|The authors have addressed the reviewers’ comments and revised the manuscript. Their results demonstrated the influence of Baltic Sea ship emissions on air quality and deposition under the SECA regulations and the NECAs in the future. The additional analyses of SO4 due to ship emissions and changes in ozone for the two seasons provide more comprehensive understanding of the ship emissions impact on air quality. However, I still have a few concerns as described below:|
1. Page 6, line 30-34: The results showed that the measured and modeled fraction of SO4 in PM2.5 only increase slightly with the Present_HiSulphur scenario. I suggest the authors provide possible explanations for the linkage between the SECA regulation and changes of SO4 and PM2.5 (Present_HiSulphur-Present_Base).
2. Page 8, line 28-31: The statement “In summer the increase caused by titration around the English channel…..dominates the annual values.” is confusing, as NOx titration leads to ozone reduction. Is the increase of SOMO35 and annual ozone over English Channel contrast to decrease of ozone for the rest BAS caused by reduction of titration? If it is what the authors mean, it would be helpful to clearly state the increase “of ozone” (SOMO35 and annual averaged ozone) and “reduction” of titration.
3. Page 8, line 31-34 & Page 9, line 1-2:
(1) It would be helpful to remind reader by referring the figure in detail for better understanding the discussion. For example, for the paragraph “As shown in Figure 4….are higher in 2030 (but SOMO35 is reduced)”, you can add “(green bar)” to specifically refer the bar in Figure 4.
(2) The statement “In 2030 the additional emissions from BAS shipping…..except Denmark” does not match what Figure 4 shows. This sentence seems to discuss the blue bar (contributions from BAS in 2030) in Figure 4 but all the countries have increased SOMO35 and annually average ozone due to BAS ship emissions in the future, including Denmark. Also, the following sentence “Here average ozone decreases (in contrast to the case in 2016, where SOMO35 increases when adding the emissions from BAS shipping)” is not clear either.
4. Page 10, line 19-25: The authors discussed whether the target set by IMO could be achieved in the future based on the results of this paper. Here the connections between the IMO target and the results of this paper are not clear, given the IMO target described here mainly focus on CO2 emissions and GHG emissions from shipping, while this paper focused on NOx, SO2, and PM2.5. The linkages between IMO target and the findings in this study can be stated more clearly.
1. Page 3, line 1: Please specify what LNG stands for.
2. Page 17, Table2: The Base-model calculated values of NO2 and SO2 for the site Uto are negative.
3. Page 18, Table2: The HiSulphur-model calculated value of SO4 for the site Rao is negative.
3. Page 23, Figure 4: The figure descriptions and legends are not consistent (green bar should be Present_Base – Future_Base; blue bar should be Future_Base – Future_NoShip).