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Showing papers by "National Ocean Service published in 1984"


Journal ArticleDOI
01 Jun 1984-Science
TL;DR: Comparison of the observed changes in length of day with variations in the global atmospheric angular momentum indicates that the dominant cause of changes in the earth's spin rate, on time scales from a week to several years, is the exchange of angular momentum between the atmosphere and the mantle.
Abstract: Variations in the earth's rotation (UT1) and length of day have been tracked at the submillisecond level by astronomical radio interferometry and laser ranging to the LAGEOS satellite. Three years of regular measurements reveal complex patterns of variations including UT1 fluctuations as large as 5 milliseconds in a few weeks. Comparison of the observed changes in length of day with variations in the global atmospheric angular momentum indicates that the dominant cause of changes in the earth's spin rate, on time scales from a week to several years, is the exchange of angular momentum between the atmosphere and the mantle. The unusually intense El Nino of 1982-1983 was marked by a strong peak in the length of day.

64 citations


Journal ArticleDOI
TL;DR: In this paper, a non-dynamic algorithm for correcting the geo-centric radius of the SEASAT orbit has been developed, which reduces the satellite altitude error to a few decimeters and requires only weak a priori knowledge of sea surface undulations.
Abstract: A nondynamic algorithm for correcting the geo‐centric radius of the SEASAT orbit has been developed. This scheme reduces the satellite altitude error to a few decimeters and requires only weak a priori knowledge of sea surface undulations. Application has been made to a single three‐day period during which SEASAT took global altimeter measurements of sea surface topography with geographic resolution of 900 km at the equator. The resulting corrected SEASAT ephemeris then enabled computation of a sea surface largely free of the 2 to 7 m error that would otherwise arise from error in the ephemeris distributed with the SEASAT data. Subsequent subtraction of GEM L2 geoid heights from this sea surface has yielded ocean dynamic heights in reasonable qualitative and quantitative agreement with values obtained from oceanographic data. The fact that results of this quality could be obtained from only one three‐day arc of SEASAT data demonstrates the potential of satellite altimetry for determining global o...

38 citations


Proceedings ArticleDOI
27 Sep 1984
TL;DR: In this paper, Monte Carlo simulation techniques have been applied to underwater light propagation to calculate the magnitudes of propagation-induced depth measurement bias errors as well as spatial beam spreading and signal attenuation for airborne laser hydrography.
Abstract: Monte Carlo simulation techniques have been applied to underwater light propagation to calculate the magnitudes of propagation-induced depth measurement bias errors as well as spatial beam spreading and signal attenuation for airborne laser hydrography. The bias errors are caused by the spatial and subsequent temporal dispersion of the laser beam by particulate scattering as it twice traverses the water column. Beam spreading results dictate spatial resolution at the bottom and the receiver field-of-view requirement. Sample temporal response functions are presented. The peak power attenuation relationships developed can be used to predict maxim um penetration depths, Predicted depth measurem ent biases are reported as functions of scanner nadir angle, physical and optical depths, scattering phase function, single-scattering albedo, and receiver field of view for several diverse signal processing and pulse location algorithms. Bias variations as a function of unknown in the field) water optical parameters are seen to be minimized for limited ranges of nadir angles whose values depend on the processing protocol. Bias correctors for use on field data are reported as functions of nadir angle and depth.

