共查询到20条相似文献，搜索用时 15 毫秒
1.
From August 1976 through December 1978, extremely low frequency (ELF) field strength and effective noise measurements were taken continuously in Connecticut and sporadically aboard operational submarines. This article summarizes the field strength measurements taken at both land (Connecticut) and sea (North Atlantic, Western Pacific) locations during January, March, April, and October 1977 and January/ February 1978. The main conclusion is that the average field strengths measured aboard the submarines (which were located at distances of 4-12 Mm from the Wisconsin Test Facility) are in excellent agreement with previous ELF measurements taken over similar paths. Anomalous ELF field strength variations were also correlated with geomagnetic activity. Interference between the direct and "round-the-world" paths was probably observed during the Western Pacific area daytime propagation period in early October 1977. ELF propagation effects were also observed during the February 13, 1978, significant solar particle event. 相似文献
2.
Ross N. Williams 《Marine Geodesy》2013,36(1):83-91
Abstract The concept of sensing oceanic parameters from space has been clearly demonstrated by the data from NASA's SEASAT. As the next step, a triagency team from NASA, NOAA, and DOD developed a program for a national system, the National Oceanic Satellite System (NOSS). The NOSS was to be an end‐to‐end system, a five‐year quasi‐operational demonstration to satisfy the most critical of the user agencies (NOAA and Navy) requirements for oceanographic data. Unfortunately, NOSS became an early victim of the Administration's efforts to reduce the Federal budget. The search for less costly (less capable) alternatives continues. In the meantime, the accuracy of our operational forecasts suffers and critical requirements go unsatisfied. 相似文献
3.
Yan-Shek Hoh 《Oceanic Engineering, IEEE Journal of》1984,9(3):164-178
This paper examines the extremely low frequency (ELF) radiation from a horizontal antenna in the earth-ionosphere waveguide. Attention is focused on the application to field predictions in the Navy's ELF program. The field expressions in the presence of an anisotropic ground are obtained by a heuristic approach based upon a linear relationship between the horizontal electric and magnetic field components. Phasing anomalies at the Wisconsin Test Facility (WTF) have been observed since 1974. A theoretical model of this phenomenon is derived on the basis of a mutual coupling mechanism between the two WTF antenna elements and characteristics observed in measured field strength data. The diurnal variation of the radiated field is studied in terms of the attenuation rate, phase velocity, and height of the ionospheric reflecting layers. The diffusivity characteristics of realistic ionosphere are analytically modeled. A comparison of the predicted field strength/phase with the measured data yields excellent agreement. 相似文献
4.
In the summer and fall of 2012, during the GLAD experiment in the Gulf of Mexico, the Consortium for Advanced Research on Transport of Hydrocarbon in the Environment (CARTHE) used several ocean models to assist the deployment of more than 300 surface drifters. The Navy Coastal Ocean Model (NCOM) at 1 km and 3 km resolutions, the US Navy operational NCOM at 3 km resolution (AMSEAS), and two versions of the Hybrid Coordinates Ocean Model (HYCOM) set at 4 km were running daily and delivering 72-h range forecasts. They all assimilated remote sensing and local profile data but they were not assimilating the drifter’s observations. This work presents a non-intrusive methodology named Multi-Model Ensemble Kalman Filter that allows assimilating the local drifter data into such a set of models, to produce improved ocean currents forecasts. The filter is to be used when several modeling systems or ensembles are available and/or observations are not entirely handled by the operational data assimilation process. It allows using generic in situ measurements over short time windows to improve the predictability of local ocean dynamics and associated high-resolution parameters of interest for which a forward model exists (e.g. oil spill plumes). Results can be used for operational applications or to derive enhanced background fields for other data assimilation systems, thus providing an expedite method to non-intrusively assimilate local observations of variables with complex operators. Results for the GLAD experiment show the method can improve water velocity predictions along the observed drifter trajectories, hence enhancing the skills of the models to predict individual trajectories. 相似文献
5.
