Detailed comments are provided in form of a supplementary file, uploaded herewith.

General Comments

The manuscript presents a 17-year regional hydroclimate-chemical reanalysis for Asia (MATCHA) at 12 km spatial resolution using WRF-Chem, including assimilation of MODIS AOD and MOPITT CO and coupling between aerosols, radiation, and snow processes. The development of such a system represents a significant technical effort and the study provides a comprehensive dataset that is likely to be very valuable for the community. In particular, the manuscript includes extensive comparison against independent observations for multiple variables including meteorology, snow cover and atmospheric composition, which is an important strength.

I have a few major comments:

1. It is currently unclear who the primary target users of this dataset are. As mentioned in the abstract, if the dataset is intended to support emission mitigation strategies, additional discussion is needed regarding whether the data quality is sufficient for such use. Clarifying the intended applications and associated limitations of the dataset would greatly improve its application for the broader community.
2. It will be helpful to provide more detailed information on the anthropogenic emission inventories used. Given that the simulation spans approximately 17 years, emissions are likely to have changed substantially across different regions within the domain. These temporal changes could contribute significantly to biases in simulated PM_2.5 and PM₁₀. If possible, it would be useful to compare the emissions used in this study with more recent or alternative inventories to better assess emission-related uncertainties.
3. The manuscript evaluates the dataset against independent observations extensively. However, without some sensitivity analysis, it is difficult to determine to what extent the improvement of model performance is attributed to the assimilation of AOD and MOPITT CO. In addition, one of the key novel aspects of this work is to represent the LAPs and their feedback in the HMA region. The manuscript seems to lack some quantitative analysis to demonstrate the impacts of the BC deposition on snow and the subsequent impacts on snow or hydrology properties. Additional analysis or discussion would strengthen this aspect of the study. 
4. The manuscript includes extensive evaluation across multiple variables and datasets, which is valuable. However, it would be beneficial to provide a high-level summary (e.g., Taylor diagrams or a summary table) that highlights key performance metrics across variables. This would help readers more easily grasp the overall performance and key strengths and limitations of the dataset rather than browsing through each figure or table.

I also have a few minor comments:

1. Line 20: fine particulate matter: PM_2.5 /PM₁₀: this is confusing. 
2. Figure 1 is helpful in summarizing the modeling framework and assimilation workflow; however, the presentation could be significantly improved for clarity and overall quality. The current flowchart is difficult to follow due to cluttered arrows and a lack of clear visual hierarchy among key processes. In addition, the meaning of different arrow colors is not clearly explained. 
3. Regarding sea salt and dust aerosols, it would be helpful to show what PM₁₀ looks like including these two aerosols or a plot to show the contribution of these two aerosols. In addition, for dust aerosols, it would be useful to clarify the relative contributions of local emissions versus lateral boundary transport, as long-range transport may play an important role in this region. Please also specify which dust emission scheme is used in the WRF-Chem model and briefly discuss its potential impact on the results.