Biomass burning aerosols in the southern Amazon basin: impacts on the water vapor flux and net ecosystem exchange of CO2 based on EMAC/JULESnumeric systems

This study aims to understand how tree photosynthesis and transpiration rates are modified under overcast sky conditions, including densely smoke-laden skies resulting from forest fires and cloud-covered environments. We hypothesize that forest transpiration is being significantly altered in areas affected by BBOA (biomass-burning organic aerosols) due to changes in closely linked biophysical drivers that regulate both transpiration and photosynthesis. This issue is particularly relevant in critical regions where organic aerosol emissions are frequently higher or where cloud cover may have increased in recent years, with implications for rainfall recycling processes in the Amazon Basin that remain insufficiently documented, thereby posing challenges for current numerical modeling frameworks. Using long-term measurements from the FLUXNET dataset across Central Amazonia, Africa, Asia, Malaysia, Indonesia, and northern Australia, we aim to demonstrate the annual water loss induced by aerosols and clouds over tropical forest regions. To this end, we examine key exogenous factors that influence plant photosynthetic activity under different sky conditions. Evapotranspiration (ET) and water-use efficiency (WUE) are analyzed not only as functions of aerosol optical depth (AOD) and cloud cover, but also in relation to the solar zenith angle (SZA), leaf canopy temperature (LCT;), vapor pressure deficit (VPD), and the fraction of diffuse PAR radiation (fPARD). The scientific outcomes will provide a basis for projecting future scenarios using existing global models. To clarify the milestones underlying the objectives above, the following project goals are planned for the next three years: Project Goals - Goal I (Year 1): Analysis of data generated by carbon and energy flux tower systems, remote sensing, and modeling, including the development of computational routines for a comprehensive database. Pilot tests (sensitivity, adaptation, and methodological tuning) will be conducted. Analyses may be carried out at the CCAD (Advanced Computing Center / UFPA) or at the supercomputing facility of DKRZ in Hamburg, Germany. Goal II (Year 2): Preparation of numerical experiments, including data acquisition, analysis, and certification of modeled outputs. Model adjustments may be required, potentially increasing computational time, as the project is strongly linked to numerical experimentation. Goal III (Year 3): Generation of final results, scientific writing, publication of peer-reviewed articles in journals relevant to the project’s thematic scope, dissemination of results (website), workshops, and outreach activities, including media coverage.