Introduction >> Introduction
The PREV'AIR system was implemented in 2003 upon an initiative by the Ministry for Ecology, Sustainable Development and Spatial Planning (MEDAD) with the aim of generating and publishing daily air quality forecasts and maps resulting from numerical simulations on different spatial scales. The system also supplies observation maps based on measurements carried out on site.
Ozone forecasts are available over the Globe, Europe and France; nitrogen dioxide forecasts, over Europe and France; particles are available on a European scale
The PREV\'AIR system is aimed at all persons and organisations that would like to personally or professionally understand the continent-wide evolution and trends of pollutant behaviour in the short and medium term.
Therefore, under the aegis of the MEDD, the INERIS, the CNRS, the ADEME, and Météo France are developing and implementing the technologies required to compile relevant information on air quality, published everyday on the Internet and filed in a database.
PREV'AIR provides forecasts and maps of ozone, nitrogen oxides and particles, pollutants that are regulated in accordance with their impact on health and the environment. Particle-related information is divided into two categories: PM10, particles with a diameter of less than 10µm, and PM2.5, particles with a diameter of less than 2.5µm.
Maps that represent average concentrations and maximum daily figures of each of these pollutants are drawn up every morning for the same day, the following day and the day after that, on different spatial scales.
A national map is published everyday showing the measurements carried out in France by the Official Air Quality Monitoring Associations (AASQA). This map, updated every hour, enables one to know hourly maximum concentrations, as well as daily mean concentrations observed on the Official Air Quality Monitoring Associations sites. These quantities are computed using the data availble at the current time
Ozone simulations in Europe and France are subsequently readjusted in accordance with observation data available from bodies responsible for air quality monitoring. Therefore, a map is published everyday in the early afternoon, derived from a simulation and corrected with the ozone levels observed in the late morning. This map is then updated once again at the end of the afternoon (usually more often in the event of a pollution incident) in order to include the maximum number of observations and thus improve the reliability of the cartographic representation.
The air quality forecasts and maps published every day are the result of numerical simulations conducted with the help of eulerian chemistry-transport models that allow the calculation of the evolution of photochemical pollution in the lower layer of the atmosphere on different spatial scales (Global, Europe and France).
These are deterministic three-dimensional models: the evolution of pollutant concentrations over time is linked to physical-chemical processes, represented (or "modelled") by mathematical equations resolved numerically at each node of a three-dimensional grid that covers the lower layer of the atmosphere above the area being studied. The spatial resolution varies in accordance with the geographical extension of the area:°
A certain amount of input data, specifically meteorological and pollutant-emission data must be entered into the PREV'AIR system in order to calculate pollutant production or loss flows linked to these physical-chemical processes.
The French Ministry of ecological and solidarity transition (MEDD) coordinates the PREV'AIR project. In addition to its aim of informing the public, anticipating atmospheric pollution events and preparing the affected population, its main objective is to develop national expertise in the field of atmospheric pollution and to actively participate in drawing up effective, relevant control policies.
Technically speaking, PREV'AIR is the result of cooperation between several partners: :
A number of partners contribute to developing the CHIMERE model:
Other bodies provide the input data used within the context of the PREV'AIR system: