Simulation of Polarimetric Phased Array Weather Radars

Polarimetric phased array radars (PPARs) are a rapidly developing area of research interest in weather radar. However, they present intrinsic challenges for calibration and operation. Foremost among these are the adverse effects of copolar radiation pattern mismatch as well as cross-polar fields on polarimetric measurement accuracy. Characterization of the impact these effects have on weather radar observations and the effectiveness of proposed methods for mitigation of those impacts can be time-consuming and costly if conducted using radar hardware. Furthermore, few operational PPARs exist to serve as testbeds. Alternatively, the effects of copolar and cross-polar fields can be studied using numerical simulations. In that regard, this work outlines a simulation method that allows for the characterization of PPAR performance and the prototyping of techniques to mitigate cross-polar biases. To achieve this, a simulation volume is populated by thousands of scattering centers, whose movement and scattering characteristics at any point in space and time are governed by a high-resolution numerical weather prediction model. Each of these scattering centers has its own individually calculated Doppler spectrum in both the horizontal (H) and vertical (V) polarizations. These spectra are used to determine instantaneous scattering parameters that are combined with a highly flexible radar system model in order to compose time-series signals in H and V. This simulation method is used to evaluate and compare the performance of several bias mitigation techniques that have been previously proposed

Quantitative Analysis of Rapid-Scan Phased Array Weather Radar Benefits and Data Quality Under Various Scan Conditions

Currently, NEXRAD provides weather radar coverage for the contiguous United States. It is believed that a replacement system for NEXRAD will be in place by the year 2040, where a major goal of such a system is to provide improved temporal resolution compared to the 5-10-min updates of NEXRAD. In this dissertation, multiple projects are undertaken to help achieve the goals of improved temporal resolution, and to understand possible scanning strategies and radar designs that can meet the goal of improved temporal resolution while either maintaining (or improving) data quality. Chapter 2 of this dissertation uses a radar simulator to simulate the effect of various scanning strategies on data quality. It is found that while simply reducing the number of pulses per radial decreases data quality, other methods such as beam multiplexing and radar imaging/digital beamforming offer significant promise for improving data quality and/or temporal resolution. Beam multiplexing is found to offer a speedup factor of 1.7-2.9, while transmit beam spoiling by 10 degrees in azimuth can offer speedup factors up to ~4 in some regions. Due to various limitations, it is recommended that these two methods be used judiciously for rapid-scan applications. Chapter 3 attempts to quantify the benefits of a rapid-scan weather radar system for tornado detection. The first goal of Chapter 3 is to track the development of a common tornado signature (tornadic debris signature, or TDS) and relate it to developments in tornado strength. This is the first study to analyze the evolution of common tornado signatures at very high temporal resolution (6 s updates) by using a storm-scale tornado model and a radar emulator. This study finds that the areal extent of the TDS is correlated with both debris availability and with tornado strength. We also find that significant changes in the radar moment variables occur on short (sub-1-min) timescales. Chapter 3 also shows that the calculated improvement in tornado detection latency time (137-207 s) is greater than that provided by theory alone (107 s). Together, the two results from Chapter 3 emphasize the need for sub-1-min updates in some applications such as tornado detection. The ability to achieve these rapid updates in certain situations will likely require a combination of advanced scanning strategies (such as those mentioned in Chapter 2) and adaptive scanning. Chapter 4 creates an optimization-based model to adaptively reallocate radar resources for the purpose of improving data quality. This model is primarily meant as a proof of concept to be expanded to other applications in the future. The result from applying this model to two real-world cases is that data quality is successfully improved in multiple areas of enhanced interest, at the expense of worsening data quality in regions where data quality is not as important. This model shows promise for using adaptive scanning in future radar applications. Together, these results can help the meteorological community understand the needs, challenges, and possible solutions to designing a replacement system for NEXRAD. All of the techniques studied herein either rely upon (or are most easily achieved by) phased array radar (PAR), which further emphasizes the utility of PAR for achieving rapid updates with sufficient data quality. It is hoped that the results in this dissertation will help guide future decisions about requirements and design specifications for the replacement system for NEXRAD

Signal Processing Techniques and Concept of Operations for Polarimetric Rotating Phased Array Radar

