A weather ship was a ship stationed in the ocean as a platform for surface and upper air meteorological observations for use in weather forecasting. They were primarily located in the north Atlantic and north Pacific oceans, reporting via radio. In addition to their weather reporting function, these vessels aided in search and rescue operations, supported transatlantic flights, acted as research platforms for oceanographers, monitored marine pollution, and aided weather forecasting both by weather forecasters and within computerized atmospheric models. Research vessels remain heavily used in oceanography, including physical oceanography and the integration of meteorological and climatological data in Earth system science.
The idea of a stationary weather ship was proposed as early as 1921 by Météo-France to help support shipping and the coming of transatlantic aviation. They were used during World War II but had no means of defense, which led to the loss of several ships and many lives. On the whole, the establishment of weather ships proved to be so useful during World War II for Europe and North America that the International Civil Aviation Organization (ICAO) established a global network of weather ships in 1948, with 13 to be supplied by Canada, the United States, and Europe. This number was eventually negotiated down to nine. The agreement of the use of weather ships by the international community ended in 1985.