The efforts to use GEOSAT data to refine an ice index that is applicable to widely varying ice conditions are detailed. The sea-ice mapping requirements, the present US Navy ice-index operational utilization, and ongoing and future work that promises to provide additional sea-ice measurement capabilities are discussed. Possibilities include discrimination among water, land, ice, combination water/ice, and water/land, as well as distinguishing various ice concentrations and possibly ice types. Coincident airborne passive microwave and synthetic-aperture-radar (SAR) data have been collected to test several methods which appear to be promising 相似文献
6.
From August 1976 through December 1978, extremely low frequency (ELF) field-strength and effective-noise measurements were taken continuously in Connecticut and sporadically aboard operational submarines. This paper summarizes the effective-noise measurements taken at both Connecticut and sea (North Atlantic, Norwegian Sea, South Atlantic equatorial area, Virgin Islands area, Hawaii area, Western Pacific, and Northwestern Pacific) locations during this period. The main conclusion is that there are often considerable differences in effective-noise levels measured at Connecticut and sea locations. The highest effective noise levels were measured in Connecticut during the summer months, while the lowest effective-noise levels were measured in the South Atlantic equatorial area during November. 相似文献
7.
The U.S. Navy has initiated a multidisciplinary research and development program to study the Effects of Sound on the Marine Environment (ESME). As part of this effort, the Naval Research Laboratory (NRL) is developing a software workbench for estimating the effects of cumulative sound exposure on marine mammals. This paper describes the workbench, and presents some preliminary simulation results. The workbench integrates data sets and computer models contributed by researchers in the areas of oceanography, underwater acoustic propagation, and marine mammal physiology and behavior. Models are incorporated for simulating animal movement, for estimating the received acoustic time series along an animal's track, and for predicting temporary threshold shifts (TTSs) induced by acoustic exposure. TTS predictions are shown to be highly dependent upon both the environmental variables and the movement of the marine mammals. 相似文献
8.
Extremely low frequency (ELF) electromagnetic waves have a remarkable ability to propagate with very little attenuation in the earth-ionosphere waveguide. The resulting fields are also able to propagate to moderately great depths in the ocean in spite of the higher conductivity of seawater. The principal drawback in the use of ELF for communication is the inherent inefficiency of the transmitting antenna. Indeed the waves do, however, penetrate to deeply submerged submarines when all other methods fail. This paper presents a tutorial overview on ELF propagation in the earth-ionosphere waveguide. Simple form approximate expressions (relating ELF propagation constants to realistic ionospheric conductivity profiles) are compared with experimentally derived results for both daytime and nighttime propagation conditions. Some anomalous ELF propagation results, along with their probable causes, are also discussed. 相似文献
9.
Electromagnetic waves at extremely low frequency (ELF) have a remarkable ability to propagate with very low attenuation in the space between the earth's surface and the ionosphere. The resulting fields also are able to propagate to moderately great depths in the ocean in spite of the high conductivity of sea water. The principal drawback in the use of such signals for communication is the inherent inefficiency of the transmitting antenna. But indeed the waves do penetrate to deeply submerged submarines when all other methods fail. This has been the principal motivation of the U.S. Navy's controversial Project Sanguine that envisages a huge antenna facility that could cover an area of 100 by 100 km. This project, now called Seafarer, has stimulated a great deal of research on how ELF waves (in the range from about 1- 1000 Hz) propagate. We review here some of the fascinating developments in this field. Actually, the early investigations of Nicola Tesla have a striking similarity to Project Sanguine. Tesla's prophetic lectures and articles provide an interesting historical perspective to the later developments that have spanned over 70 years. After sketching some of the early history of the subject, we outline the theoretical and physical bases of the propagation phenomena. While the basic concept of the earth-ionosphere waveguide is relatively simple, the physics of the interaction with the ionospheric plasma is complicated, particularly during disturbed conditions. 相似文献
10.
