This manuscript presents 7 months of observations of aerosol precursor gases at the Finnish sub-Arctic field station SMEAR I. The authors combine their ambient pressure nitrate chemical ionization mass spectrometry measurements of sulfuric acid, methanesulfonic acid, iodic acid and the sum of highly oxygenated molecules with publicly available meteorological and aerosol data from the SMEAR I station. As the authors note, very few measurements of this nature and over such a long timescale are available to gain information on seasonal cycles of aerosol precursors in near-polar regions. For this reason, the present data set is quite interesting and the general analysis provide some interesting insights into aerosol formation chemistry. My main concern is that this analysis is somewhat cursory, and stops short of delving into detailed mechanistic analysis that such a data set can provide. However, I believe that this manuscript is deserving of publication in ACP given that the following mostly minor comments can be addressed.

Minor Comments:

(1) L104-105: what is meant by this statement? perhaps something is missing from the latter part of this sentence?

(2) L143: what is the magnitude of the loss parameter in the 1m stainless steel inlet line?

(3) L146-147 & L159-160: is the -50%/+100% uncertainty quoted only for sulfuric acid? what is the approximate uncertainty for non-sulfuric acid compounds for which the sulfuric acid sensitivity has been applied?

(4) L231: can the authors be more specific about what is meant by 'saturate'?

(5) L290-304: as the authors note in the latter part of this paragraph, does it make sense to speculate about long range transport of HIO3? What is the approximate lifetime of HIO3? Presumably its lifetime is short, and long range transport appears a very unlikely possibility.

(6) L305-313: why focus only on the melting of snowpack? Isn't photochemistry in the snow pack a more likely source? (e.g., Raso 2017, as cited by the authors)

(7) Figure 5: if the relationship between HOM concentration and temperature is most significant here, why not plot temperature on the x-axis and color by radiation?

(8) Figure 7: a diurnal profile of the condensation sink calculated from DMPS measurements would also be informative here, rather than only plotting total aerosol number concentration. (i.e., are the polar marine air masses also cleaner in terms of existing particles before NPF events occur, or does the very large concentration of aerosol precursors overwhelm any differences in condensation sink between event and non-event days?)

(9) Figure 8/10: why do the authors think the O3 is higher when air masses arrive from more northern polar marine regions?

(10) Figures in general: many of the figures have very small axes labels, and are at a resolution that is difficult to read, please enlarge axes labels and legends and improve the figure resolution in the final version.

This measurement report by Jokinen et al. quantifies the seasonal and monthly variation of the important aerosol precursor gases sulfuric acid (SA), methane sulfonic acid (MSA), iodic acid (IA), and highly-oxygenated organic molecules (HOMs) from the remote field station SMEAR I in Värriö Northeastern Finland. The chemical species are measured almost constantly by a state-of-the-art nitrate chemical ionization atmospheric pressure interface time-of-flight mass spectrometer (CI-APi-TOF-MS) in the period between April-October 2019. In addition, the authors link the four chemical species and their seasonal concentrations, as well as meteorological parameters to new-particle formation (NPF) events classified by a Differential Mobility Particle Sizer (DMPS) and a Condensation Particle Counter (CPC).

The overall measurement reported is of good quality and its presentation is well structured, while the language is for the most part precise and fluent. As the authors mentioned, these are the first long-term measurements in a sub-Arctic region that can help the scientific community to understand regional chemical processes and formation of atmospheric aerosol as well as their dynamics in this remote region that is very sensitive to the Earth’s rapid climate change. The scientific methods and assumptions are valid, and the interpretation of the measured data is discussed in detail, while the conclusions are limited and not always entirely clear. The conclusions therefore rather give a rough overview of the detailed mechanism of new-particle formation in sub-Arctic areas. As a measurement report, however, this work provides some interesting insights and serves as the basis for future and expanded research in this region. Since there are no major scientific concerns, I believe that this manuscript can be published in ACP as a measurement report after addressing the following mostly minor comments.

Minor comments:

