This manuscript reports high–time/mass resolution online molecular measurements of OA using EESI-TOF at a mountain site in SE China, comparing cloud droplets, interstitial, and cloud-free aerosol. It is clearly within ACP’s scope, addressing atmospheric composition and processes with implications for aerosol–cloud interactions and climate. However, the discussion of “tracers” requires more caution: the manuscript should clearly distinguish between true tracers and compounds showing enhanced signals, define the concept explicitly as illustrated below.

Major comments:

1. Introduction: the current motivation for a cloud‐droplet study is underdeveloped. The Introduction should more clearly articulate (i) why in-cloud processing matters for OA burdens and properties, (ii) what key uncertainties remain despite prior fog/cloud and online/offline molecular studies, and (iii) why an online, molecular-level approach (EESI-TOF) is uniquely positioned to address those gaps. Please sharpen the problem statement, specify the hypotheses, and state the concrete research questions and expected contributions of this dataset.
2. Line 246-249 and AqSOA tracers about siloxanes. The current discussion and explanation is not accurate. In particular, the concepts of “tracers” and “enhanced compounds” should be clearly distinguished. Please clarify the likely sources and implications of the siloxanes, or restructure this section accordingly. In fact, siloxanes are commonly used in personal care products and industrial chemical products.The lifetimes of the siloxanes are relatively long and will undergo atmospheric oxidation process to generate SOA, as confirmed in both laboratory and ambient studies [1, 2]. But in the aerosol phase, the high-molecular-weight siloxanes have also been detected from vehicle and jet emissions [3, 4]. The siloxanes could also be attributed to the use of silicone tubing in the sampling line [5]. Could the authors confirm that the silicone tubing was not used in the sampling system? It would also be helpful to show the time series of these compounds over the entire campaign. Was there an AMS or PTR-MS available to provide supporting information? Were any siloxane SOA tracers detected (e.g., Si- containing compounds where one or more methyl groups are replaced by hydroxyl groups)? In summary, the discussion could be better connected the focus of this study, as the siloxanes are good surfactants and could influence cloud droplet activation.
3. Section 3.3, considering the AqSOA tracers: the mass resolution and capbility of EESI-TOF are not enough to identify the structure of compounds, especially the N-containing species. Many of the proposed tracers could also arise from other sources (e.g., biomass burning, anthropogenic emissions, or in-spray artifacts) rather than exclusively as the tracer of AqSOA. For example, C9H18N2 and C12H23N are more deteched by EESI-ToF from traffic, microplastic, and agriculture, rather than the AqSOA. So it’s hard to treat proposed tracers as candidates unless supported by high-resolution MS/MS, authentic standards, or orthogonal constraints (e.g., gas-phase precursors, isotopic patterns). Again, the concept of the tracers cannot be used in this kind of discussion.
4. The manuscript relies heavily on earlier and in-campaign citations (71 % before 2020) and does not sufficiently reflect recent literature (29% from the most recent 5 years, e.g. Line 48-57, line 219-222, line 246-294). In particular, line 269 lists tracer studies from 2017 and 2019, but more up-to-date work is available from 2019-2025. Note that EESI-TOF was developed around 2017, first field measurements appeared in 2018–2019 (Switzerland), and the first report of aqSOA measured by EESI was published in 2021. The manuscript should be revised to incorporate these and subsequent studies, ensuring comprehensive and current coverage beyond the authors’ own campaigns.

Minor comments:

Line 61: “Aerosol Mass Spectrometer (AMS) or Aerodyne Aerosol Chemical Speciation Monitor (ACSM)”.

Line 82: revise to “…at the summit of Damaojian Mountain, located in Jinhua City, Zhejiang Province, China.”

Line 105: delete “Here is a brief introduction.”, too informal.

Line 115: “signal-to-background ration (s/b)”.

Line 268: “To the best of our knowledge, this is the first observation of C16H48O8Si8 …”. As mentioned in major comments 2, the description needs to be considered.

Line 308: hours to a day.

1. Chen, Y., et al., Chemical characterization and formation of secondary organosiloxane aerosol (SOSiA) from OH oxidation of decamethylcyclopentasiloxane. Environmental Science: Atmospheres, 2023. 3(4): p. 662-671.
2. Meepage, J.N., et al., Advances in the Separation and Detection of Secondary Organic Aerosol Produced by Decamethylcyclopentasiloxane (D5) in Laboratory-Generated and Ambient Aerosol. ACS ES&T Air, 2024. 1(5): p. 365-375.
3. Yao, P., et al., Methylsiloxanes from Vehicle Emissions Detected in Aerosol Particles. Environmental Science & Technology, 2023. 57(38): p. 14269-14279.
4. Decker, Z.C.J., et al., Emission and Formation of Aircraft Engine Oil Ultrafine Particles. ACS ES&T Air, 2024. 1(12): p. 1662-1672.
5. Timko, M.T., et al., Composition and Sources of the Organic Particle Emissions from Aircraft Engines. Aerosol Science and Technology, 2014. 48(1): p. 61-73.

The study characterized the molecular composition of the organic fraction of cloud droplet residue, pre-cloud aerosols, interstitial aerosols, and post-cloud aerosols using EESI-ToF-MS. The approach yielded a high-resolution dataset that captured detailed temporal variations in molecular composition. While the study provided additional evidence on the relative contributions of CHO and CHON species in cloud droplet residues and aerosols, its findings largely corroborated previous results rather than extending current understanding. The authors interpreted their data mostly relying on findings from previous studies.

The study’s main points were: 1. 39 new compounds in cloud droplet residues; and 2. the hypothesis that accretion reactions were promoted during cloud processing. However, it remains unclear why these new 39 compounds were detected. Were they revealed because of the dataset’s high temporal resolution, the unique analytical technique, or chemistry specific to the sampled environment?

The study period experienced four cloud events, effectively providing four data points for comparing pre-cloud, CD, INT and CF samples. Caution should be exercised in drawing general conclusions from such a limited dataset. For instance, CE2 was an exception in which CHON did not comprise the largest fraction of total OA, and CHO was not the lowest among the four sample types. Thus, one quarter of the samples did not align with the generalization, and it would be advisable to moderate some of the claims derived from these comparisons.

Specific comments:

1. Line 27: “With adjacent time” is not clear. Adjacent to what?
2. Line 44-46: Research on the role of aqueous-phase chemistry in SOAs has been going on for more than four decades. Are the studies cited here seminal ones?
3. Line 51-52: What are the main findings from Duan et al. (2021)?
4. Lines 151-153: Are the ranges for C, H, O, and N – C:10.01–12.81 vs 8.43–11.10, H: 14.59–20.34 vs. 14.23–16.83, O: 5.08–6.00 vs. 5.06–5.72, and N: 0.34–0.43 vs. 0.16–0.35 – between CD and pre-loud really that different?
5. Line 278: “Large fluctuations” in what?