This paper by Zhou et al. shows the Carbon monoxide (CO), acetylene (C2H2), ethane (C2H6), formaldehyde (H2CO), and hydrogen cyanide (HCN) column retrievals derived from the ground-based FTIR measurements at Xianghe, China. Such new ground-based FTIR datasets, following NDACC protocol with high precision and accuracy, are very important to understand these atmospheric components in this region. Until now, the variations and correlations among these species are not well known in North China, since limited or even no column measurements are available. The measurement and retrieval techniques of the ground-based FTIR dataset are nicely presented and well discussed. The seasonal variations of C2H2, C2H6, H2CO, and HCN are similar to other places (previous studies), while there is almost no seasonal variation of CO at Xianghe, which is different from other places. The paper shows that this weak seasonal variation of the CO column is also observed by co-located TROPOMI satellite and ground-based TCCON measurements. The HCN columns observed at Xianghe are also applied to identify the fire emission in Russia and Kazakhstan. In general, the paper is well-written, and the results are summarized well with novel scientific founds. Therefore, I would like to recommend it to AMT after addressing the following minor comments.

Minor comments:

• P5,Eq1, change the ‘.’ to ‘,’ ‘Where’ to ‘where’

• P10 line 13-14 “The daily mean std of each species within ±1 hour around local noon with at least 2 measurements is calculated to represent the variability of the retrieval. ” I guess I understand what the authors did, but it is confusing from this sentence. Please rewrite it.

• Eq 7, please add an uncertainty component in the formula.

• line 27 – 34. As the uncertainty of the trend is very large due to limited time coverage, and the trend of these species is not the key point of this paper. I would suggest removing this paragraph.

• Please check the reference carefully, as some references are not correctly formatted. For example, P30 line 20. This reference has two times of doi.

Comment on “Understanding the variations and sources of CO, C₂H₂, C₂H₆, H₂CO and HCN columns based on three years of new ground-based FTIR measurements at Xianghe, China” by Minqiang Zhou et al.

General:

This paper describes the variations and sources of CO, C₂H₂, C₂H₆, H₂CO and HCN columns observed with ground-based FTIR at Xianghe in North China along with the retrieval methods. The paper is well described, and it should be published after some minor revisions.

Comments and questions:

1

p3, l7

 Please add the altitude of the Xianghe site.

2.1

p3, l25-28

 If you want to describe only InSb measurements, the number of the optical filter should be 5. I think it is better to describe MCT measurements even you don’t use the spectra in this paper.

2.2

p5, l2

 Please add the version of SFIT4.

l3-4

Full name of NDACC-IRWG was already described in section 1.

l29

What kind of a priori profiles were used for H₂O, HDO, H₂¹⁷O and H₂¹⁸O?

Table 3

Wavenumbers for the retrieval windows of H₂CO and HCN are incorrect.

Figure 3

Don’t you show the observed spectra?

3.1

p11, l10

 10¹⁹ should be 10¹⁸.

Figure 5

 The yellow shaded area is hard to see because it is almost covered by gray dots.

 The box plots become narrow at the median value (Only the box plot for XCO in Figure A1 is box shape).

 As for outliers, did you exclude them in the correlation analysis? I think you used them because they have strong information of the local anthropogenic emissions. So, the word ‘outliers’ is misleading.

p13 l6

42% maybe wrong. 62%?

l27-33

 Is this paragraph worth writing in this paper?

3.2

p14 l16

 less --> smaller?

3.3

p17, l4

 southeast --> southwest?

l17

 south-east --> southwest?

3.4

p18 l3

 trace --> tracer

l5-6

Schroeder et al.(2014) --> (Schroeder et al., 2014)

l9

 Cao et al. (2014) --> (Cao et al., 2014)

p20 l1

 are summed up before each airmass releasing day --> before each airmass releasing day are summed up

3.5

p21 l20

 ‘Emission estimation for C₂H₂ and C₂H₆’ maybe better.

p22

Figure 13

 It is better to put year in figure (b) and (c).

l6-7

 Is this mean that you used the slopes shown in Figure 6? Is it better than using data in categories B and C (or only C)?

p23

 Can you add some more discussion for the difference of the C₂H₂ and C₂H₆ emissions between the inventories and your estimations? The emissions of the two species are nearly the same in two inventories while fossil fuel/biofuels source for C₂H₆ is twice larger than that of C₂H₂ in Table 1. The source values in Table 1 seems to be consistent with your estimations.

4

p23, l20

 10¹⁹ should be 10¹⁸.

l21

 0.92 --> 0.91?

p24 l5-7

 Is this sentence important conclusion? I think it is enough to put this sentence in section 3.1.

l14-15

 ‘come from local anthropogenic emissions’ is explained in the next sentence.

Appendix A

p26 l3

 ‘Since’ should be removed.

Figure A1

 Dashed line is hard to see.