Download or read book Improvement of Geophysical Model Functions for Radar based Ocean Surface Currents Measurements written by Shadi Aslebagh and published by . This book was released on 2018 with total page 98 pages. Available in PDF, EPUB and Kindle. Book excerpt: My objective in this research work is to improve the quality of ocean surface current measurements using synthetic aperture radars. I will do this by including an improved, physics-based model in the algorithm that inverts the radar data to estimate ocean currents. Although the ocean winds geophysical model functions used by scatterometers are mature, there is significant deficiency in knowledge of the ocean surface current geophysical model function; my research addresses this deficiency. In the first chapter of this thesis, I discuss the importance of ocean surface currents, and various techniques to measure them. Following that introduction, in chapter 2, I introduce the microwave radar system, which I used to collect microwave data for this research work. The corresponding flight experiments for microwave data collection are also described in this chapter. In chapter 3, the surface current estimation method is discussed and few samples of retrieved surface current components are presented. Chapter 4 introduces a physics-based Doppler model, M4S, which is used to improve the surface current geophysical model function. First, I run the model for different cases and compare the model’s outputs with radar measurements to evaluate the existing model. In chapter 5, in order to improve surface current geophysical model function, I incorporate model’s output to the geophysical retrieval algorithm and present the output of the retrieval algorithm. Eventually, in chapter 6, I will implement improvement to the model, which ultimately results in improvement of surface current geophysical model functions. Chapter 6 includes the results, discussions and suggestions for future work.

Download or read book Coastal Ocean Dynamics Applications Radar written by Thomas Martin Georges and published by . This book was released on 1985 with total page 352 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Sea Surface Roughness Observed by High Resolution Radar written by Atsushi Fujimura and published by MDPI. This book was released on 2019-10-25 with total page 202 pages. Available in PDF, EPUB and Kindle. Book excerpt: Changes in sea surface roughness are usually associated with a change in the sea surface wind field. This interaction has been exploited to measure sea surface wind speed by scatterometry. A number of features on the sea surface associated with changes in roughness can be observed by synthetic aperture radar (SAR) because of the change in Bragg backscatter of the radar signal by damping of the resonant ocean capillary waves. With various radar frequencies, resolutions, and modes of polarization, sea surface features have been analyzed in numerous campaigns, bringing various datasets together, thus allowing for new insights into small-scale processes at a larger areal coverage. This Special Issue aims at investigating sea surface features detected by high spatial resolution radar systems, such as SAR.

Download or read book Measuring Ocean Currents written by Antony Joseph and published by Newnes. This book was released on 2013-08-12 with total page 447 pages. Available in PDF, EPUB and Kindle. Book excerpt: Measuring Ocean Currents: Tools, Technologies, and Data covers all major aspects of ocean current measurements in view of the implications of ocean currents on changing climate, increasing pollution levels, and offshore engineering activities. Although more than 70% of the Earth is covered by ocean, there is limited information on the countless fine- to large-scale water motions taking place within them. This book fills that information gap as the first work that summarizes the state-of-the-art methods and instruments used for surface, subsurface, and abyssal ocean current measurements. Readers of this book will find a wealth of information on Lagrangian measurements, horizontal mapping, imaging, Eulerian measurements, and vertical profiling techniques. In addition, the book describes modern technologies for remote measurement of ocean currents and their signatures, including HF Doppler radar systems, satellite-borne sensors, ocean acoustic tomography, and more. Crucial aspects of ocean currents are described in detail as well, including dispersion of effluents discharged into the sea and transport of beneficial materials—as well as environmentally hazardous materials—from one region to another. The book highlights several important practical applications, showing how measurements relate to climate change and pollution levels, how they affect coastal and offshore engineering activities, and how they can aid in tsunami detection. Coverage of measurement, mapping and profiling techniques Descriptions of technologies for remote measurement of ocean currents and their signatures Reviews crucial aspects of ocean currents, including special emphasis on the planet-spanning thermohaline circulation, known as the ocean's "conveyor belt," and its crucial role in climate change

Download or read book Advanced Ocean Surface Measurements with HF Radar written by and published by . This book was released on 1997 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: HF surface wave radar for ocean wave and current measurements began with collaborative work at Stanford University and Scripps Institution of Oceanography in the late 1960's. Two of the participants in this project (Drs. Teague and Vesecky) have worked with HF radar observations of the ocean since these early experiments. Under this grant a new HF radar design was begun and some prototype construction completed. This work led to construction of a full scale prototype that is now being tested over Monterey Bay, California from a field site kindly provided at the Long Marine Laboratory of the University of California at Santa Cruz. Initial results, including radial current field maps at four frequencies and variations of currents with time, were presented at the American Geophysical Union Fall Meeting in San Francisco, December, 1996. This final report is a presentation of results under the funding from ONR grant N00014-94-1-0371. It contains an overview of the radar design and its implementation in hardware as well as some preliminary results on vertical shear in the surface current field over Monterey Bay CA.

