Improve microphysical models using in-situ data

Current aerosol microphysics models — the models that simulate how injected particles form, grow, and interact — contain significant uncertainties because they were developed with limited observational constraints. They were largely tuned to match observations following volcanic eruptions rather than systematically validated against real-world stratospheric measurements. NOAA's SABRE program (Stratospheric Aerosol processes, Budget and Radiative Effects) flies a state-of-the-art instrument suite and has collected comprehensive aerosol measurements at altitudes relevant for SAI since 2022. This suite provides the most comprehensive set of existing observations of stratospheric aerosol properties, including aerosol size distributions, composition, and optical characteristics.

By using these observations to systematically test and adjust aerosol microphysics models, researchers can identify which physical and chemical processes existing models represent accurately and which require refinement. This process will also reveal which specific measurements are most critical for predicting aerosol behavior in SAI scenarios, thereby informing the design of future observational campaigns. Understanding how to effectively use real observational data to improve existing models is essential before developing detailed design of the observational strategy for an aerosol microphysics experiment.

This activity updates an aerosol microphysics model to match the SABRE observational dataset, using inverse methods to optimize the model fit. The work uses a sectional microphysics modeling framework (such as TOMAS or similar) coupled with a stratospheric chemistry scheme to simulate aerosol evolution and composition. The inverse analysis will systematically adjust key model parameters and process representations — including nucleation rates and mechanisms (both neutral and ion-mediated), condensation coefficients, and coagulation kernels — to minimize differences between model predictions and SABRE observations of aerosol size distributions, composition, and optical properties.

The activity will also determine which of these parameters the available SABRE data can meaningfully constrain and which remain under-constrained. By testing the sensitivity of model outputs to variations in different processes and comparing results to observations, the activity will identify which measurements from the full SABRE instrument suite provide the most critical constraints on aerosol microphysics. This analysis will reveal redundancies in the observational data (measurements that provide little additional information) as well as critical gaps in current observations. The updated, observationally grounded microphysics model and the identified essential measurements will provide the foundation for designing an optimal observational strategy for future field experiments and for predicting SAI-relevant aerosol processes.