Impact of Landes forest fires on air quality in France during the summer 2022

Abstract. The atypical huge forest fires observed in France during the summer of 2022 are modelled using the CHIMERE model. Scenario simulations are performed without and with these fires to quantify the impact of these extra emissions on air quality thresholds exceedances. Additional processes are added in the model to better simulate fire emissions and then have more realistic simulations. The fires influence the characteristics of the surface by destroying the vegetation and creating new erodible surfaces. This increases the mineral dust emissions, but also reduces the Leaf Area Index, then decreases the biogenic emissions and the dry deposition of gases such as ozone. Results show that the fires induce numerous increases in surface ozone and Particulate Matter concentrations close to the sources but also in downwind remote sites such as the Paris area. During the period of the most intense fires in July, the impact of concentrations is mainly due to emissions themselves, when later, in August, ozone and PM concentrations continue to increase but this time due to changes in the burnt surfaces.