Download or read book Oceanobs 19 An Ocean of Opportunity Volume II written by Tong Lee and published by Frontiers Media SA. This book was released on 2020-12-31 with total page 629 pages. Available in PDF, EPUB and Kindle. Book excerpt: This eBook is a collection of articles from a Frontiers Research Topic. Frontiers Research Topics are very popular trademarks of the Frontiers Journals Series: they are collections of at least ten articles, all centered on a particular subject. With their unique mix of varied contributions from Original Research to Review Articles, Frontiers Research Topics unify the most influential researchers, the latest key findings and historical advances in a hot research area! Find out more on how to host your own Frontiers Research Topic or contribute to one as an author by contacting the Frontiers Editorial Office: frontiersin.org/about/contact.

Download or read book The Norwegian Coastal Current written by and published by Fagbokforlaget. This book was released on 2007 with total page 170 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Norwegian coastal current originates primarily from the freshwater outflow from the Baltic and the freshwater runoff from Norway. It flows northwards along the coast of Norway as a low-salinity current. This coastal region is the spawning ground for a number of important oceanic fish stocks, and the physical environment has an impact on the recruitment, growth, and geographical distribution of these stocks. In the late 1920s and early 1930s, the Institute of Marine Research in Norway established a coastal oceanographic observation system. This continued to evolve, and its core elements are still in operation. Drawing on the results generated by this observation system, as well as by other coastal studies, this book reviews the current understanding of the physical/chemical conditions in the Norwegian coastal current in such a way as to make the material more easily accessible to non-specialists. A series of chapters introduces readers to the geography, currents, water masses, and the temporal and spatial variability of the Norwegian coastal current. Interannual fluctuations in physical conditions are most likely to be the prime cause of ecosystem variability. The editor hopes that this book will act as a point of departure for a future summary of the ecology of Norwegian coastal waters.

Download or read book High frequency Radar Measurements of Coastal Ocean Surface Currents written by Daniel Martin Fernandez and published by . This book was released on 1993 with total page 382 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Encyclopedia of Remote Sensing written by Eni Njoku and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This first encyclopaedic reference on remote sensing describes the concepts, techniques, instrumentation, data analysis, interpretation, and applications of remote sensing, both airborne and space-based. Scientists, engineers, academics, and students can quickly access answers to their reference questions and direction for further study.

Download or read book Remote Sensing of Ocean Surface Current and Current Shear by HF Backscatter Radar written by Eng-Chong Ha and published by . This book was released on 1979 with total page 158 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Doppler spectrum of radar return from the sea at HF contains two narrow lines displaced upward and downward from the carrier frequency, resulting from backscatter off ocean surface waves moving toward and away from the radar, respectively. These Bragg lines indicate resonant backscatter which occurs for the ocean waves of length one-half the radio wavelength. The phase velocity of these gravity waves consists of two components; the first is determined by the wavelength and the second by the current component in the direction of wave propagation averaged over depth with an exponential weighting function that has a characteristic scale proportional to the wavelength. The Doppler shift of the radar carrier is determined by the wave phase velocity. Its variation with carrier frequency is thus related to the vertical profile of the current component in the radar direction by a Laplace transform; therein lies the principle of radio measurement of ocean current and its vertical shear. Radio backscatter experiments to verify the feasibility of such measurements were conducted using the radar operating at four frequencies covering the range from 3 to 30 MHz. The depth-averaged radial current deduced from the centroid of the Doppler-shifted sea echo experiments at 6.8, 13.3, 21.7, and 29.8 MHz showed fluctuations on the order of 1 cm/sec superimposed on temporal trends that reached maximum values of about 40 cm/sec. It is concluded that multifrequency backscatter ground-wave radar at HF constitutes a powerful technique for mapping current and its vertical profile in the top few meters of the ocean.

Download or read book Ocean Remote Sensing Technologies written by Weimin Huang and published by IET. This book was released on 2021-12-17 with total page 654 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book provides a systematic introduction to the principles, state-of-the-art methods and applications of high frequency surface/sky wave radar and microwave marine radar, as well as an exploration of ongoing challenges in the field. It is a valuable resource for the radar and remote sensing communities.

Download or read book Use of Empirical Orthogonal Functions in the Analysis of OSCR Ocean Surface Current Radar Measurements written by B. Ng and published by . This book was released on 1992 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Radar Imaging of the Ocean Waves written by Mikhail B. Kanevsky and published by Elsevier. This book was released on 2008-09-15 with total page 207 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is dedicated to studying the ocean with radar tools, in particular, with space radars. Being intended mainly for the scientists preoccupied with the problem (as well as senior course students), it concentrates and generalizes the knowledge scattered over specialized journals. The significant part of the book contains the results obtained by the author. Systematically collects and describes the approaches used by different laboratories and institutions Deals with the physics of radar imagery and specifically with ocean surface imagery Useful for students and researchers specializing in the area of ocean remote sensing using airborne or space-borne radars, both SAR and RAR

Download or read book Distributed Space Missions for Earth System Monitoring written by Marco D'Errico and published by Springer Science & Business Media. This book was released on 2012-09-14 with total page 682 pages. Available in PDF, EPUB and Kindle. Book excerpt: This title analyzes distributed Earth observation missions from different perspectives. In particular, the issues arising when the payloads are distributed on different satellites are considered from both the theoretical and practical points of view. Moreover, the problems of designing, measuring, and controlling relative trajectories are thoroughly presented in relation to theory and applicable technologies. Then, the technological challenges to design satellites able to support such missions are tackled. An ample and detailed description of missions and studies complements the book subject.

Download or read book Development and Evaluation of New Algorithms for the Retrieval of Wind and Internal Wave Parameters from Shipborne Marine Radar Data written by Björn Lund and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The goal of this work is to develop and evaluate techniques for the retrieval of wind and internal wave (IW) information from marine X-band radar data. While ocean wind measurements are crucial for the transfer of energy and momentum across the air-sea interface, IWs play an important role in tidal energy transport. Marine radars work by transmitting microwave energy from a rotating antenna that also measures the backscatter. The radar backscatter from the sea surface is controlled by the wind-generated small ripple waves through the Bragg-scattering mechanism. Surface winds are thus the dominant factor for generating the radar backscatter. The varying surface current fields associated with IWs interact with the ripples, generating rough convergent and smooth divergent zones. Radars are capable of imaging such IW-induced surface signatures as bands of enhanced and weakened backscatter. The advantage of radar-based wind information is that it is obtained from a large area around the instrument. Marine radar wind data are therefore much less likely to be affected by platform-induced air flow distortions than in-situ measurements. Previous investigators have already demonstrated marine radar's suitability as a wind sensor [31, 30], however, these works have been limited to fixed-platform data. Here, the focus lies on shipborne marine radar data. Such data present the challenge that the existing wind streak-based approach for retrieving wind directions cannot be directly applied. This is because the wind streak signal may become obscured by the horizontal ship motion, since wind streaks become visible only after averaging over a sequence of radar images. In addition, moving platforms face a greater variability of conditions, which may further complicate a radar-based wind retrieval. Grazing incidence HH-polarized (horizontal transmit and receive) X-band radar data exhibit a single intensity peak in upwind direction. To retrieve the wind direction, this work proposes a least-squares fit technique that identifies the upwind peak in the range-averaged backscatter dependency on the antenna look direction. This technique requires no motion correction and is therefore well-suited for shipborne data. In addition, it functions well even if sections of the radar field of view are masked. An empirical model function is derived to retrieve the wind speed from the mean radar backscatter intensity. Data from the U.S. Office of Naval Research (ONR) Impact of Typhoons on the Ocean in the Pacific (ITOP) experiment are used for a comparison between radar-based wind estimates and anemometer measurements. The two data sets show good agreement. In addition, this work proposes a technique that uses geolocated marine radar data to extract wind streak information through a localized Radon transform. To compare streak- and upwind peak-based wind direction retrieval techniques, fixed and moving platform marine radar data from the ONR-sponsored High Resolution Air-Sea Interaction (Hi-Res) experiment are used. Wind directions obtained using the upwind peak method show a better agreement with the reference data than those obtained from the wind streaks. The difference between fixed and moving platform for the wind streak approach indicates that the image geolocation affects the wind retrieval negatively. Standard deviations as low as 6.0° and 0.42 m/s for the comparison between radar-based and reference wind data show that marine radars can yield highly reliable wind estimates. Regarding IWs, a new fully automated tool to retrieve IW signatures from marine radar image sequences is developed and applied to data collected during ONR's Non-Linear Internal Wave Initiative / Shallow Water '06 experiment (NLIWI/SW06). Marine radars have the advantage over satellite systems that their high temporal resolution enables the study of the IW evolution. The proposed technique employs our knowledge about the wind dependency of the radar backscatter to correct for the image ramp, i.e. the return signal's dependency on range and antenna look direction. The ramp-corrected radar images are then geolocated and averaged, which greatly enhances the IW signal. By determining the IW group velocity and correcting for it before the radar images are averaged, the IW signal is further enhanced. Such pre-processing enables a reliable retrieval of IW surface signatures by clustering local peaks and troughs, and tracking those clusters through time. This work also includes a detailed analysis of data collected during the tracking of a particularly energetic IW. The radar-derived time series of IW speed, direction, and soliton maps yield unique information about the IW's spatio-temporal evolution, including evidence of wave-wave interactions. In addition, it is demonstrated that marine radar data can be used to retrieve information about the interior ocean dynamics associated with the IW. The IW-induced backscatter modulation is correlated with the measured surface current gradients and IW amplitudes. Alternatively, results are shown where IW amplitudes were derived from the distances between positive and negative radar backscatter peaks. This approach was first introduced by Xue et al. [132] and is based on an extended Korteweg-de-Vries (eKdV) equation. This approach has the advantage that it is much less dependent on the prevailing wind conditions. To summarize, the marine radar backscatter dependency on wind is analyzed, and new wind retrieval techniques from shipborne radar data are proposed. The gained knowledge on the backscatter's wind dependency is then applied to marine radar data containing IW surface signatures. This work proposes a new methodology for retrieving these signatures and uses the resulting IW soliton maps to derive information about the IW-associated interior ocean dynamics.

Download or read book Earth Resources written by and published by . This book was released on 1983 with total page 758 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 456 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.