摘要:

Altimeter residuals from a global spherical‐harmonic adjustment of satellite altimetry can be used as observations in a subsequent, or second‐phase, adjustment of a short‐wavelength oceanic geoid in terms of point‐mass magnitudes as parameters. An important part of the development presented is the formulation of the second‐phase adjustment via a banded or a banded‐bordered system of normal equations. This task encompasses three separate features: (1) elimination of the point masses from an observation equation if they are sufficiently far from the pertinent observation point, (2) special arrangement of the point‐mass parameters in the adjustment scheme, and (3) resolution of the resulting system through an adaptation of the well‐known Choleski algorithm. If only the point‐mass magnitudes are subject to adjustment, one is concerned with a banded system of normal equations. If selected tidal parameters are also implicated, this system becomes banded‐bordered. In fact, the former is a special case of the latter in every respect. By virtue of this approach (with or without tidal parameters), geoid undulations over large ocean basins can be adjusted in a few overlapping strips of point masses, leading to a detailed resolution of the entire oceanic geoid.

ISSN:0149-0419    

DOI:10.1080/01490418609388016

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The approach presented is directed toward a specific adaptation of the least‐squares collocation with noise, yielding smooth predictions of geophysical quantities. The smoothing corresponds here to a truncated gravity field equivalent to an(n’, n')spherical‐harmonic expansion. This is reflected in the truncation, at the degree n‘,of the pertinent covariance and cross‐covariance functions in most (but not all) instances. The smooth predictions of geophysical quantities, made in an equilateral grid corresponding to the truncation degree n‘,serve in constructing contour maps after having been densified for the needs of a contour routine. Such a densification is carried out efficiently via errorless collocation with the degree truncation n‘ throughout. Consistent with this procedure, “residuals” at observation points (i.e., discrepancies between the contour map and the data) are computed using the same algorithm. The complete collocation approach is utilized for a 2° resolution of the earth's gravity field with emphasis on the oceanic geoid, based on the residuals from a global spherical‐harmonic adjustment of SEASAT altimetry. The presented results include contour maps of geoid undulations and gravity anomalies. They are compared to the results of a point‐mass adjustment, another technique based on the spherical‐harmonic adjustment. The agreement between these two techniques is found to be excellent.

ISSN:0149-0419    

DOI:10.1080/01490418609388017

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The Northwest Atlantic Regional Energetics Experiment (REX) will study the dynamics and energetics of the Gulf Stream and associated rings. Bottom‐moored inverted echo sounders with pressure gauges (IES/PGs) will collect in situ data which both complement and augment the GEOSAT altimeter measurements in the Northwest Atlantic. The primary objective of these data will be the intercomparison of satellite and IES/PG measured fluctuations in sea surface topography and mean ther‐mocline depth. However, more detailed and absolute intercom‐parisons of these data would be available if the IES/PG could be positioned in an inertial reference frame while the measurements were taken. This paper presents an error model for computing the accuracy of positioning with a bottom beacon of the IES/PG type. Equations for studying the use of acoustic range data for locating an IES/PG with respect to a ship's track are developed and presented. The ship's track is assumed to be located in inertial space to the 1‐ to 2‐m level by application of the GPS (Mohan, 1983, 1984). Effects of depth‐dependent acoustic speed are included. Although IES/PGs as presently deployed would have to be modified to function as the type of ranging device described in this paper, the representative parameter values that have been calculated for the Northwest Atlantic REX show that sub‐1‐meter accuracy in location determination can be expected. A crucial factor is the measurement pattern, and recommendations for optimal patterns are presented.

ISSN:0149-0419    

DOI:10.1080/01490418609388018

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The exceedance probability of tsunami occurrence in the eastern Pacific was estimated as an extended Poisson process. Estimation was also undertaken for several blocks in the eastern Pacific. Some tsunamis that originated off South America hit the Japanese islands after crossing the Pacific.

ISSN:0149-0419    

DOI:10.1080/01490418609388019

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Panel on Ocean Bottom Positioning, National Research Council,Seafloor Referenced Positioning: Needs and Opportunities(Washington, D.C.: National Academy Press, 1983).

ISSN:0149-0419    

DOI:10.1080/01490418609388020

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

ISSN:0149-0419    

DOI:10.1080/01490418609388015

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor