The Impact of aerosol&ndash;ice nuclei-cloud interactions on a Typical Spring Dust-Precipitation Event in China

Zhang, Jian; Zhou, Chunhong; Shen, Xiaoyu; Wang, Hong; Zhang, Xiaoye

doi:https://doi.org/10.5194/egusphere-2025-4127

Preprints

https://doi.org/10.5194/egusphere-2025-4127

Preprints

09 Sep 2025

| 09 Sep 2025

The Impact of aerosol–ice nuclei-cloud interactions on a Typical Spring Dust-Precipitation Event in China

Jian Zhang, Chunhong Zhou, Xiaoyu Shen, Hong Wang, and Xiaoye Zhang

Abstract. To investigate the impact of ice nuclei (IN) activated by dust aerosols on precipitation over China, this study uses regional Global/Regional Assimilation and Prediction System – China Meteorological Administration Unified Atmospheric Chemistry Environment (GRAPES/CUACE). The original temperature-dependent IN nucleation scheme is improved by incorporating an on-line aerosol–IN nucleation scheme. The INs are fed on-line into the Double-Moment 6-Class (WDM6) cloud microphysics scheme in a typical dust affected precipitation event in East Asia.

The on-line aerosol–IN nucleation scheme modifies the spatial distribution and density of IN. Compared with the systematic underestimation in original WDM6, INs reach 10³–10⁴ L⁻¹ with the improved scheme, and cloud ice is reasonably formed between 2 and 6 km in height.

The scheme alters the distribution of cloud hydrometeors, making it closer to observations. Above the freezing level, the ice-phase hydrometeors mixing ratio decreases due to the higher cloud-top temperatures in dusty weather. And the ratio of cloud ice to cloud snow changes from 1:1 to 1:3. Near the freezing level, increased cloud ice converts to cloud water, resulting in its increasing. During the dust-precipitation event, rainwater is decreased due to vapor competition between IN and cloud condensation nuclei.

The scheme also modulates the precipitation distribution closer to observations. It suppresses precipitation near dust source areas, where accumulated precipitation decreased by about 1.5 mm, while the downstream precipitation increased by about 0.18 mm.

Received: 23 Aug 2025 – Discussion started: 09 Sep 2025

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Jian Zhang, Chunhong Zhou, Xiaoyu Shen, Hong Wang, and Xiaoye Zhang

Status: final response (author comments only)

RC1:
'Comment on egusphere-2025-4127', Anonymous Referee #1, 09 Oct 2025
This study investigated the IN effects on precipitation over China using GRAPES/CUACE model with improved IN nucleation scheme. The topic is interesting and the authors provided detailed analysis on how dust particles affect the cloud microphysics and precipitation pattern. However, some parts of the manuscript is difficult to understand, and I have some questions about this research, which are listed as follows.
General comments
The logic contradiction. The discussions related to Figures 3 and 4 mentioned the reduction of mass concentration of ice crystal compared between T_CCNIN and T_CCN (or between T_CCN and T_CTL), while the IN nucleation rate is increased in T_CCNIN run. Why does enhanced IN nucleation lead to reduced mass concentration of ice crystal? However, in some part of the text, the authors stated “more ice-phase cloud particles” (L442-444) and “cloud ice increases” (L345-347). The descriptions about the IN effects on ice microphysics are inconsistent in the manuscript, which makes me confused about the conclusions.

The heterogeneous ice nucleation scheme. The authors mentioned at L201-202 that the parameterization of Jiang et al. (2016) was derived from dust events in Xinjiang, Huangshan, and Nanjing, China. But in the Introduction part, the authors cited from the same literature (Jiang et al., 2016) and wrote that the dust events were only observed in Huangshan and Nanjing. Please check the correct location of the dust events in the literature (Jiang et al., 2016). And are these dust events cover all 3 places during their lifetime? Moreover, if the authors are interested in the effects of dust particles on precipitation, why not chose an ice nucleation parametrization that developed base on the dust events occurred only over Xinjiang, which is much closer to the dust source area? As I know, Huangshan and Nanjing are not the major source of the dust events. The atmospheric condition of Huangshan is relatively clean and the main aerosol source of Nanjing could be the polluted aerosols. Even the dust event may pass through these places, the dust particles may be mixed with the local emitted aerosols (lie polluted ones) and make the ice nucleation being complicated.

The horizontal resolution of 0.15º is too coarse for investigation of IN effects on precipitation from aspect of microphysics. And the output interval of 3 h is too long to analyze the IN nucleation and related microphysical processes.

The English gramma of the manuscript should be improved.

Specific comments:
Section 2: The authors mentioned that “The aerosol size spectra have been divided into 12 size bins” (L148-149), and they also noticed that WDM6 scheme is a double moment (bulk) 6-class microphysics. I would like to know how a size-resolved aerosol scheme being coupled with a bulk microphysics?

