This is a negative effect of the calm and stable weather that France has been experiencing in recent days. An episode of air pollution is underway in several regions of the country.
Fine particles accumulate in the air. In addition to PM10, PM2.5 is the most affected. PM 10 are those whose size is less than 10 micrometers, PM2.5 those whose size is less than 2.5 micrometers. As The Weather Channel explains, the most exposed areas are located “around Lyon, in the Seine valley between Paris and Rouen as well as in the Alsace plain”. It is between the capital and the mouth of the Seine that the density of particles is the highest this Monday, according to data from Prev'air, a national air quality forecasting platform.
The cause of this situation is the anticyclone which has settled over France, particularly in the north of the country. By nature, it goes hand in hand with low wind. In addition, it helps to pin particles to the ground. It's a bit the same phenomenon that is happening with the fog which has been struggling to dissipate since last week: the atmospheric pressure exerted by the anticyclone keeps the air mass close to the ground. This lack of air sweeping promotes stagnation of particles. Finally, the heating starts to turn on at this time of year, which is one of the sources of fine particle emissions.
On Tuesday, the situation is expected to deteriorate. Île-de-France would be the most exposed to this pollution. It would also strongly affect the Grand Est, in Alsace and near the borders with Belgium and Luxembourg. Hauts-de-France as well as Normandy near the mouth of the Seine would also be quite polluted.
The forecasts currently predict the persistence of the anticyclone and the absence of wind for the following days. This could make it difficult for pollutants to disperse. If the situation worsens, differentiated traffic could be put in place. In this case, the distinction between vehicles is made on the basis of the Crit'air stickers.
