Assessing the Chemical Evolution of Biomass Burning Plumes through Airborne Campaigns and Satellite Observations

Wildfires and biomass burning are increasingly frequent and intense worldwide, including in Europe. Recent fire seasons, such as 2017, 2022, and 2025, have severely affected southern Europe, degrading air quality and altering atmospheric composition far beyond the fire regions. Driven by drought, higher temperatures, and climate change, these events release large amounts of trace gases (CH₄, CO, CO₂, NOₓ, VOCs) and fine particles, forming chemically complex plumes that act as reactive atmospheric systems. These plumes strongly influence oxidant levels, secondary aerosol formation, and regional air quality. However, major uncertainties remain in understanding how ozone and secondary aerosols form and evolve as plumes age and disperse. Identifying the key controlling factors, such as vegetation type and moisture, combustion intensity and phase, injection height, and interactions with other anthropogenic or natural sources, is essential to improve understanding of these processes.

Targeted measurements of reactive trace gases (NOₓ, NOᵧ, CO, CO₂, CH₄) and aerosols are required. Diagnostic ratios, including the Modified Combustion Efficiency (MCE), O₃/CO, NOᵧ/CO, and Ox/NOz (O₃ + NO₂ vs. NOᵧ – NOₓ), provide valuable insights into combustion characteristics, chemical reactivity, and ozone production efficiency (OPE) within plumes. These parameters can be obtained from airborne campaigns, which offer high-resolution information on plume structure and composition.

Field campaigns, however, are limited in time and geographic coverage. Satellite observations are thus critical to extend measurements over larger spatial and temporal scales. Yet, satellite retrievals face challenges: spectral interferences and atmospheric variability, such as water vapor, clouds, dense smoke, or aerosols, can distort the signatures of key gases. Aerosol-rich plumes are particularly challenging because absorption and scattering by particles can bias satellite gas retrievals, such as those from IASI. Comparisons between in situ and satellite observations are therefore essential to assess the consistency of observations and provide a basis for future corrections. Accurate aerosol characterization is crucial, as aerosols affect both gas detection and chemical processes within plumes. Coordinated measurements from airborne campaigns and satellite missions, such as EarthCARE and MTG/FCI, will allow comprehensive assessment of aerosol properties and their role in plume chemistry and transport.

This thesis is part of the EUBURN program, led by CNRM (Météo-France/INSU, PI: C. Denjean; https://euburn.aeris-data.fr/), which addresses these gaps through coordinated ground-based and airborne measurement campaigns across Western Europe. Gathering over 30 research institutes, meteorological centers, and public agencies, EUBURN aims to document and model biomass–fire–atmosphere interactions from local to regional scales. EUBURN consists of a series of summer field campaigns, beginning with the EUBURN-SILEX aircraft campaign in southern France in 2025, followed by drone and balloon campaigns in Andalusia, Spain, in 2026, and the large-scale EUBURN-RISK campaign in Portugal, Spain, and France in 2027. These intensive campaigns will deploy aircraft, drones, helicopters, balloons, mobile laboratories, and fixed ground sites as part of a three-year enhanced observation period (2025–2027).

Within this context, the thesis will focus on several key tasks:

1. In situ measurements analysis: Process and interpret airborne and ground-based observations of trace gases and aerosols to characterize plume composition and evolution.
2. Tracer ratios and chemical diagnostics: Compute MCE, O₃/CO, NOᵧ/CO, and Ox/NOz to assess combustion efficiency, ozone formation potential, and chemical reactivity within plumes.
3. Comparative analysis with satellite data: Compare in situ observations with satellite measurements (IASI-NG, EarthCARE, MTG/FCI) to evaluate consistency, investigate spectral interferences, and provide a basis for future data corrections.
4. Investigation of aerosol–gas interactions: Examine the role of aerosols in detection biases and chemical processes within plumes, integrating in situ and satellite observations.
5. Synthesis and modeling support: Integrate results to provide insights into chemical evolution of biomass burning plumes, supporting improved atmospheric modeling and fire impact assessment.

This integrated approach, combining field data analysis, satellite comparison, and chemical diagnostics, will provide a comprehensive understanding of biomass burning plume chemistry and observational challenges, forming the core of the thesis.

e LPC2E a pour tutelles principales le CNRS, l’Université d’Orléans et le CNES. Il comporte trois équipes scientifiques dont les travaux portent sur : (1) la physico-chimie de l’atmosphère terrestre, motivée par les problématiques du changement global lié aux émissions continentales (feux, zones humides….), à la qualité de l’air et à l’évolution de la couche d’ozone, et la physico-chimie des lunes, comètes et astéroïdes du système solaire ; (2) les relations Soleil-Terre et la physique des plasmas spatiaux, pour comprendre les interactions entre le rayonnement et les particules provenant du Soleil, et les environnements ionisés de la Terre, des planètes, des lunes et des comètes ; (3) l’astrophysique, avec l’étude multi-longueurs d’onde des pulsars et des exoplanètes, ainsi que les contraintes sur la physique fondamentale.
Le laboratoire s’appuie sur la forte compétence en instrumentation de l’équipe technique (spectrométries de masse et infrarouge lasers, compteurs d’aérosols, capteurs électriques et magnétiques…), comprenant la conception, la réalisation, la mise en œuvre et l’exploitation des données d’instruments au sol ou embarqués à bord d’avions, de ballons et de satellites. Ces compétences sont reconnues internationalement comme en témoigne la participation du laboratoire à de nombreux projets des agences spatiales et environnementales.

The candidate should hold a Master’s degree in atmospheric sciences, environmental sciences, chemistry, or a related field. Strong skills in atmospheric chemistry, air quality, and data analysis are highly desirable. Experience with field campaigns, airborne measurements, remote sensing, or satellite data interpretation would be an advantage. The candidate should also have a solid background in programming (Python, R, or MATLAB) and data visualization, as well as the ability to work independently and collaboratively in interdisciplinary teams.