1. Applying the N12 desert-dust parameterization to aged anthropogenic/pyrogenic crystalline Fe-containing particles is a major assumption. The paper itself notes that aging effects are complex and laboratory data are lacking. How do you justify using N12 for combustion-derived aluminosilicate glass, magnetite, and coated fly ash? What is the uncertainty if ice-active site density differs by even an order of magnitude?
2. Source contributions are computed as differences between nonlinear INP parameterizations (Exp1 – ExpX). This can yield negative contributions or sums >100%. How many negative values occurred? How were they handled in the ternary diagrams (Fig. 5), which require non-negative fractions summing to 100%? Were the fractions normalized, and if so, how does that affect the reported anthropogenic/pyrogenic/lithogenic apportionment?
3. Marine bioaerosol at −30°C is contradictory. The text says marine INPs at −30°C are “out of the parameterization range and thus are not presented,” yet Fig. 6a includes a marine contribution and Fig. 3e shows marine INPs at −30°C. Are these zero, extrapolated, or from a different experiment (e.g., W15)? Please clarify.
4. The spherical surface-area assumption and the 80% reduction in gravitational settling velocity are not adequately justified. Combustion-derived Fe-bearing particles are often irregular, agglomerated, and coated, so spherical surface area may bias N12-derived INP concentrations. What observational constraint supports an 80% settling reduction, and how sensitive are the source attribution and winter North Pacific conclusions to these choices?
