Study of biomass burning pollution over the Amazon using modelling and satellite data

Significant ozone levels are observed every year in the Amazon during the burning season, with potential risks for populations and ecosystems. The dynamics that govern the distribution of biomass burning pollution across the region and hence, the impact on surface ozone are still unknown. Fire activity is predicted to increase, due to its strong dependence on global warming and droughts. Thus, understanding the vertical distribution of biomass burning emissions in the Amazon is crucial to determine and quantify the impacts. For that, this work uses satellite observations, aircraft and ground-based measurements and ozonesondes, combined with an Earth system model. The first part of this work characterises the vertical distribution of Amazonian smoke plumes from satellite observations and analyses major factors of variability. The statistical analysis of smoke plume characteristics combined with an extensive dataset on the main drivers in smoke plume dynamics revealed that most smoke concentrates below 2.5 km and plume heights depend largely on biome type, fire properties, and atmospheric and drought conditions. Specifically, droughts enhance fire activity, favour lower smoke plume heights and larger emissions, which may result in poor regional air quality, with important implications in the future, when more severe and extended droughts are expected. To improve the vertical distribution of biomass burning pollution across the Amazon in Earth system models, an injection height scheme derived using observations of smoke plumes in the Amazon is applied. The simulation shows better performance at representing ozone compared to observations, particularly close to the fires. Furthermore, results evidence a significant impact of biomass burning emissions on ozone levels, and a considerable decline in air quality across populated and vegetated areas. These outcomes highlight the necessity of including improved representation of the vertical distribution of biomass burning emissions in future air quality studies and provide insights of the magnitude of biomass burning impact on air quality, enhancing scientific understanding of the significance of biomass burning in the Amazon.