1. line159-61: Does this LOD of 4x10⁴/cm³ also applies to other species than SA?
2. line197-99: Does these heatwaves have a substantial impact on the NPF at this site? Can the authors elaborate a little more on this in the discussion part as this may more often in the future?
3. Figure 2: Since anthropogenic pollution plumes from the nearby smelters also affect the SMEAR I site, mixing ratios of SO₂ and NO_x should be added here, if available, like it is done in Sipilä et al. (2021). This can help to understand various aspects of the photochemistry at this location (e.g., types of radicals and quantitative estimation, such as OH, NO₃, RO₂) and to separate NPF events from biogenic and anthropogenic sources.
4. line239-41: Why does the missing March data make the comparison (more) uncertain and in what perspective/direction. Can the authors elaborate on how far the diurnal cycle (e.g., peak concentration) or the overall SA concentration might change?
5. line243-53: Is there NO+NO₂ mixing ratios available during this period to state whether the HOMs at SMEAR I are mainly non-nitrate HOMs or organonitrates? This difference can also have a strong impact on HOM dimer formation and thus on NPF at this site. Taking the sum of HOMs (non-nitrate and organonitrates) from Sulo et al. (2021) at SMEAR II would result in a comparable diurnal cycle of total HOMs to SMEAR I. Sulo et al. (2021) shows a clear peak of organonitrates in summer at midday around 1x10⁷ mol./cm³ while the non-nitrate HOMs are at ~ 0.4x10⁷ mol./cm³. In the evening non-nitrate HOMs increase to about 0.8x10⁷ mol./cm³ while the organonitrates begin to decrease but remain almost at the same concentration as the non-nitrated HOMs. It would be easier to follow the discussion and improve the reader's understanding of the various chemical species to include this section on HOMs in the later section starting at line 314.
6. Figure 3: It might be useful to add the diurnal cycle of the global radiation from the different seasons within the plots to link the aerosol precursor gases production to the ongoing photochemistry at SMEAR I station.
7. line314-16: Is the sum of HOM concentration in Yan et al. (2016) similarly calculated to this study (summation between 300-600 Th) and corrected for transmission to be comparable? Please add Yan et al. (2016) to the reference list.
8. Figure 5: I would also recommend plotting HOM concentration on the x-axis and temperature on the y-axis while coloring the global radiation. This might also reveal whether the behavior is linear or else. Does one data point represent a daily mean?
9. Figure 6+7: Since there is a clear seasonal (and even monthly) variation in aerosol precursor gases concentration, I wonder if this also leads to a diurnal variation of NPF events. Therefore, a more distinct seasonal (or monthly) profile of median number size distribution and total particle concentration of the NPF events here would be more meaningful in my opinion.
10. line364-71: The authors may add distinct numbers to the temperature, RH, and global radiation differences between event- and non-event days, as was done for the ozone concentration.
11. line384-87: To what extent are the boundary layer dynamics affected during the day; especially concerning sunrise and sunset during the different seasons. What influence does it have on the measured precursor gas concentrations?
12. line391: Since the concentration of the measured gases depends on the wind direction and the air masses exposed to sources of volatile precursors, it would be great to add the wind direction to Figure 1.
13. line394-401: It looks like the air masses of cluster3 of event days and cluster2 of non-event days passed over the highly polluted region of Kola Peninsula. A representation of the average particle number size distribution as a function of the different air mass clusters could therefore be very helpful here. In addition, as noted by Reviewer 1, the values of the condensation sink and the coagulation sink of small particles are important parameters for the classification of NPF events that should be added to the manuscript.
14. Chapter 3.3: It would be helpful to have an overview showing the aerosol size distribution, wind direction, concentration of small particles or 2-7 nm negative ions, the particle sinks, and the NPF events over the entire measurement period, similar to Figure 2 in the accompanying article by Sipilä et al. (2021). In addition, the NPF events can be highlighted in Figure 1 and Figure 2 using background shading.
15. line409-414: Instead of using the sum of the HOMs, it may be useful to focus only on the ULVOC and ELVOC parts when parameterizing NPF, if possible. As mentioned by the authors, however, HOM may play a minor role in nucleation, while it can strongly influence particle growth and compete for coagulation losses.
16. line415-417: Is there no evidence of mixed clusters between sulfuric acid, iodic acid, MSA, HOM, or possibly bases such as ammonia or amines observed by the nitrate CI-APi-TOF as reported by Sipilä et al. (2021) with the APi-TOF?
17. To maximize the information provided in the abstract, please include unambiguous numbers of aerosol precursor gas concentrations and measured values rather than relative descriptions (e.g., “MSA shows a more distinct seasonal cycle with concentrations peaking in the summer of about 1·10⁸ mol./cm³”; or: “under relatively low temperature (1-8 °C)”). Why is the significant higher global radiation on NPF-event days not mentioned in the abstract?

Technical corrections:

1. Please add the numbering of the individual chapters according to the text.
2. Some passages require language editing.
3. line170: […] were downloaded […]?
4. line247: missing space between ‘are one’.
5. line298: missing ‘t’ in events.
6. line336-337: “[…] and detected aerosol precursor gases during NPF days […].”
7. Figure 6: In the figure caption there is a ‘during’ too much.
8. line369: “The meteorological conditions that favor NPF are thus similar to those at the SMEAR II station in Hyytiälä, […]”.
9. line377: Where does the reference ‘Kulmala et al. (2013)’ belong to? Furthermore, in this line add a ‘C’ to figure reference (e.g., Figure 8C).
10. line467: SMEAR III?
11. The short summary needs to be revised in the second sentence.