|This is the second round of review of the manuscript entitled “The impacts of marine-emitted halogens on OH radicals in East Asia during summer” by Shidong Fan and Ying Li. It is my opinion that the revised manuscript has addressed most of the major issues identified in the original manuscript, and the quality, especially the clarity, of the manuscript is greatly improved. Especially, the major drivers of iodine-induced OH production are clearly identified via Figures 3, 4, and 7, and Figure 8 made some of the key inputs transparent. The authors also carried out additional sensitivity tests (in addition to the nicely designed suite of experiments) to evaluate the impact of anthropogenic emissions on halogen chemistry. I appreciate the efforts the authors have invested in addressing my previous comments. I would recommend this manuscript for publication after very minor (mostly technical) suggestions and clarifications.|
Line 47 (revised manuscript): “… that when NOx concentration is very low…” Please specify how low is considered as low.
Line 72-74: “… the stability of the interaction result of different pathways…” I am not sure what this means. Please clarify or rephrase.
Line 92: Please indicate the pressure altitude of the model top.
Line 116: I could be wrong but I don’t think SSA is defined.
Line 146-148: The authors tested two outdated surface seawater iodide parameterizations (Chance et al. 2014 and McDonald et al. 2014) even though a more advanced data product is available (Sherwen et al. 2019). The authors argued that “Since the reported iodide values by Sherwen et al., (2019) lie between those calculated values according to parameterization of McDonald et al. (2014) and Chance et al. (2014), we chose the latter two to conduct sensitivity simulations.” Do keep in mind that the spatial distribution and dynamic range are also very different in Sherwen et al. (2019), especially in the tropical/subtropical western Pacific. I will not ask the authors to perform additional simulations at this stage, but this remains another apparent limitation of this study (both surface seawater parameterizations tested in this work are outdated) that should be noted in Section 3.5 (Limitations of this work).
Line 149-151: I think Ordóñez et al. (2012) parametrization essentially has constant values in the subtropics and high latitude regions (e.g., north of 20N). I am not sure if simply scaling up based on global emission makes much sense, since much of the discrepancy is driven by spatial variabilities. It would be great to compare the scaled surface seawater halocarbons to the surface seawater observations in this region (e.g., Fuhlbrügge et al., 2016, Fiehn et al., 2017). But I do realize that these halocarbons play a relatively minor role as revealed in this work. Nevertheless, it is worth mentioning this in Section 3.5 (Limitations of this work) that the halocarbons in this region (tropical western Pacific) remains poorly understood which is potentially important for stratospheric injection.
Line 324: “Since these factors are generally species-related…” What factors? Please clarify.
Line 355: Please remind the readers where the Greater Bay Area is. Consider labeling that in the map.