Section 2.3: How are the advection of IN (that are not nucleated into ice crystals yet) with winds considered in the T_CCNIN test?

L23-24: I don’t understand how the on-line aerosol-IN nucleation scheme modifies the density of IN.

L24-25: What is the definition of the number concentration of IN? Is that the number of dust particles with diameter exceeding a threshold (like 0.5 μm)? Or is that the number of dust particles that can be activated into ice crystals under appropriate temperature and saturation conditions based on equations 2 and 3? And from which figure did the authors reach the conclusion that “INs reach 10³-10⁴ L⁻¹ with the improved scheme”? I did not find the related discussions about the magnitude of IN number.

L29-30: “the ratio of cloud ice to cloud snow”: Is that “the ratio of mass concentration of ice crystal to that of snow”?

L30-31: It is difficult to understand this sentence.

L31-33: Please explain why “rainwater is decreased due to vapor competition between IN and cloud condensation nuclei”.

L60-62: Are there dust events in Huangshan and Nanjing, China?

L69-73: Please explain why the relationship between precipitation events and dust storm frequency shows a significant negative correlation at interannual scales but a positive correlation at monthly scales.

L74-76: Please explain why “dust aerosols tend to suppress precipitation over arid and semi-arid areas in spring, while promoting it in summer”.

L67-84: I did not find a clear logic in this paragraph. Please improve it.

L112-114: I don’t understand what this sentence is used for.

L151-152: The horizontal resolution is 0.15º for the simulation in the present study. It is too coarse to investigate the IN effects on cloud and precipitation from the aspect of microphysics. Can the authors conduct the additional runs with fine resolution to see if the results are robust?

L167-169: I don’t understand this sentence. In the original WDM6 scheme, is only the nucleation of ice from vapor considered (like condensation freezing and deposition nucleation)? How about the other ice nucleation schemes, like immersion freezing, contact freezing, and homogeneous freezing?

L169-172: Did the nucleation of IN consume water vapor in the original WDM6 scheme? I didn’t find the effect of water vapor on the ice nucleation from equation (1).

L178-180: This sentence is difficult to understand.

L192-193: There is no “Δ𝑡” in equation (2).

L194-195: Why do the deposition nucleation and condensation freezing only occur at temperature between 248.15 K and 258.15 K. This temperature range seems too narrow.

L198-200: Please provide the evidence for this sentence.

L207: What are the physical meaning for “ρ” and “q_I₀”?

L212: Does “ρ_i” mean the density of ice? Why take the value of 500 kg/m³?

Equation (5): Please provide the reference for equation (5).

L252-255: It is difficult to understand this sentence.

L264-265: The output interval of 3 h is too long to investigate the microphysical effects of IN. The cloud system might change evidently during this time period.

L272: As I know, there are three types of horizontal resolution of NCEP FNL data, i.e., 2.5°, 1°, and 0.25°. Please provide the link for the NCEP FNL data with resolution f 0.15°.

L293: The equation of aMAPE has been introduced in equation (8).

L293-294: It is difficult to understand this sentence.

L299: What is the vertical resolution of the simulations? I mean how many levels are included between 3 km and 5 km?

Figures 2a-c: Please introduce how to calculate the IN number. Is it the number of dust particles with diameter exceeding 0.5 µm?

Figure 2d: I don’t understand the label of x-axis. Is it the IN nucleation rate? If so, the unit of nucleation rate should be #/kg/s (number of newly nucleated ice crystal per second) or g/kg/s (mass of newly nucleated ice crystal per second). Furthermore, the authors are encouraged to compare the nucleation rate of different types of regimes, such as deposition nucleation, condensation freezing, immersion freezing, and homogeneous freezing.

Figures 2c-d: The figure title mentioned the results are from T_CCN and T_CCNIN, but the legends in both panels show T_CTL and T_CCNIN.

I didn’t find discussion or explanation about Figure 2 but only introduction of the figures at L298-305.

Figures 3 and 4: What does “event averaged hydrometeors” mean in the figure title? And it should be “averaged mass concentration of different types of hydrometeors” instead of “averaged hydrometeor”.

Figure 4: What does Qv stand for? Is that water vapor mixing ratio? The water vapor is not a kind of hydrometeors, and the Qv profiles were not referred in the main text.

L328-330: What is the basis for the authors to divide this case into 3 phases?

L337-339: What is the reason for higher temperature in T_CCNIN case than the other 2 cases? Moreover, how does the temperature change of 0.1-0.5 ℃ lead to so remarkable reduction of ice crystal mixing ratio? The authors are suggested to explain this question in more detail. And if the warmer environment is the reason for the reduced mass of ice crystal, the IN nucleation rate should be decreased, rather than increased at 4-6 km compared between T_CCNIN and T_CTL as shown in Figure 2d. Moreover, why did IN nucleation occur below 4 km with temperature above 0 ℃? It does not make sense.