Philip Y. Chu Gregg A. Jacobs M. Kemal Cambazoglu Robert S. Linzell 《Marine Geodesy》2013,36(4):399-428
In this paper, we discuss the validation of water level and current predictions from three coastal hydrodynamic models and document the resource and operational requirements for each modeling system. The ADvanced CIRCulation Model (ADCIRC), the Navy Coastal Ocean Model (NCOM), and Delft3D have been configured and validated for the Chesapeake Bay region during a Navy exercise. Water level predictions are compared with a NOAA/NOS water level gauge at the Chesapeake Bay Bridge Tunnel location while current predictions are validated with Acoustic Doppler Profiler (ADP) measurement records at three locations in the lower Chesapeake Bay. Statistical metrics such as correlation coefficient and root mean square error (RMSE) are computed. Both the vertically-integrated currents and currents at varying water depths are compared as well. The model-data comparisons for surface elevation indicate all three models agreed well with water level gauge data. The two-dimensional version of ADCIRC, ADCIRC2D, and NCOM yield better statistics, in terms of correlation and RMSE, than Delft3D. For vertically-integrated currents, ADCIRC2D has the smallest RMSE at Thimble Shoal and Naval Station locations while NCOM has the smallest RMSE at Cape Henry. For the horizontal currents over the water column, the fully three-dimensional, baroclinic ADCIRC model, ADCIRC3D, and NCOM both showed better agreement with the ADP measurements. 相似文献
11.
12.
Vronique Cochin Vincent Mariette Pierre Broche Ren Garello 《Oceanic Engineering, IEEE Journal of》2006,31(4):885-893
Performance and operational feasibility of very high-frequency (VHF) Doppler radar have been demonstrated in a region dominated by strong tidal currents. An analysis of remote measurements of sea surface currents acquired by Courants de Surface MEsureacutes par Radar (COSMER)-pulsed Doppler radar during Evaluation et Preacutevision de l'Environnement Littoral (EPEL) experiment (supported by the French Navy) is presented in this paper. The VHF COSMER radar was deployed to provide continuous sea surface current measurements within an area of about 25 km times 25 km in the Normand Breton Gulf, France. This paper presents VHF measurement comparisons with observations such as acoustic Doppler current profiler (ADCP), as well as comparisons with numerical model TELEMAC 2-D. Results of tidal waves extraction, using harmonic analysis and residual currents, are shown in this paper. We also present a case where radar method is limited, due to the presence of additional peaks in the Doppler spectrum 相似文献
13.
The 60-Hz electromagnetic fields in the Atlantic Ocean off Montauk Point, NY, and from Block Island Sound to the harbor in New London, CT, have been measured to determine the levels of interference to an extremely low frequency (ELF) receiver. Such data are needed to specify how close to the coastline an ELF receiver can come before 60-Hz external interference will degrade system performance. The data indicate that degradation to the ELF receiver from 60-Hz external interference will not occur offshore, but may occur within the confines of New London Harbor. 相似文献
14.
Satellite altimetry has become an important discipline in the development of sea-state forecasting or more generally in operational oceanography. Météo-France Marine and Oceanography Division is much involved in altimetry, in which it is also one of the main operational customers. Sea-state forecasts are produced every day with the help of numerical models assimilating Fast Delivery Product altimeter data from ESA ERS-2 satellite, available in real-time (3–5 h). These forecasts are transmitted to seamen as part of safety mission of persons and properties, or specific assistance for particular operations. With the launch of ENVISAT (from ESA, launched on 1 March 2002, to take over the ERS mission) and JASON-1 (from CNES/NASA, launched on 7 December 2001, successor of TOPEX/Poseidon), we have an unprecedented opportunity of improved coverage with the availability in quasi-real-time of data from several altimeters. The objective of this study is to evaluate the impact of using multisources of altimeter data in real-time, to improve wave model analyses and forecasts, at global scale. Since July 2003, Météo-France injects the wind/wave JASON-1 Operational Sensor Data Record on the WMO Global Transmitting System, making them available in near real-time to the international meteorological community. Similarly, fast delivery altimeter data of ENVISAT will improve coverage and contribute to the constant progress of marine meteorology. For this purpose, significant wave height time series were generated using the Wave Model WAM and the assimilation of altimeter wave heights from two satellites ERS-2 and JASON-1. The results were then compared to Geosat Follow-On (GFO, U.S. Navy Satellite) and moored buoy wave data. It is shown that the impact of data assimilation, when two (ERS-2 and JASON-1) or three (ERS-2 with JASON-1 and GFO) sources of data are used instead of one (ERS-2), in term of significant wave height, is larger in wave model analyses but smaller in wave model forecasts. However, there is no improvement in terms of wave periods, both in the analysis and forecast periods. 相似文献
15.