The Weather Surveillance Radar 1988 Doppler (WSR-88D) network has been operational for over 30 years and is still the primary observational instrument employed by the National Weather Service (NWS) forecasters to support their critical mission of issuing severe weather warnings and forecasts in the United States. Nevertheless, the WSR-88Ds have exceeded their engineering design lifespan and are projected to reach the end of operational lifetime by 2040. Technological limitations may prevent the WSR-88D to meet demanding functional requirements for future observational needs. The National Oceanic and Atmospheric Administration (NOAA) has started considering radar systems with advanced capabilities for the eventual replacement of the WSR-88D. Unique and flexible capabilities offered by Phased Array Radar (PAR) technology support the required enhanced weather surveillance strategies that are envisioned to improve the weather radar products, making PAR technology an attractive candidate for the next generation of weather radars. If PAR technology is to replace the operational WSR-88D, important decisions must be made regarding the architecture that will be needed to meet the functional requirements. A four-faced planar PAR (4F-PAR) is expected to achieve the requirements set forth by NOAA and the NWS, but deploying and maintaining an operational network of these radars across the U.S. will likely be unaffordable. A more affordable alternative radar system is based on a single-face Rotating PAR (RPAR) architecture, which is capable of exceeding the functionality provided by the WSR-88D network. This dissertation is focused on exploring advanced RPAR scanning techniques in support of meeting future radar functional requirements. A survey of unique RPAR capabilities is conducted to determine which ones could be exploited under an RPAR Concept of Operations (CONOPS). Three capabilities are selected for further investigation: beam agility, digital beamforming, and dwell flexibility. The RPARs beam agility is exploited to minimize the beam smearing that results from the rotation of the antenna system over the collection of samples in the coherent processing interval. The use of digital beamforming is investigated as a possible way to reduce the scan time and/or the variance of estimates. The RPAR's dwell flexibility capability is explored as a possible way to tailor the scan to meteorological observations with the goal of improving data quality. Three advanced RPAR scanning techniques are developed exploiting these capabilities, and their performance in support of meeting the radar functional requirements is quantified. The proposed techniques are implemented on the Advanced Technology Demonstrator (ATD), a dual-polarization RPAR system at the National Severe Storms Laboratory (NSSL) in Norman, OK. Data collection experiments are conducted with the ATD to demonstrate the performance of the proposed techniques for dual-polarization observations. Results are verified by quantitatively comparing fields of radar-variable estimates produced using the proposed RPAR techniques with those produced by a well-known collocated WSR-88D radar simultaneously collecting data following an operational Volume Coverage Pattern (VCP). The techniques introduced are integrated to operate simultaneously, and used to design an RPAR CONOPS that can complete a full volume scan in about one minute, while achieving other demanding functional requirements. It is expected that the findings in this dissertation will provide valuable information that can support the design of the future U.S. weather surveillance radar network

Remote sensing and image interpretation

A textbook prepared primarily for use in introductory courses in remote sensing is presented. Topics covered include concepts and foundations of remote sensing; elements of photographic systems; introduction to airphoto interpretation; airphoto interpretation for terrain evaluation; photogrammetry; radiometric characteristics of aerial photographs; aerial thermography; multispectral scanning and spectral pattern recognition; microwave sensing; and remote sensing from space

The LANDSAT Tutorial Workbook: Basics of Satellite Remote Sensing

Most of the subject matter of a full training course in applying remote sensing is presented in a self-teaching mode in this how-to manual which combines a review of basics, a survey of systems, and a treatment of the principles and mechanics of image analysis by computers, with a laboratory approach for learning to utilize the data through practical experiences. All relevant image products are included

