Proceedings of the Symposium on Global and Environmental Monitoring: Proceedings of the Symposium on Global and Environmental Monitoring

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Persistent identifier:: 856665355

Title:: Proceedings of the Symposium on Global and Environmental Monitoring

Sub title:: techniques and impacts ; September 17 - 21, 1990, Victoria Conference Centre, Victoria, British Columbia, Canada

Year of publication:: 1990

Place of publication:: Victoria, BC

Publisher of the original:: [Verlag nicht ermittelbar]

Identifier (digital):: 856665355

Language:: English

Document type:: Multivolume work

Volume

Persistent identifier:: 856669164

Title:: Proceedings of the Symposium on Global and Environmental Monitoring

Sub title:: techniques and impacts; September 17 - 21, 1990, Victoria Conference Centre, Victoria, British Columbia, Canada

Scope:: XIV, 912 Seiten

Year of publication:: 1990

Place of publication:: Victoria, BC

Publisher of the original:: [Verlag nicht ermittelbar]

Identifier (digital):: 856669164

Illustration:: Illustrationen, Diagramme, Karten

Signature of the source:: ZS 312(28,7,1)

Language:: English

Usage licence:: Attribution 4.0 International (CC BY 4.0)

Editor:: International Society for Photogrammetry and Remote Sensing, Commission of Photographic and Remote Sensing Data

Publisher of the digital copy:: Technische Informationsbibliothek Hannover

Place of publication of the digital copy:: Hannover

Year of publication of the original:: 2016

Document type:: Volume

Collection:: Earth sciences

Chapter

Title:: [TP-3 OCEAN/COASTAL ZONE MONITORING]

Document type:: Multivolume work

Structure type:: Chapter

Chapter

Title:: APPLICATIONS OF GEOSAT ALTIMETER DATA IN THE NORTH-EAST PACIFIC. J. F. R. Gower, and S. Tabata,

Document type:: Multivolume work

Structure type:: Chapter

97 APPLICATIONS OF GEOSAT ALTIMETER DATA IN THE NORTH-EAST PACIFIC J. F. R. Gower, and S. Tabata, Institute of Ocean Sciences, P.O. Box 6000, Sidney, BC, V8L 4B2, Canada Tel: (604) 356-6558, Fax: (604) 356-6479, Telex: 049-7281 ABSTRACT The Geosat altimeter has successfully mapped sea surface height, ice, waves and winds during the 5 years of its life (1984-1989). We present two examples of the use of this data in the north-east Pacific. Consistent sea surface height anomalies with space scales of order 100-300km, are observed at 17 day intervals. Anomaly amplitudes are in the range 10 to 30 cm, with anomaly displacement velocities of about 1 cm/s. These altimetry results are compared with the more precise, but less frequent data from ship hydrographic and CTD measurements. Examples are also shown of wave-height maps derived from Geosat data. The spatial coverage pattern from a single satellite is insufficient to follow the pattern of waveheight growth and decay induced by the global surface wind field, but gives valuable statistical data on the long term average wave climate. 1 GEOSAT ALTIMETER DATA A satellite altimeter measures the travel time of pulses emitted vertically downwards, and reflected back to the satellite by an area of the earth’s surface typically a few kilometers across. Accurate knowledge of the satellite’s position and of the pulses’ propagation speed, allows measurement of the absolute height of the earth’s surface. Over the oceans, the mean flatness of the sea surface on kilometer scales, and the symmetry of height offsets introduced by surface waves, allows a mean range to be determined with a precision of a few centimeters. Such a precision gives important oceanographic data on ocean circulation and on smaller scale motions, since the geostrophic balance of these water movements on a rotating earth requires changes in the mean ocean surface height. These height variations are in the range 10 to 30cm for mesoscale eddies, and up to 100cm at the edges of intense western boundary currents. Horizontal scale of the height changes are of the order of 100km. Oceanic applications of satellite altimeter sea surface height data have been demonstrated by Cheney et al. (1983), Fu and Chelton (1985) and Tai et al. (1989). The US Navy Geosat satellite was designed to provide classified information on the shape of the geoid. This has not been made available to the non-military research community. After completion of these measurements, the satellite orbit was altered to duplicate that of the Seasat mission from which similar data had already been made available in 1978. After November 1986, Geosat was held to within 1km of this nominal orbit and provided a sequence of global altimetry data which has been widely distributed. Some results from this mission were recently reported in a special journal issue introduced by Douglas and Cheney (1990). This is the so-called Exact Repeat Mission (ERM) which began in November 1986, in which Geosat repeated its orbit pattern every 17.05 days. In this period, 244 satellite orbits covered an oblique grid with an equator crossing separation of 164km. This coverage pattern is defined by ascending node longitudes 1.05°E + 360n/244 for n = 1 to 244, orbit inclination of 108.04° and an orbital period of 6037.55s. 2 OBSERVATIONS IN THE N.E. PACIFIC The present study area is shown in Figure 1. Eddies were tracked in the two areas outlined by rectangles. Waveheights were studied in the full area 0 to 60°N, 90 to 180°W. For the eddy tracking use was made of ascending orbits which crossed this area with a mean spacing of about 90km as shown. These correspond to n = 141 to 173 in the formula for ascending node longitudes given above. Similar descending orbits also crossed this area approximately orthogonally to those shown. However, much of the data from descending orbits were unusable due to attitude instability of the satellite after crossing arctic Canada, and information from them is not considered here. Figure 1. Map of the study area showing North America and the Hawaiian islands, the positions of Geosat ascending orbit tracks for n = 141 to 173 and rectangles outlining areas where eddies were tracked, west of California and in the Gulf of Alaska.

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