Remote sensing with the JINDALEE skywave radar 总被引：1，自引：0，他引：1
The JINDALEE skywave radar is being developed primarily for defense surveillance of Australia's Exclusive Economic Zone (EEZ), but its remote-sensing potential has long been recognized. Studies which commenced in 1974 led to successful measurements of sea-state and inferred surface wind fields in 1977-78 using a prototype radar; the current radar has been observing the Eastern Indian Ocean region since 1982. The JINDALEE radar is now linked to the Australian Bureau of Meteorology regional forecasting centers by a facsimile transmission network. Wind maps surveying over1 000 000 km^{2} of ocean can be produced automatically in real time at the radar facility and transmitted directly to forecasters. This capability, which became operational in January 1985, is supported by active research programs directed at improving the scope and accuracy of the measurements, as well as investigating a variety of meteorological and oceanographic phenomena. This paper presents an overview of the JINDALEE remote-sensing program with emphasis on the design and capabilities of the radar system. 相似文献
16.
《Marine Policy》2004,28(1):13-18
Naval strategy and operational focus are shifting toward regional and littoral warfare. The application to extended jurisdictional zones of rules formulated for 3 nm territorial seas is creating international tension as well as new roles for navies. But the argument that the Navy should control the EEZ has fundamental weaknesses. Tentative recommendations are given for reforming the rules of naval warfare in light of extended jurisdictional zones.The growing importance of Rules of Engagement (ROE) reflects a greater degree of control of the military by politicians. This and the spread of high tech weapons have made the operations of naval forces extremely complex. ROE are now being rewritten around three key elements—separation of prohibitions from permissions, determination of the political objective, and conformity between the rules and the force profile and objective. ROE must also be separated from rules of behavior, which are the province of the military. And multilateral naval operations in the same EEZ must have the same ROE. 相似文献
17.
D. E. Calkins 《Ocean Engineering》1999,26(11):1193
The objective of this exercise was the development of a computer simulation of a US Navy towed system (towed body and line array) capable of near real-time predictive capabilities. The purpose of the computer simulation was to be able to determine the lateral motion of the towed body in response to ship maneuvers. The theoretical approach was to develop a spatial-domain computer simulation of each of the towed system components treated as a system, and then develop a “metamodel” of the response by using simple algebraic expressions. At-sea trials were conducted aboard US Navy vessels to verify the simulation and fine-tune its performance. 相似文献
18.
A concern has developed in recent years that extremely low frequency (ELF) electromagnetic fields may be harmful to public health. This concern is evident from opposition to new high voltage transmission lines, opposition to the Department of the Navy's plans to build and operate an ELF Communications System, and anxiety about electromagnetic fields produced in work places and by power distribution lines and house wiring. Measurements made near the Navy's ELF Facility at Clam Lake, WI, and its planned new facility near Republic, MI, presented in this paper, suggest there is a need for substantive date to settle the controversy. 相似文献
19.
20.
Bastiaan J. Collette Kees Rutten Hans Schouten A. Peter Slootweg 《Marine Geophysical Researches》1974,2(2):133-141
Results are given of the Mid Atlantic Ridge section of a transoceanic survey carried out on board of freighters heading for South America and of ships of both the Royal Navy and the Royal Netherlands Navy. The tracks cross the Mid Atlantic Ridge between 12° and 18°N (GEBCO sheets 153/154). 相似文献