Dear Authors: I agree with the Referee that the manuscript has substantially improved and is closer to being ready for publication. In addition to addressing the suggestion by the Referee, please consider my comments below. Thanks.

Page 4 line 10: Please list the range of non-zero concentrations used for the calibration in the text).
Page 4 line 13: Please provide a response time (not just “rapidly”) for the instrument.
Page 4: Was the calibration through the 5 m inlet line and the aerosol filter at the inlet? In other words, was the calibration gas introduced at the beginning of the inlet or closer to the instrument? This would obviously affect response time and have implications for the measurements. Please comment.
Page 4 line 24: Was there any observation of different NH3 losses on a clean versus dirty inlet filter?
Page 5 line 16-17: Please include information on chloride detection limits.
Page 12 line 25: Are the correlations statistically significant? If not, please use a different word.
Page 13 line 3: Please list all the model outputs. Don’t use “etc.”
Page 13 line 3-6: Please also comment on the slope of the regression, not just the correlation. There seems to be a high bias for NH3 and a low bias for sulfate and nitrate (although this may be due to outliers – see comment regarding Fig. 5). Please discuss this and the implications for the results of this manuscript. Please consider including normalized mean error and bias of the measurement-model comparison.
Page 17 line 1: Please consider changing “confirming” to something along the lines of “is consistent with.” Given the qualitative nature of the discussion here, it seems strong to say “confirms.”
Page 17 lines 10-23 & Figure 10: There almost appears to be two distinct regions of data that exhibit different trends– one at low sulfate and one at high sulfate. Can you comment on these two different regimes?
Sect 3.7: Would “transport effects on local ammonia and ammonium” be a better title for this section?

Figures: Please make sure subpanels are labeled in all figures. The resolution on several figures needs to be improved in order to make the axis labels legible.
Figure 4: Please keep the y-axis range the same for all subpanels to make it easier to compare between the subpanels.
Figure 5: In the modeled vs observed sulfate and nitrate there appear to be a few outliers (low modeled, high observed) that are perhaps pulling the fit down. What is the source of these outliers? Are the outlier points for sulfate and nitrate at the same time?
Figure 10: Please include units.
Figure S1: Please improve the resolution of the figure. How long is the signal smoothed for in panel a? Why was the signal smoothed?