contours at a given threshold level are filled using the color corresponding to it. This method is repeated till all the contours for a given threshold level are exhausted, and the process is carried out for all other thresholds, thereby resulting in a composite picture of the reconstructed field. Extensive studies have been conducted by using metrics such as compression ratio, fidelity of reconstruction and visual perception. In particular the effect of the smoothing factor, the choice of the degree of spline interpolation and the choice of thresholds are studied. It has been shown that a smoothing percentage of about 10% is optimal for most data. A degree 2 of spline interpolation is found to be best suited for smooth contour reconstruction. Augmenting NWS thresholds has resulted in improved visual perception, but at the expense of a decrease in the compression ratio. Two enhancements to the basic method that include adjustments to the control points to achieve better reconstruction and bit manipulations on the control points to obtain higher compression are proposed. The spline interpolation inherently tends to move the reconstructed contour away from the control points. This has been somewhat compensated by stretching the control points away from the smoothed reference contour. The amount and direction of stretch are optimized with respect to actual data fields to yield better reconstruction. In the bit manipulation study, the effects of discarding the least significant bits of the control point addresses are analyzed in detail. Simple bit truncation introduces a bias in the contour description and reconstruction, which is removed to a great extent by employing a bias compensation mechanism. The results obtained are compared with other methods devised for encoding weather radar contours.
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Makkapati, Vishnu Vardhan. "Ultra High Compression For Weather Radar Reflectivity Data." Thesis, 2006. https://etd.iisc.ac.in/handle/2005/311.
Full textAbstract:
Weather is a major contributing factor in aviation accidents, incidents and delays. Doppler weather radar has emerged as a potent tool to observe weather. Aircraft carry onboard radars but their range and angular resolution are limited. Networks of ground-based weather radars provide extensive coverage of weather over large geographic regions. It would be helpful if these data can be transmitted to the pilot. However, these data are highly voluminous and the bandwidth of the ground-air communication links is limited and expensive. Hence, these data have to be compressed to an extent where they are suitable for transmission over low-bandwidth links. Several methods have been developed to compress pictorial data. General-purpose schemes do not take into account the nature of data and hence do not yield high compression ratios. A scheme for extreme compression of weather radar data is developed in this thesis that does not significantly degrade the meteorological information contained in these data.
The method is based on contour encoding. It approximates a contour by a set of systematically chosen ‘control points’ that preserve its fine structure up to a certain level. The contours may be obtained using a thresholding process based on NWS or custom reflectivity levels. This process may result in region and hole contours, enclosing `high' or `low' areas, which may be nested. A tag bit is used to label region and hole contours. The control point extraction method first obtains a smoothed reference contour by averaging the original contour. Then the points on the original contour with maximum deviation from the smoothed contour between the crossings of these contours are identified and are designated as control points. Additional control points are added midway between the control point and the crossing points on either side of it, if the length of the segment between the crossing points exceeds a certain length. The control points, referenced with respect to the top-left corner of each contour for compact quantification, are transmitted to the receiving end.
The contour is retrieved from the control points at the receiving end using spline interpolation. The region and hole contours are identified using the tag bit. The pixels between the region and hole contours at a given threshold level are filled using the color corresponding to it. This method is repeated till all the contours for a given threshold level are exhausted, and the process is carried out for all other thresholds, thereby resulting in a composite picture of the reconstructed field.
Extensive studies have been conducted by using metrics such as compression ratio, fidelity of reconstruction and visual perception. In particular the effect of the smoothing factor, the choice of the degree of spline interpolation and the choice of thresholds are studied. It has been shown that a smoothing percentage of about 10% is optimal for most data. A degree 2 of spline interpolation is found to be best suited for smooth contour reconstruction. Augmenting NWS thresholds has resulted in improved visual perception, but at the expense of a decrease in the compression ratio.
Two enhancements to the basic method that include adjustments to the control points to achieve better reconstruction and bit manipulations on the control points to obtain higher compression are proposed. The spline interpolation inherently tends to move the reconstructed contour away from the control points. This has been somewhat compensated by stretching the control points away from the smoothed reference contour. The amount and direction of stretch are optimized with respect to actual data fields to yield better reconstruction. In the bit manipulation study, the effects of discarding the least significant bits of the control point addresses are analyzed in detail. Simple bit truncation introduces a bias in the contour description and reconstruction, which is removed to a great extent by employing a bias compensation mechanism. The results obtained are compared with other methods devised for encoding weather radar contours.Honeywell Technology Solutions Lab, India
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Huang, Guo-Jhen, and 黃國禎. "Doppler Radar Data Assimilation Using Ensemble Kalman Filter." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/46839192020532932272.
