Particulate nitrate plays a critical role in aerosol radiative forcing, and leads to very large uncertainty in climate projection. But very few global climate models have nitrate included, and only sparse studies evaluated the nitrate simulation performance. This work provides a comprehensive evaluation of the nitrate simulation in six global climate models again in-situ observations over north American, Australia, Japan and south Asia, Europe and Africa. This work not only evaluate the simulation of nitrate mass concentration at the surface level, but also for the vertical profile and gas-aerosol partitioning of nitrate. I think this work fits well with the scope of ACP. Although the scientific value is appreciated for this work, I would like to make a few suggestion hopeful could help improve the presentation of this article for publishing in ACP.

1) IPCC AR5 2013 is referred. I recommend refer to the latest IPCC AR6 2021, to keep the research up to date.

2) Line 75-77. This sentence is not clear. Please rephrase it.

3) Thanks for providing comprehensive review of previous studies in nitrate simulation, in the Introduction section. However, the presentation, or the writing style, would need some improvement. Rather than just listing what has been done previously (e.g., L80-90, and many other), but also better to summarize a key message you would like to express to audience.

4) “MOSAIC explicit treats the heterogeneous reactions on HNO3 on dust and sea salt particles …”. What about particles of other species? Are reactions treated independently for each size mode, or a bulk treatment for particles spanning all modes?

5) Line-150. Why? Or you may want citation here to support your argument.

6) last line of page-6. Change to “with 1 year spin-up and the last 10-year results for analysis”.

7) Line 184.  Should be Table-2?

8) In the discussion, where possible, better to briefly engage some discussion about ammonia, sulfate, sea-salt and dust simulations. Since, this could help point towards clearer directions for improving nitrate simulation. Excessive ammonia after neutralizes sulfuric acid can then contribute to particulate nitrate.

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