30 citations


Book ChapterDOI
TL;DR: Using all available Geos-3 and Seasat altimeter data, mean sea surfaces and geoid gradient maps have been computed for the Bering Sea and the South Pacific as mentioned in this paper.
Abstract: Satellite-borne altimeters have had a profound impact on geodesy, geophysics, and physical oceanography. To first order approximation, profiles of sea surface height are equivalent to the geoid and are highly correlated with seafloor topography for wavelengths less than 1000 km. Using all available Geos-3 and Seasat altimeter data, mean sea surfaces and geoid gradient maps have been computed for the Bering Sea and the South Pacific. When enhanced using hill-shading techniques, these images reveal in graphic detail the surface expression of seamounts, ridges, trenches, and fracture zones. Such maps are invaluable in oceanic regions where bathymetric data are sparse. Superimposed on the static geoid topography is dynamic topography due to ocean circulation. Temporal variability of dynamic height due to oceanic eddies can be determined from time series of repeated altimeter profiles. Maps of sea height variability and eddy kinetic energy derived from Geos-3 and Seasat altimetry in some cases represent improvements over those derived from standard oceanographic observations. Measurement of absolute dynamic height imposes stringent requirements on geoid and orbit accuracies, although existing models and data have been used to derive surprisingly realistic global circulation solutions. Further improvement will only be made when advances are made in geoid modeling and precision orbit determination. In contrast, it appears that use of altimeter data to correct satellite orbits will enable observation of basin-scale sea level variations of the type associated with climatic phenomena.

13 citations


Proceedings ArticleDOI
01 Jan 1984
TL;DR: In this paper, the authors describe the work of the NOAA's Ocean Assessments Division, which has been organizing and synthesizing the best available information on selected characteristics of important regions of the EEZ and conducting comprehensive, "strategic" assessments useful for reducing potential conflicts in the multiple use of resources.
Abstract: The 1983 Presidential proclamation establishing the US Exclusive Economic Zone (EEZ) has prompted new interest in the exploration and development of the resources of this vast oceanic area. Due to the incomplete nature of available information and the resultant uncertain decisionmaking context, decisions that maximize net national benefits from the EEZ will be difficult to identify and make. Since 1979, NOAA's Ocean Assessments Division has been organizing and synthesizing the best available information on selected characteristics of important regions of the EEZ and conducting comprehensive, "strategic" assessments useful for reducing potential conflicts in the multiple use of resources. Recent activities to develop data bases, publish data atlases, develop innovative approaches for identifying and assessing issues, and applying all of these tools to actual and real EEZ-related problems are described.

4 citations


Journal ArticleDOI
TL;DR: In this paper, the benefits of satellite-based radar altimetry for oceanographic research are discussed in connection with the Seasat Altimeter Data Seminar, and a number of criteria are proposed for the successful operation of a satellite based radar altimeter for oceanography applications.
Abstract: The benefits of satellite-based radar altimetry for oceanographic research are discussed in connection with the Seasat Altimeter Data Seminar. After a general review of the oceanographic data collected by the Seasat and GEOS-3 satellites, a number of criteria are proposed for the successful operation of a satellite-based radar altimeter for oceanographic remote sensing applications. It is shown how the interpretation of altimeter return power waveforms can be used to calculate wind speed, ocean circulation and variability in wind, waves, and tides. A number of recommendations for improving the accuracy of radar altimeter data are given which may be incorporated in the design of the GEOSAT and TOPEX research satellites.

4 citations


Proceedings ArticleDOI
D. Friske1, R. Ribe, M. Szabados, D. Dillon, L. Kahn 
01 Jan 1984
TL;DR: In this paper, the authors describe the engineering effort required to implement a prototype wave measurement system for near real-time acquisition and dissemination of wave amplitude data in the Mid Atlantic Bight (MAB) for the NOAA Coastal Waves Program (CWP).
Abstract: This paper describes the engineering effort required to implement a prototype waves measurement system for near real-time acquisition and dissemination of wave amplitude data in the Mid Atlantic Bight (MAB) for the NOAA Coastal Waves Program (CWP). From late 1981 through mid 1983, a variety of methods were employed to extend coastal waves measurements further offshore from the previous CWP line-of-sight buoy system to the edge of the MAB continental shelf. These included a Waverider Satellite (WRS) Buoy, which transmits wave data through GOES satellites and position data through TIROS satellites, and the corresponding deep water mooring system, both of which required extensive developmental testing and modification to meet CWP mission requirements with high reliability and quantifiable accuracy. These efforts are described separately in the following text.