The authors present the INP measurements from two sites. They find that INP concentrations at the mountaintop site are on average lower than high valley site. The authors discuss the importance of the orographic effect towards the INP concentrations. This is a unique study where the authors have analyzed the field INP data in the context of meteorology. I have the following minor comments, and after addressing these comments I recommend publication.

Line 13: Sentence needs to be revised. Maybe add Our results “show that” the local ….

Section 2.1: It is not clear why a heated inlet was used. Would this affect the composition of ambient aerosol? Do volatile components of these aerosol will be evaporated? On Line 110, can a special feature of the inlet design (that prevents snow sampling can be explained here? What is the cut size of this inlet?

Section 3.4: Equation 4, how height, h, is calculated?

Section 3.5: Did the vertical profiles of potential temperature were measured? In Figure 6 (line 262), it is mentioned: “the potential vertical mixing” – please elaborate. It is not clear whether vertical mixing occurred or not. If yes, how this is justified. It is not clear what test was used to confirm the vertical mixing.

Conclusions: To enhance the impact, how INP concentrations observed in this study compare with other field studies? Line 416, is this “absence of a relation” view supported by other studies? Can APS (Figure 2e) data be shown here? On line 418, it is said that this relation does not hold for a temperature warmer than -20 degC. Is this temperature threshold based on the present study? Are experiments are performed at colder temperatures to conclude this statement?

This is a careful detailed study of INP from two sites separated vertically over complex terrain.  The vertical transport of INP is investigated.    Overall, I suggest publication with the following minor revisions.  

Abstract Line 3:  I would state this phrase more carefully.   “INP, which measurements suggest are sparsely populated in the troposphere.

Introduction Line 15:  Field and Heymsfield, 2015 is not an appropriate or original reference for this statement.

Starting at Line 38.  It is important to clarify earlier that an idealized PBL is in a well-mixed state with constant potential temperature and aerosol number concentration with height.  This is stated later an idealized description, but should instead be clarified initially.

Line 56 – I am confused by term “arbitrary”

Line 115 – more information is needed pertaining to the inlet.  What is the efficiency of the inlet at different aerosol sizes? 

Line 190 – clarify why locations were omitted, since trajectories passed close to mountain tops?  The reasoning here is unclear.

Figure 3 – excellent plot, easy to understand

Line 237 – this can also be caused by a combination of both (down from higher altitude and local sources)

Line 244 – what 3 scenarios are referenced here?  soot, biomass burning (with and without dilution), or…   This may need to be rephrased.

Figure 5, can you speak to the uncertainty of the measurement (or at least statistics around the medians).

Line 254 – Important point is that global long-range transport events were removed.  This should be stated at other times within the paper.

Figure 6 – can you add the % of cases (or number of cases) for each of the 4 wind scenarios?

Figure 7 – the use of “/” rather than (StdL^1) is quite confusing.  It appears as a ratio rather than a unit.

Figure 8 – are all 4 panels needed.  There is very little science results outside of the NW plot.  Could the other 3 panels be moved to supplemental figures?

Figure 9:  I found this confusing.  The color bar states that orange references 24-48 hours before sampling. Yet the caption states that orange circles indicate locations where a trajectory’s ten minute time step was lower than 500 m above ground.  Why are these two conditions met at the same time?

Line 370-385 – This is speculative and potentially should be phrased with less certainty.