L344: I can not find in Figure 4 at which level the mass concentration of ice crystal is reduced up to 0.1 g/kg. The maximum value of Qi is smaller than 0.05 g/kg as shown in Figure 3.

L345-347: Here the authors mentioned that “cloud ice increases” but in the last sentence they just wrote “cloud ice mixing ratio decreases by…”. I am very confused about the inconsistency of the expressions.

L356-359: I don’t understand what does cloud ice “transforms into cloud water” mean? Is it melting of cloud ice into liquid water? if so, the height for the increment of cloud water should be below 0 ℃ layer for melting occurs. But the difference in Qc peaks above 0 ℃ layer for phase 1 (Figure 4a, d). Please clarify it.

L362-363: Please provide enough evident for competing available water vapor between INs and CCNs, such as comparing the diffusion growth rate of cloud droplet and ice crystal.

Figures 3 and 4 show the vertical profile of mixing ratio of graupel. But it seems not referred in the main text.

Figure 6: It seems that the improvement of CCN or IN nucleation contributes insignificantly to the changes in precipitation pattern. The inherent defects of the numerical model (e.g., microphysics, dynamics, or the initial and boundary conditions) may play more important role in the evolution of cloud field and spatial distribution of precipitation.

L403-404: From which figure the authors found “the suppressed cloud water is transported downstream in T_CCNIN”?

L419-422: The authors are suggested to explain this results in more detail.

L436: I can’t find from which figure the authors reached the conclusion that “IN concentrations reached 10³-10⁴ 𝐿^-1 between 3 and 5 km altitude”. Figure 2c shows the maximum number concentration is between 10²and 10³ 𝐿^-1.

L430-438: I did not find the discussion related to the number concentration of IN in Section 3 Results.

L440-441: Please explain why “dust suppresses the formation of ice-phase hydrometeors”?

L442-444: I can’t understand this sentence. First, why does “higher cloud-top temperature” and “more small-sized ice-phase cloud particles”? The warm environment should suppress the IN nucleation. Second, why “both of which could limit ice-phase hydrometeor development”? Does “ice-phase hydrometeor” include “ice-phase cloud particles”? It makes me confused.

L453-456: Please explain how “increasing production rate for nucleation of ice suppress the precipitation”. Moreover, what is the relationship between suppressed precipitation and reduced cloud and rain water? Please state it in more detail.
Citation: https://doi.org/10.5194/egusphere-2025-4127-RC1
RC2: 'Comment on egusphere-2025-4127', Anonymous Referee #2, 16 Oct 2025

please see the attached file for the comments.

Citation: https://doi.org/10.5194/egusphere-2025-4127-RC2
CC1:
'Comment on egusphere-2025-4127', Honglei Wang, 17 Oct 2025
Dust aerosols are a significant global source of ice nuclei. This study implements a double-moment cloud ice scheme and incorporates an on-line aerosol–IN nucleation scheme to explicitly represent heterogeneous processes. The topic is very interesting, and the obtained results can enhance our understanding of the mechanisms through which dust influences ice nuclei. This topic is suitable for publication in ACP. However, before publication, the following issues need to be improved.
While the study focuses on the mechanisms of dust's impact on ice nuclei, the abstract provides limited discussion on this aspect. Relevant conclusions should be supplemented.

The manuscript contains several formatting issues that require careful revision. For example, the font in "2.2 WDM6 microphysics scheme" is noticeably inconsistent.

In Section 3, the analysis should focus more on phenomena and mechanisms. Descriptions of figures and tables, such as those in lines 298-304, can be directly included in the captions.

The discussion in "4 Conclusions and discussion" should be integrated into Section 3.

In lines 430-440, the improved on-line model simulates significantly higher ice crystal concentrations compared to the WDM6 results. What causes this? This is a key highlight of the study, yet the authors did not provide an in-depth or systematic explanation in Section 3. The authors should systematically analyze the mechanisms behind the improved simulation performance after the model enhancement.

Finally, this study focuses on the impact of dust processes on ice nuclei and precipitation, utilizing model simulations. However, the analysis in Sections 3 and 4 provides limited discussion on the influence of the dust event, which is only described in "2.4 Case description and test design." The analysis of model results should incorporate the evolution of the dust process, rather than merely analyzing the simulated ice crystal and precipitation outcomes. In summary, this is a highly meaningful study, and the authors are encouraged to strengthen the analysis of the model results.
Citation: https://doi.org/10.5194/egusphere-2025-4127-CC1

Jian Zhang, Chunhong Zhou, Xiaoyu Shen, Hong Wang, and Xiaoye Zhang

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Short summary

To quantitatively investigate the influence of ice nuclei (IN) activated by dust aerosols on cloud and precipitation during a typical dust-affected precipitation event in China, this study enhances the GRAPES/CUACE model by incorporating an online-aerosol–IN nucleation scheme, which can not only modify the spatial distribution and density of IN and distribution of hydrometeors, but also ultimately improve precipitation simulation by 15 % through modulating the distribution of precipitation.


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