Muscle activation patterns in shoulder impingement patients

Introduction: Shoulder impingement is one of the most common presentations of shoulder joint problems 1. It appears to be caused by a reduction in the sub-acromial space as the humerus abducts between 60o -120o – the 'painful arc'. Structures between the humeral head and the acromion are thus pinched causing pain and further pathology 2. Shoulder muscle activity can influence this joint space but it is unclear whether this is a cause or effect in impingement patients. This study aimed to observe muscle activation patterns in normal and impingement shoulder patients and determine if there were any significant differences. Method: 19 adult subjects were asked to perform shoulder abduction in their symptomatic arm and non-symptomatic. 10 of these subjects (age 47.9 ± 11.2) were screened for shoulder impingement, and 9 subjects (age 38.9 ± 14.3) had no history of shoulder pathology. Surface EMG was used to collect data for 6 shoulder muscles (Upper, middle and lower trapezius, serratus anterior, infraspinatus, middle deltoids) which was then filtered and fully rectified. Subjects performed 3 smooth unilateral abduction movements at a cadence of 16 beats of a metronome set at 60bpm, and the mean of their results was recorded. T-tests were used to indicate any statistical significance in the data sets. Significance was set at P<0.05. Results: There was a significant difference in muscle activation with serratus anterior in particular showing a very low level of activation throughout the range when compared to normal shoulder activation patterns (<30%). Middle deltoid recruitment was significantly reduced between 60-90o in the impingement group (30:58%).Trends were noted in other muscles with upper trapezius and infraspinatus activating more rapidly and erratically (63:25%; 60:27% respectively), and lower trapezius with less recruitment (13:30%) in the patient group, although these did not quite reach significance. Conclusion: There appears to be some interesting alterations in muscle recruitment patterns in impingement shoulder patients when compared against their own unaffected shoulders and the control group. In particular changes in scapula control (serratus anterior and trapezius) and lateral rotation (infraspinatus), which have direct influence on the sub-acromial space, should be noted. It is still not clear whether these alterations are causative or reactionary, but this finding gives a clear indication to the importance of addressing muscle reeducation as part of a rehabilitation programme in shoulder impingement patients

Nutritional quality and digestibility of maize hybrid plants for silage. Life sciences in dialogue of generations: connections between universities, academia and business

In order to assess the silage potential of maize hybrids, the nutritional quality and the enzymatic in vitro digestibility of five local maize hybrids (ZP 707, ZP 7357, ZP 7072, ZP 7777, and ZP 6263) was tested in the laboratory of the Group for Food Technology and Biochemistry of the Maize Research Institute "Zemun Polje". The hybrids were grown at a total of four locations, one in Srem (Autonomous Province of Vojvodina) and three in Central Serbia. The hybrid 7001 was used as a standard. The selection of hybrids for this research was made on the basis of the actuality of individual hybrids and the market orientation of the Maize Research Institute. The following properties were investigated: dry matter content, lignocellulose fiber content, and in vitro dry matter digestibility of the whole plant. According to the achieved results, it can be concluded that hybrids ZP 707, ZP 7357, followed by ZP 7777 proved to be the maize genotypes highly preferable for the production of silage. All tested hybrids achieved better results than the standard in most locations. Hybrid ZP 707 on average had the highest in vitro dry matter digestibility (61.43 ± 1.86%), as well as the lowest content of all lignocellulosic fibers (NDF-52.76%, ADF-24.40%, ADL-2.58, hemicellulose-28.36, and cellulose-21.82%), which all indicates its potential as a silage maize form suitable for cultivation in different agro-ecological conditions. In terms of digestibility and dry matter content, the ZP 707 hybrid can be singled out as the most stable, i.e. it is appropriate for growing both in lowland areas and at higher altitudes. ZP 6263 proved to be the most inferior hybrid at most locations, while based on in vitro digestibility and dry matter content, ZP 7072 hybrid varied the most. The digestibility of the whole plant was negatively affected by the higher content of primarily lignin (ADL), followed by ADF and cellulose fraction share. Although it is optimal to harvest silage maize in the waxy maturity stage of grain ripeness, when the dry matter content of the whole plant is in the range between 30 and 35%, the harvest time in some hybrids in some locations was significantly exceeded, which affected the results of dry matter digestibility. The findings obtained in this study can be highly useful for future breeding programs directed toward creating new and improved silage maize hybrids

Aerospace medicine and biology: A continuing bibliography with indexes (supplement 396)

This publication is a cumulative index to the abstracts contained in the Supplements 385 through 395 of Aerospace Medicine and Biology: A Continuing Bibliography. It includes seven indexes: subject, personal author, corporate source, foreign technology, contract number, report number, and accession number