Review of “The Arctic Low-Level Mixed-Phase Haze Regime and Its Microphysical Differences to Mixed-Phase Clouds”

This manuscript presents an observational study of Arctic low-level mixed-phase haze (MPH), distinguishing it from Arctic mixed-phase clouds (MPC). Overall, the manuscript is well-structured, with thorough scientific analysis and clear visualizations through figures and charts. I recommend publication after the authors address the following comments.

Major Comments

1. Clustering and Physical Interpretation
   
   The authors employ clustering and statistical analysis to interpret the underlying mechanisms of the observed phenomena. However, observational data alone do not directly confirm physical processes (e.g., during HALO-(AC)³, the synoptic situation primarily controls the ABL top temperature, while surface-driven processes determine its vertical extent). The logical connections could be strengthened by incorporating back-trajectory analyses—especially in Section 2.3, and at Lines 183 and 207 in Section 3.1.1.
   
   
   
   
2. Clustering Justification and Consistency
   
   In Table 1, MPH is divided into sub-clusters 2a and 2b, which are later recombined for microphysical comparisons with MPC. The rationale for creating sub-clusters (e.g., 2a vs. 2b, or 1a vs. 1c) is unclear. Line 136 mentions that Table 1 lists the thresholds defining each regime, but the basis for these choices isn't fully explained. Additionally, there's no figure provided to support Lines 288–289. It appears that in many sections, sub-clusters are merged (e.g., 2a+2b → 2), raising the question of whether the initial subdivision is necessary. While Lines 200–221 are logically structured, please clarify the importance of including these sub-clusters in the context of the central narrative. Why are these regime details crucial for the main scientific conclusions?
   
   
   
   
3. Suggestions for Figure 2
   
   Figure 2 shows large variability, and the gray lines do not provide as much value as intended. I suggest replotting the three profile types in separate panels with a shared axis range, using the color scheme from Figure 3. Each panel can include all dropsondes of that type along with an averaged profile. This restructuring would facilitate cross-comparison with Figure 3, support the discussion on “exceptions and normals” (p. 8), and better illustrate inversion frequency.
   
   
   
   
4. Further Analysis of Figure 4 by Environment Type
   
   Figure 4 is already informative, but the analysis could be enhanced by breaking it down by environment—such as marginal ice zone (MIZ), open ocean, and sea ice. Including additional subplots by surface type would provide valuable insights for readers and future studies.
   
   
   
   
5. Clarity in Figure 5
   
   Figure 5 is the most difficult to interpret due to the complexity of the color-coded “step” histograms. Would it be possible to separate Ice and MPH into an additional column or panel to reduce visual clutter?
   
   
   
   
6. Clarify Novelty and Contribution in Introduction
   
   Please clearly state the novelty of this study in the Introduction, ideally around Line 50. For example: "In this study, we conduct a detailed investigation of a previously unclassified cloud regime, which we refer to as the mixed-phase haze (MPH)." Is this the first study to define MPH as a unique regime? Does the novelty stem from high-resolution in-situ observations? How does this work advance beyond previous research? These elements are hinted at throughout the Introduction, but an explicit statement would help readers better understand the contribution.
   
   
   
   
7. Line 340–341: Secondary Ice Production?
   
   The statement that NINP is lower than the haze droplet number (Line 340) might also suggest the influence of secondary ice production. If so, the "Therefore" at Line 341 feels misleading. Please clarify the logical flow here.
   
   
   
   

Minor Comments

• Line 6: "The particle number concentration" — specify what kind of particles (e.g., hydrometeors?).
  
  
  
  
• Line 17–24: Consider shortening this part of the Introduction. The discussion begins focusing on clouds at Line 25, so the earlier text may be unnecessarily long.
  
  
  
  
• Line 49: Add citation for the Wegener–Bergeron–Findeisen (WBF) process.
  
  
  
  
• Line 63: "Three research aircrafts" → should be "three research aircraft".
  
  
  
  
• Abstract: Consider combining the two paragraphs into one for better flow.
  
  
  
  
• Lines 90–100: The description of instruments could benefit from a summary chart. This could include size ranges, acronyms, uncertainties, transmission efficiency, and lower/upper limits.
  
  
  
  
• Indentation inconsistencies: e.g., Lines 280–281. Please ensure consistent formatting throughout the manuscript.

Summary:

This is a scientifically rich and well-organized study. The observational analysis is impressive, and the topic—especially the distinction of the MPH regime—is of great interest. Addressing the issues above, particularly those related to clustering logic, figure clarity, and novelty statement, will significantly improve the manuscript and make it more accessible to a broader scientific audience.