Interactive comment on “ Decadal evolution of ship emissions in China from 2004 to 2013 by using an integrated AIS-based approach and projection to 2040 ”

1. The cargo-based approach is very unclear. How do you get emissions other than 2013? This method is the key for the whole paper. The authors use only ten lines to give a very brief description. Without detailed data, it’s hard to prove the results are convinced. Response: In equation (2), cargo-based approach is to estimate emissions by transport volume, transport distance, fuel consumption, and emission factor. In the revised manuscript, we explain briefly the methods in determining transport volume and transport distance in lines 4-21 of page 6, and provide more detailed explanation in section 3 and 4 of the support information (SI), respectively. Determination of


Domain and ship categorization
Domain choose explain: According to the "United Nations convention on the law of the sea" approved by United Nations conference on the third law of the sea in 1982, which indicated that 200 nautical miles (Nm) exclusive economic zone (EEZ) belongs to the scope of the jurisdiction of the state, further explain in article 56 of the convention mentioned the right regulation of EEZ including the jurisdiction on the area of artificial islands, 5 installations and science research and Marine environmental protection fields, that is to say the research domain of ship emissions in China expand to 200 Nm zone is acceptable. However, science research does not mean the legislative power, have jurisdiction over 12 Nm of ship emissions control area (ECA) needs to be approved by IMO, e.g., Beihai ECA, Mediterranean ECA. The scope of these international ECAs are 200 Nm, which support the domain in this study, and also enhance the referable of this study. By the way, the domain chosen in this study 10 reflects our focus on densely populated areas and does not represent any national boundaries.
There were 18000 km coastline covered 31760 harbors in this region, which contains 5675 coast harbors and 2001 10kt carrier harbors. More detail for 10kt carrier harbors in table SI-1, SI-2.

AIS data information
According to the most advanced study (Liu et al., 2016), the introduction of automatic vessel position reporting systems has significantly reduced the uncertainty concerning ship activities and their geographical distribution. However, using shipping activity data for research remains a challenging task (Dalsoren et al., 2009;Liu et al., 2016). Different with Liu's study, this study established a model for ship activity data 5 calculation by using a continuously trajectories AIS dataset but not comprehensive in China Sea. Here I given a comparison of AIS data (Dalsoren et al., 2009;Liu et al., 2016) to demonstrate that the representativeness of our ship information dataset in China Sea is acceptable (table SI-5). The AIS was introduced by the IMO international Convention for the Safety of Life at Sea.
Which include shore-based and satellite-based data. The shore-based data is featured by high temporal resolution (every 30 seconds), but only covers ships less than 50 nautical miles from the shore. For the areas beyond 50 nautical miles, satellite-based data in 2-h interval was used. progressive reductions in NOx emissions from marine diesel engine, with more stringent controls being a "Tier Ⅱ" emission limit required for those marine diesel engines installed on or after 1 January 2011; then with the most stringent controls being "Tier III" emission limit for marine diesel engines installed on or after 1 January 2016. Marine diesel engines installed on or after 1 January 1990 but prior to 1 January 2000 are also required to comply with "Tier I" emission limits, if an approved method for that engine has been certified by 25 an Administration. On the other hand, fuel type and quality sulphur content as a major factor influencing the emissions of PM, HC and CO, and engine type also have effects on PM. As detail shown in table SI-7.
SO2 Emission = Fuel consumption × 2 × S% × R  OGVs, CVs and RVs mean Ocean-going vessels, Coast vessels and River vessels, respectively. c, d, e ME, AE and BE mean main engine, auxiliary engine and boiler engine, respectively.
Besides, the relationship of ship types to engine types and fuel types were the essential in emission estimation, shown in table SI

Uncertainties estimation
Uncertainties of emissions factors and activity time for estimation were shown as following.