QUALITY CONTROL OF GEOSAT WAVE DATA FOR ENGINEERING APPLICATIONS

M. Siddabathula, Vijay G. Panchang

Abstract


Engineers are often confronted by a paucity of useful wave data needed for a variety of applications. Available information is presently derived from three sources: wave buoy measurements, wave model calculations, and ship observations. Of these, buoy measurements constitute the only reliable data source. However, they provide exceedingly sparse spatial resolution. (For instance, there are only about 45 wave buoys in operation in US waters (Franklin 1992)). Wave modeling (with models such as WAM and the Army Corps' Wave Information Studies) provide a data base of uniform spatial and temporal resolution, but despite many advances, wave modeling must still be considered an evolving field and model results are not fully reliable. Visual ship observations have been used to construct global wave climatologies (e.g. the US Navy Marine Climatic Atlas of the world). However, ship-reported wave observations are irregular and usually regarded as highly imprecise. This difficulty with traditional data sets may be overcome to some extent by using the large amounts of data collected in recent years by satellites (GEOS-3, SEASAT, Geosat etc.). The US Navy satellite GEOSAT has recorded ocean wave data for almost 5 years. Circling the globe about 15 times a day, GEOSAT gave the densest coverage compared with all existing data. After the initial 18 months of its mission (31 March 1985 to 30 September 1986), it was maneuvered into an exact repeat mission (ERM; November 1986 to January 1990), when the satellite executed 17-day repeat cycles. Global oceanographic information for some 30 oceanographic parameters were recorded every second. These data have been processed by the National Ocean Service (Cheney et al. 1991a, b) and are disseminated to the user community on CD-ROM's. The data are in the form of "Geophysical Data Records" (or GDR's) for the ERM period and "Crossover Difference Records" (or XDR's) for the initial 18 month period. Significant wave heights (SWH) measured by an onboard altimeter were calculated as an average of 10 values recorded every second. About 50,000 measurements, made every 6.4 km along track, were reported daily.

Keywords


GEOSAT; wave data; quality control

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