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This 2001 book provides a detailed introduction to the principles of Doppler and polarimetric radar, focusing in particular on their use in the analysis of weather systems. The design features and operation of practical radar systems are highlighted throughout the book in order to illustrate important theoretical foundations. The authors begin by discussing background topics such as electromagnetic scattering, polarization, and wave propagation. They then deal in detail with the engineering aspects of pulsed Doppler polarimetric radar, including the relevant signal theory, spectral estimation techniques, and noise considerations. They close by examining a range of key applications in meteorology and remote sensing. The book will be of great use to graduate students of electrical engineering and atmospheric science as well as to practitioners involved in the applications of polarimetric radar systems.
Weather radar is a vital instrument for observing the atmosphere to help provide weather forecasts and issue weather warnings to the public. The current Next Generation Weather Radar (NEXRAD) system provides Doppler radar coverage to most regions of the United States (NRC, 1995). This network was designed in the mid 1980s and deployed in the 1990s as part of the National Weather Service (NWS) modernization (NRC, 1999). Since the initial design phase of the NEXRAD program, considerable advances have been made in radar technologies and in the use of weather radar for monitoring and prediction. The development of new technologies provides the motivation for appraising the status of the current weather radar system and identifying the most promising approaches for the development of its eventual replacement. The charge to the committee was to determine the state of knowledge regarding ground-based weather surveillance radar technology and identify the most promising approaches for the design of the replacement for the present Doppler Weather Radar. This report presents a first look at potential approaches for future upgrades to or replacements of the current weather radar system. The need, and schedule, for replacing the current system has not been established, but the committee used the briefings and deliberations to assess how the current system satisfies the current and emerging needs of the operational and research communities and identified potential system upgrades for providing improved weather forecasts and warnings. The time scale for any total replacement of the system (20- to 30-year time horizon) precluded detailed investigation of the designs and cost structures associated with any new weather radar system. The committee instead noted technologies that could provide improvements over the capabilities of the evolving NEXRAD system and recommends more detailed investigation and evaluation of several of these technologies. In the course of its deliberations, the committee developed a sense that the processes by which the eventual replacement radar system is developed and deployed could be as significant as the specific technologies adopted. Consequently, some of the committee's recommendations deal with such procedural issues.
With their images practically ubiquitious in the daily media, weather radar systems provide data not only for understanding weather systems and improving forecasts (especially critical for severe weather), but also for hydrological applications, flood warnings and climate research in which ground verification is needed for global precipitation measurements by satellites. This book offers an accessible overview of advanced methods, applications and modern research from the European perspective. An extensive introductory chapter summarizes the principles of weather radars and discusses the potential of modern radar systems, including Doppler and polarisation techniques, data processing, and error-correction methods. Addressing both specialist researchers and nonspecialists from related areas, this book will also be useful for graduate students planning to specialize in this field
Improved measurements of precipitation will aid our understanding of the role of latent heating on global circulations. Spaceborne meteorological sensors such as the planned precipitation radar and microwave radiometers on the Tropical Rainfall Measurement Mission (TRMM) provide for the first time a comprehensive means of making these global measurements. Pre-TRMM activities include development of precipitation algorithms using existing satellite data, computer simulations, and measurements from limited aircraft campaigns. Since the TRMM radar will be the first spaceborne precipitation radar, there is limited experience with such measurements, and only recently have airborne radars become available that can attempt to address the issue of the limitations of a spaceborne radar. There are many questions regarding how much attenuation occurs in various cloud types and the effect of cloud vertical motions on the estimation of precipitation rates. The EDOP program being developed by NASA GSFC will provide data useful for testing both rain-retrieval algorithms and the importance of vertical motions on the rain measurements. The purpose of this report is to describe the design and development of real-time embedded parallel algorithms used by EDOP to extract reflectivity and Doppler products (velocity, spectrum width, and signal-to-noise ratio) as the first step in the aforementioned goals. Nicholson, Shaun R. Unspecified Center AIRBORNE/SPACEBORNE COMPUTERS; COMPUTER SYSTEMS DESIGN; DOPPLER RADAR; METEOROLOGICAL INSTRUMENTS; METEOROLOGICAL RADAR; PRECIPITATION (METEOROLOGY); RADAR MEASUREMENT; SIGNAL PROCESSING; AIRBORNE EQUIPMENT; AIRBORNE RADAR; ALGORITHMS; COMPUTERIZED SIMULATION; PARALLEL PROCESSING (COMPUTERS); REAL TIME OPERATION; SIGNAL TO NOISE RATIOS; SPACECRAFT INSTRUMENTS; SUPERHIGH FREQUENCIES...
