The Source Data

The wind and wave observations used to compile this online database were all extracted from the Meteorological Office Main Marine Databank, a collection of reports from ships of the Voluntary Observing Fleet (VOF). The VOF observations are made by the deck officers of merchant ships, and this chapter deals firstly with the nature of the observations themselves and secondly with the Main Marine Databank as a whole.

The Observations

The overwhelming majority of VOF wind and wave observations are visual estimates rather than instrumental readings. Few vessels carry wave measuring equipment, and readings made by ship-board anemometers are affected by the movement of the vessel. This database has been based solely on visually estimated observations to ensure consistency in the basic data. Visual estimates made in a consistent manner are not affected by changes in instrument type, exposure or measuring technique. Guide-lines for making non-instrumental observations of wind and wave parameters are given in the WMO Compendium of Lecture Notes in Marine Meteorology [29] and in [30], and the main points are summarized in Appendix_A1.