Instrumental Data

Measurements of waves have been recorded for many different purposes by many different agencies using many different types of instrument, and the resulting data have been analysed and archived in many different ways. Thus, although instrumental data are considered to be generally the most reliable, their availability and quality are subject to wide variations.

Some areas, especially continental shelf regions in which there has been a high level of ocean engineering activity, are reasonably well endowed with instrumental data of good quality (though availability is often limited by restrictions of commercial confidentiality). Some wave and wind data providing global coverage, derived by remote sensing from satellites [10] are also available, but so far the period of years spanned is relatively short.

It is only possible here to offer a brief summary of the current position regarding availability of instrumental data and for this purpose it will be convenient to consider records derived from satellites separately from those derived from surface based or 'in situ' instruments.

Regarding 'in situ' data, a key role is played by the Marine Information and Advisory Service of the UK Institute of Oceanographic Sciences (IOS/MIAS) as a source of data, information and associated advisory Services. IOS/MIAS has been formally designated (by the Intergovernmental Oceanographic Commission) as 'Responsible National Oceanographic Data Centre (RNODC) - Waves' and has global responsibility for information and services relating to instrumental wave data. In this capacity it has compiled a 'Catalogue of Wave Data' [11] providing periodically updated information about the availability of 'in situ' instrumental data worldwide.

Regarding data from satellites, so far two missions have yielded data, spanning more than a year and providing global coverage, which are commercially available. The first is the GEOS-3 (Geodynamics Ocean Satellite) mission which yielded data spanning the period April 1975 to November 1978, available in a global atlas [12]. The second is the so called 'Exact Repeat Mission (ERM)' of the GEOSAT (Geodetic Satellite) which was launched in November 1986, and at the time of writing is still feeding global carpets of wave height and wind speed data into an archive held by the US National Environmental Data Satellite Information Service of the National Oceanic and Atmospheric Administration (NESDIS/NOAA). An account of the mission and the Scope and quality of the data may be found in [13].

NOTE: The above text was written in 1986, to accompany the book 'Global Wave Statistics' [1]. Since that date substantially more satellite data has been collected. There has also been much further development of hindcast models, both global and for specific locations. These now form reliable alternate sources of data, which should be taken into account in critical design decisions.

The duration of these other data sources, however, still fall well short of the 130 years of visual observations processed by the NMIMET analysis process to produce the Global Wave Statistics database. The results from this database are therefore much less influenced by short term climatic variation.

Also Global Wave Statistics Online provides quick and convenient access to the data, making it ideally suited to an initial review of the expected climate for a location or vessel route.