Full textAbstract:
碩士國立中央大學
大氣物理研究所
95
Ensemble Kalman filter (EnKF) is a method for data assimilation. In this study, we apply the Observation System Simulation Experiments (OSSE) type of experimental designs to explore the performance of assimilating Doppler radar data using EnKF. A general purpose non-hydrostatic compressible model, the ARPS (Advanced Regional Prediction System), with complex multi-class microphysics, is employed for conducting all the experiments. Artificial data sets are from a simulated classic storm case that occurred on 20 May 1977 in Del City, Oklahoma. With and without terrain, we investigate the impact of several factors on the model forecasts, with the emphasis on the issue of quantitative precipitation forecast (QPF). These factors consider the number of ensembles, the time interval and frequency of data injection, the area of data availability, and so on. The major results show that using 40 members, and assimilating the radar data once every 5 minutes, can effectively produce the forecasts with sufficient accuracy. Assimilating as many data sets as possible can help to reduce the errors, and prevent the errors from growing to an uncontrollable scale. When the terrain is present and becomes a potential blockage to the radar beams, and if one can assimilate into the model the information of the initial storm development before the storm reaches the lee side of the mountain, then it is still possible to catch the location and pattern of the storm. Such a measure makes the following model forecast maintain its accuracy, even after the storm passes the mountain, and arrives at a region where the radar beams are completely blocked. Finally, to obtain an accurate one-hour QPF also requires an one-hour of radar data assimilation. Overall speaking, the assimilation of Doppler radar data does reveal significant improvements on reducing the forecast errors.
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Wang, Yujen, and 王佑仁. "Using Doppler Weather Radar to Recognizing Raptor Signal during Migration Seasons in Taiwan." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/34938289259972296701.
Full textAbstract:
碩士長榮大學
資訊管理學系碩士班
100
Spring and autumn monsoon affect Taiwan so much that they create many special ecological landscapes. In these landscapes, the migration of Chinese Goshawk and Grey-faced Buzzard is a very exceptional spectacle, and this also enables Taiwan to become a rare stage to study the ecology of migratory raptors in this world. The main object of this study is developing the application technique of Doppler weather radar to detect the signals of migratory raptors. We will analyze immediately the radar echoes signals which output from the weather radar and determine whether these signals in the radar diagram are the signals which are left in the migration of the birds or not. The identification method, Raptor Identification System, developed in this study is using the signal removing method to identify the migratory raptors. This system will remove the cloud and water vapor signals in the radar diagram, and it will distinguish signals of migrating raptors from the remaining signals after removing all traditional water vapor signal and noise. In order to tie in with the flight characteristics (200m ~ 1200m) of migratory raptors, this identification system uses the weather radar to scan in the elevation angle of 0.5 degree and 1.4 degree to detect the signals of migratory raptors. This “Raptor Identification System” has identified a total number of 994,674 weather radar diagram from April 2009 to November 2011. The few cases from the large number raptor migration signals have been identified from nine hundred thousand radar diagrams. These successful identification cases have showed that it’s feasible to apply Doppler weather radar to detect raptor migration signal during the migration season. The automatic “Raptor Identification System” is first development of all recorded time. Successful identification rate is 86.88% in a season statistics for three years. There are four cases that it’s the large number migration signals identified from radar diagrams and calculate raptors fly speed and fly way. The “Raptor Identification System” will help to understand the mystery of fly way for Chinese Goshawk and Gray-Faced Buzzard, and it also can help for the enforcement of conservation to achieve the purpose of conservation during the migratory sessions.
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Reynolds, Amber Elizabeth. "Analysis of 11 june 2003 mesoscale convective vortex genesis using weather surveillance radar ??88 doppler (wsr-88d)." Thesis, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-2423.
Full textAbstract:
Mesoscale convective vortices (MCVs), which typically form within the stratiform rain of some mesoscale convective systems (MCSs), may persist for days, often regenerating convection daily. Long-lived MCVs can produce as much precipitation as a landfalling hurricane and lead to catastrophic flooding. The number of studies using multi-Doppler radar observations for validation of the kinematics, or three-dimensional (3-D) wind structure, of MCV genesis is limited. For this study, the Oklahoma City (KTLX) and Tulsa, Oklahoma (KINX) Weather Surveillance Radar – 1988 Doppler (WSR-88D) were used to examine the genesis of a long-lived MCV from 0000 to 0300 UTC on 11 June 2003. Traditional dual-Doppler techniques were used to determine the 3-D wind field. To relate MCV genesis within the associated larger MCS, time series of convective and stratiform precipitation, divergence, vertical vorticity, and vertical velocity were created for multiple levels within the MCS. The role of vertical vorticity generated in the convective region in MCV development was determined using vertical profiles of the terms in the vorticity tendency equation at 15 minute temporal resolution during the three hour period of investigation. The results of this study provide a detailed three hour examination for the initiation and early evolution of a long-lived MCV and can provide model validation of MCV generation.