Satellite observation of long-range transport of wildfires plumes in the northern hemisphere in 2008-2023

Wildfires exert a important influence on the chemical composition of the atmosphere, thereby impacting air quality, ecosystem, and climate forcing. The substantial emission of pollutants from such fires, coupled with their long-range transport, has the potential to counteract the progress achieved in reducing anthropogenic emissions. Numerous studies show that the increase in the frequency and intensity of fires offsets the general trend towards improved air quality observed in regions influenced by wildfires. These studies also caution of an increasing risk of the population being exposed to extreme levels of aerosols and ozone. In addition to their regional impacts, the plumes from the most intense fires can be transported on a continental or even hemispheric scale, thereby imposing health constraints on regions that are not generally affected by widespread, frequent or intense fires.

The northern hemisphere is home to a group of biomes that are particularly sensitive to hydro-meteorological conditions, and therefore to the effects of climate change on burned areas. The majority of the most intense fires of the last two decades have occurred in North America and in the boreal regions of Asia.

This study assesses the impact of fires on the variability of total CO, total PAN and AOD in the Northern Hemisphere using 16 years (2008-2023) of observations from the IASI/MetOp and MODIS/Terra and Aqua satellite instruments. More specifically, the variability in the number of detected plumes of extreme values of CO, PAN and aerosol from fires is studied.

The trajectories of these plumes are estimated using only satellite observations and are used to assess the contribution of the different regions of the Northern Hemisphere to the variability of atmospheric composition. The potential impact of the long-range transport of the identified plumes on air quality is estimated using observations of the altitude of the plumes obtained from both active CALIOP observations and passive IASI observations.

The chemical composition of the identified plumes is characterised using IASI observations of ammonia (NH₃), formic acid (HCOOH), methanol (CH₃OH) and ozone (O₃).