Formation of small airborne particles from condensable gases is a ubiquitous process in the atmosphere. These secondary particles make a substantial contribution to total ambient aerosol numbers, and have effects on cloud formation and climate as well as human health. The precursor gases, including acids, bases and organic species, originate from both human and natural emissions such as traffic, industry, agriculture, vegetation and sea. Reducing uncertainties related to the formation mechanisms is a central question for assessments of aerosol sources and effects.
Building model representations is, however, challenging: On one hand, detailed models are needed for understanding the complex physical and chemical processes that determine the numbers of formed particles in different environments. On the other hand, complicated and detailed schemes are not feasible for large-scale climate and air quality models, which instead require simplified but robust approaches.
These needs are addressed by two projects at the SMHI Meteorology research unit:
- AeroFrame: Explicit framework from molecular clusters to nanoparticles for resolving atmospheric aerosol formation dynamics, and
- AeroSources: New generation tools for robust quantification of atmospheric nanoparticle sources.
The projects aim to build reliable and easily applicable model tools, with the following main goals:
- To create a novel framework for explicitly resolving the formation dynamics, from the initial agglomeration of gas molecules to the growth of the newly-formed particles by vapor uptake. Such approach is needed for quantitative assessments of nanoparticle concentrations.
- To construct and evaluate approaches for simplified application of particle formation rates in atmospheric models. This enables straight-forward incorporation of molecular model predictions in large-scale models.
- To make the tools openly available to the atmospheric modeling community.
At present, the central model frameworks have been released and implemented in, for instance, air mass trajectory and global climate models. Results demonstrate promising approaches for simplified treatment of common formation mechanisms through e.g. sulfuric acid and ammonia. Pathways involving lower-level trace gases such as amine species, however, are likely to involve more uncertainties when treated in a very simplified manner.
About the projects
The projects are active 2020–2023, and are funded by the Swedish Research Council Vetenskapsrådet, and the Swedish Research Council for Sustainable Development Formas.
Project manager: Tinja Olenius, SMHI Research for Meteorology – Environment and Climate