New pollution peak in Paris and in several regions, the map of the areas concerned

2019-02-26T06: 37: 00.000Z – Guillaume Woznica

The anticyclone, its benefits and its misdeeds … If the sun and softness delight the holidaymakers of February, these high pressures also have a much less pleasant consequence with a deterioration of the air quality due to a high concentration in fine particles. A new peak of pollution is even expected in the next few hours. Paris region but also in the Hauts-de-France, valleys and alpine Auvergne, along the axis Rhone and around the Bordeaux agglomeration.

Improvement at the end of the week

With a weak wind, the air quality will be mediocre again this Tuesday in Paris and Île-de-France with an index of 6/10. Same observation in Auvergne and Aquitaine while the index will reach 7/10 in the Lille metropolis, in the alpine valleys and in Normandy. The Atmo index will deteriorate again Wednesday with a wind becoming this time zero. Just like last week, the information threshold should be exceeded in the Paris region from the north to the east of the country.

An improvement is expected from Thursday with the gradual withdrawal of the anticyclone that will give way to a more threatening sky in the west. A disturbance will bring some rain and wind to these areas, which will dispel the cloud of particles and significantly improve the air quality. At the same time, mistral and tramontane will rise in the Mediterranean. The eastern regions will have to wait until Friday to see the rain come and finally breathe better.

In Paris, the authorized speed will be reduced by 20km / h for the day of Tuesday on all the fast roads to avoid the production of too much fine particles. In the Nord, Pas-de-Calais and the Auvergne-Rhône-Alpes region, speed reduction measures have also been taken by the prefectures.

Blame it on the anticyclone

Typical situation of winter, when a high pressure is positioned on the west of Europe as is currently the case, the quality of the air is deteriorating. Involved, the inversions of temperatures created by the presence of these high pressures. With a generous sunshine during the day, the sweetness is needed in the afternoon and in the absence of the same cloud cover at night, the temperatures become cool with sometimes frost at sunrise. Thus, the ground cools faster during the night than air at altitude which stays warmer and which will play a role of cover by trapping particles near the ground.

In addition, these pollutants, mainly from road traffic and wood heating, can not disperse because of the absence of wind under the anticyclone. Thus, the fine particles accumulate with concentrations that become more and more important. The lowering of the maximum speed on motorways and highways of Ile-de-France in recent days has nevertheless reduced the concentration of particles but the strengthening of the anticyclone between Tuesday and Wednesday is fearing a new spike in pollution.