This Ph.D dissertation focuses on applications of a mobile high resolution X-band polarimetric Doppler weather radar observations in quantitative rainfall and microphysical estimation. X-band tends to be an attractive radar frequency for hydrologists and hydrometeorologists who are more interesting in high-resolution measurements over small watersheds. However, the drawback with X-band radar is severe attenuation of the electromagnetic signal in significant rainfall, which affects the radar observations and introduces errors in rainfall estimation. The major advantage of the polarimetric weather radar is that it has the ability to transmit and receive both horizontal and vertical polarization. This capability introduces two radar measurements apart from the horizontal reflectivity (ZH). These are the differential reflectivity (ZDR), which is the ratio of horizontal (H) to vertical (V) polarization and the differential phase shift (ΦDP), which is the difference in phase between the H and V polarization signals. This additional information helps to increase the correlation (r 2 > 0.95) between attenuation-corrected (National Observatory of Athens X-band polarimetric) XPOL versus the non-attenuated ZH and ZDR X-band parameters derived from (NCAR S-band polarimetric radar) S-Pol. Error statistics show that the selected algorithm with the least systematic error than the other methods and axial ratio models, converge to below 10% (50%) at path integrated attenuation (differential PIA) values greater than 10 dB (2.5 dB). Overall, the combined uncertainty in the estimation of specific and differential attenuation parameters represent about 28% (in ZH) and 38% (in ZDR). The first part of this thesis focuses on the development of an algorithm that corrects for rain-path attenuation. The second part of this thesis describes a methodology that estimates drop size distribution (DSD) from the attenuation-corrected radar measurements. Two algorithms that estimate the three-parameter 'normalized' Gamma DSD model are developed for X-band radar polarimetric observations and compared against S-Pol radar and disdrometer spectra observations. The constrained-gamma method is so named because of the constrained Î1⁄4-Λ relation and the "Î2" beta is so named because of the estimation of the mean axis ratio of drops. From the statistical analysis and comparisons of disdrometer spectra observations and S-Pol DSD retrievals, it is found that the Î2-method introduces errors from the use of KDP, while the constrained-method works reasonably well at low and high rain rates and provides relatively accurate retrieval of the DSD parameters. Error statistics show that the Î2-method introduces an additional 20% and 30% error in NW and Î1⁄4 while for the estimation of D 0 both algorithms have similar performance.
An interdisciplinary, easy-to-understand introduction, covering fundamental theory and practical applications. Featuring numerous operational examples, and interpretation of radar observations, this is a perfect resource for scientists and engineers working on or with radars, as well as senior undergraduate and graduate students.
Low-cost X-band radars are an emerging technology that offer significant advantages over traditional systems for weather remote sensing applications. X-band radars provide enhanced angular resolution at a fraction of the aperture size compared to larger, lower frequency systems. Because of their low cost and small form factor, these radars can now be integrated into more research and commercial applications. This work presents research and development activities using a low-cost, X-band (9410 MHz) Phase-Tilt Radar. The phase-tilt design is a novel phased array architecture that allows for rapid electronic scanning in azimuth and mechanical tilting in elevation, as a compromise between cost and performance. This work focuses on field studies and experiments in three meteorological applications. The first stage of research focuses on the real-world application of phased array radars in forest fire monitoring and observation. From April to May 2013, a phase-tilt radar was deployed to South Australia and underwent a field campaign to make polarimetric observations of prescribed burns within and around the Adelaide Hills region. Measurements show the real-time evolution of the smoke plume dynamics at a spatial and temporal resolution that has never before been observed with an X-band radar. This dissertation will perform data analysis on results from this field campaign. Results are compared against existing work, theories, and approaches. In the second stage of research, field experiments are performed to assess the data quality of X-band phased array radars. Specifically, this research focuses on the measurement of and techniques to improve the variance of weather product estimators for dual-polarized systems. Variability in the radar products is a complicated relationship between the radar system specifications, scanning strategy, and the physics governing precipitation. Here, the variance of the radar product estimators is measured using standard radar scanning strategies employed in traditional mechanical antenna systems. Results are compared against adaptive scan strategies such as beam multiplexing and frequency diversity. This work investigates the improvement that complex scanning strategies offer in dual-polarized, X-band phased array radar systems. In the third stage of research, simulations and field experiments are conducted to investigate the performance benefits of adaptive scanning to optimize the data quality of radar returns. This research focuses on the development and implementation of a waveform agile and adaptive scanning strategy to improve the quality of weather product estimators. Active phased array radars allow radar systems to quickly vary both scan pointing angles and waveform parameters in response to real-time observations of the atmosphere. As an evolution of the previous research effort, this work develops techniques to adaptively change the scan pointing angles, transmit and matched filter waveform parameters to achieve a desired level of data quality. Strategies and techniques are developed to minimize the error between observed and desired data quality measures. Simulation and field experiments are performed to assess the quality of the developed strategies.
This thesis describes the deployment of MIRSL's X-band dual-polarization Phase-Tilt Weather Radar (PTWR) at the University of Texas at Arlington during spring 2014. While this radar has been used to observe weather in Western Massachusetts, more observations of severe weather were required to determine the limits of its abilities in sensing more rapidly evolving weather systems. This site was chosen also for its proximity to the Dallas-Fort Worth Urban Testbed Network set up by the Center for Collaborative Adaptive Sensing of the Atmosphere (CASA), which provided the ability to compare and calibrate the PTWR data against another well-documented X-band weather radar. A data processing pipeline was developed for converting raw PTWR data to NetCDF format, which allows for easy sharing and mapping of weather data. Finally, this is the first in-depth documentation of the PTWR system and specifically the roof-mounted setup utilized for this deployment.