|This is a follow-up review to the revision of the Suski et al. manuscript that describes biological aerosol studies of cloud droplet and ice crystal nucleation at the AIDA chamber. In particular, the addition of the CVI cut-size on the cloud particle size distribution plots and the added detailed labeling of the mass spectra are helpful for interpretation of the residual particles. The added section headers in the results and discussion are also helpful. Please see below for remaining comments/questions.|
- SPLAT Particle Size Calibration: While I do not expect this to impact the main findings in this work, in the future, the authors should take care to conduct their size calibration to encompass the entire data range, as the 70-1000 nm PSLs do not cover the full range of particles reported (up to 1.2 um), rather than relying on extrapolation. This also means that the size calibration below 70 nm is very uncertain. Figure 1 shows the small particle detection limit as a green line, but because of the scale on the axis, this cannot be determined. The detection limit should be stated in the methods section (page 6), and the miniSPLAT size distributions shown should start at this value, since the reduced particle number <0.1 um is due to scattering efficiency, rather than a lack of particles present, as shown in Figure 1 through the SMPS measurements. Further, given the reduced transmission at higher diameters, this would make the differences before and during expansion size distributions even greater when this is accounted for; the authors may consider noting this in the manuscript if they haven’t already, as it further supports their results.
- Page 7, Line 16 and elsewhere: Could m/z 30 be NO+?
- Page 2, Lines 20-22: Please provide a reference for this sentence.
- Page 6, Line 8: Fix typo – “um” should be “nm”.
- Page 6, Lines 9-10: The authors state that “The transmission efficiency through the aerodynamic lens is expected to change by only a few percent with the observed pressure changes during the expansion, as shown in Liu et al. (2007).” However, in Figure 2 of the author response, the change in transmission efficiency at >500 nm is nearly 20%, which is much more than “only a few percent”. Please revise this sentence appropriately.
- Page 7, Line 16: Fix typo – 18NH3+ should be 18NH4+. Also, revise sentence so as to not list ammonium as an organic peak.
- Page 7, Lines 25-29: I suggest removing these sentences from the manuscript, as they are not necessary, and in comparing the spectra shown herein with these papers, I think this is subjective to interpretation without a rigorous comparison. Also, it neglects that there have been many other biological SPMS papers that have looked at the intensities of organic ion peaks with laser intensity (e.g. Steele et al., 2003, Analytical Chem.), for example (which would be more appropriate to discuss, if the authors wanted to keep a comment on the organic ion intensities).
- Page 8, Line 27: Fix typo – 18NH3+ should be 18NH4+.
- Figure 3: Since this figure only include m/z labels as numbers, it would be helpful for the Figure 2 labels to include numbers, in addition to the formulas. Also, it would be helpful to add formula labels to the positive ions as you are able to, and use consistent labeling between the positive and negative ion mass spectra. Please also label in the caption if these are average mass spectra. For plots a & c, it would be helpful to show only the scaled (e.g. x10) portion of the mass spectrum for a given m/z range, rather than the original plus this scaled part, as the spectra are currently very busy and showing the peaks twice makes it harder to read.