Extreme Aerosol Loadings from Iberian Peninsula Wildfires

Large wildfire episodes can substantially perturb regional aerosol loads and atmospheric composition; however, their quantitative impact remains difficult to constrain due to uncertainties in fire emissions, plume rise, and aerosol properties. During August 2025, exceptionally intense wildfire events affected large areas of the Iberian Peninsula, leading to severe aerosol emissions, reduced visibility, and pronounced air-quality degradation over extensive regions. In this study, we investigate these events by ground-based aerosol observations from CAECENET, an automatic system that retrieves vertically-resolved and column-integrated aerosol properties by applying the GRASP (Generalized Retrieval of Atmosphere and Surface Properties) inversion algorithm to combined sun–sky photometer and ceilometer measurements (Román et al. 2018).

The atmospheric aerosol emissions are primarily characterized at several sites in Spain and Portugal, including Valladolid, Madrid, Badajoz, Évora, and Granada. This network provides continuous measurements of optical and microphysical aerosol properties, enabling detailed monitoring of aerosol optical depth (AOD), fine and coarse mode contributions, and temporal evolution during the episodes. In addition, information on aerosol vertical distribution and plume heights is analyzed to assess the altitude at which fire related aerosols were injected and transported.

Satellite based fire products from the Global Fire Assimilation System (GFAS) and surface European Monitoring and Evaluation Programme (EMEP) data are used to complement this analysis.

This study highlights the value of dense ground-based aerosol networks such as CAECENET for monitoring extreme wildfire impacts, providing essential information to complement satellite observations and models, and for the assessment of the radiative effects of fire-emitted aerosols.

This work was supported by the Ministerio de Ciencia e Innovación (MICINN), with the grant no. PID2024-157697OB-I00. This work is part of the project TED2021-131211B-I00375 funded by MCIN/AEI/10.13039/501100011033 and European Union, “NextGenerationEU”/PRTR, is based on work from COST Action CA21119 HARMONIA and the Marie Sklodowska-Curie Staff Exchange Actions with the project GRASP-SYNERGY (grant no. 10 101131631). Financial support of the Department of Education, Junta de Castilla y León, and FEDER Funds is gratefully acknowledged (Reference: CLU-2023-1-05). This work was funded by European Comision through the EUBURN-RISK project (INTERREG-SUDOE; S2/2.4/F0327). The authors acknowledge the support of the Spanish Ministry for Science and Innovation to ACTRIS ERIC.

Román, R. et al., 2018: Retrieval of aerosol profiles combining sunphotometer and ceilometer measurements in GRASP code, Atmospheric Research, 204, 161-177.