Fig. 1. Overview of the methodology used in this study.

We take two different approaches to speciate INP concentrations using single-particle techniques. The first approach uses the direct measurements of ice crystal residuals with an SPMS to fractionate INP concentrations. The second approach uses single-particle measurements in tandem with size distributions to derive speciated particle surface area distributions. We then apply particle type–specific active site density n_s parameterizations to calculate INP concentrations for different particle types. These two approaches can be used to evaluate the representativeness of dust and SSA INP parameterizations. We take a Lagrangian approach to evaluate model predictive skill. We use a turbulent dispersion model, FLEXPART, to calculate source-receptor influence footprints and combine these source-receptor footprints with particle source functions for dust, SSA, fungal spores, and bacteria along with appropriate n_s parameterizations to predict INP concentrations. The predictive skill of the model is evaluated using the speciated INP measurements. In addition, using high- and low-resolution meteorological data to drive the Lagrangian simulations allows us to assess how model resolution affects our prediction of INP concentrations.