French operational capacity in oil spill drift forecast is based on Météo-France and Cedre expertises. Drift forecasts rely on a pollutant drift model, named MOTHY. The system includes local area hydrodynamic coastal ocean modelling and real time atmospheric forcing from meteorological models. MOTHY has been operational since 1994 and has been extensively used during Erika (December 1999) and Prestige (November 2002) crises in the Bay of Biscay. It is used for real cases about 600 times a year.

Cedre and Météo-France roles

French response capabilities in case of accidental water pollution are based on Cedre's expertise in mitigation of both oil and chemical spills in marine and inland waters. As a non-profit association under the Ministry of the Environment, Cedre acts for national organisations (such as the French Navy or Civil Security) or for private companies (oil and chemical industries, and shipping companies). Cedre is also a member of the E.U. Task Force team, to assist European Union and foreign governments in response to accidental pollution.

Météo-France (the French national weather service) has national and international responsibilities to agencies fighting marine oil pollution. Météo-France can intervene at a national level within the spill response plan POLMAR-MER in case of a threat for the French coastline, and at an international level within the Marine Pollution Emergency Response Support System (MPERSS) for the high seas. In order to answer to these commitments, Météo-France developed the pollutant drift model MOTHY.

It is to ensure an optimal reliability that Cedre and Météo-France set up a technical collaboration formalised by a convention signed in 1996. Météo-France send weather forecasts and pollutant drift forecasts to Cedre. In return, by its experiments and interventions on real pollution, Cedre contributes to the improvement and the validation of the model.

Marine Pollution Emergency response Support System (MPERSS)

The National Weather Services have the vocation to bring in real time meteo-oceanic information to various users, among whom organisations in charge of the control of pollution. They traditionally provide data and services to assist the operations in territorial waters. These services work then in close connection with the authorities in charge of the fight at sea. With an aim of ensuring a comparable service in quality in international waters, the WMO set up since 1994 the Marine Pollution Emergency Response Support System for the high seas (MPERSS). It initially aims at setting up a coordinated system intended to provide weather and oceanographic information - when it is necessary and on request - for emergency interventions in the event of marine pollution out of territorial waters. The oceans and the seas are divided into areas of responsibility called MPI areas (Marine Pollution Incident), they correspond to METAERAS areas of the Global Maritime Distress and Safety System (GMDSS) On each of these zones, the weather assistance is coordinated by an Area Meteorological and Oceanographic Co-ordinator (AMOC) which is a national weather service.

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Key features of the MOTHY model

The MOTHY model developed by Météo-France is used on an operational basis to predict the drift of pollutants on the ocean surface. It is based on a limited domain ocean model coupled to a pollutant dispersion model forced by wind and pressure fields provided by an atmosphere model. The oil slick is modeled as a distribution of independent droplets that move in response to currents, turbulence and buoyancy.

A model development validated on real cases

The model was calibrated on well documented pollution incidents such as Torrey Canyon (1967), Amoco Cadiz (1978), Tanio (1980), Gulf War(1991), Aegean Sea (1992) and on sea trials.

Operated since 1994

Operated since 1994 in the marine forecast section at Météo-France, it has been used extensively for the Erika and Prestige incidents. A meteorologist on duty is able to run the model on request. About 500 interventions each year are conducted in real time.

Floating objects drift predictions

Drifting objects at sea are a real danger to navigation. The maritime authorities thus wish to be able to announce their position to the navigators, or to recover them. These last years, the model has been extensively used for search and rescue operations.

Sea trials

In order to answer as well as possible when the accident occurs, Cedre and Météo-France permanently seek to the improvement of their response capacity to a crisis. Regularly, they take part jointly in exercises which allow them to test this capacity and to evaluate the performances of the system.