Simulation Tool for Winter Navigation Decision Support in the Baltic Sea
Round 1
Reviewer 1 Report
Plaese check the attached pdf.
Comments for author File: 
Comments.pdf
Author Response
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Author Response File: Author Response.pdf
Reviewer 2 Report
The paper presents a novel and complicated simulation method for the winter navigation system in the Baltic Sea. This topic is very relevant, and the methodology is state-of-the-art. The manuscript is well prepared with good English language as well. Although the paper has its originality and potential in many aspects, the reviewer hesitates to recommend it to be published in its current shape. My arguments are listed as follows:
- The proposed simulation tool is a comprehensive tool with many aspects included. Because the methodology of discrete-event simulation and agent-based simulation is not commonly used tools, a section for an explanation of these approaches feels necessary. Also, because the simulation frame is comprehensive, it is preferable to be clarified with case studies to make readers understand the strength of the proposed simulation tool. However, achieving such a goal seems over-ambitious in one single article. The authors are suggested thus to consider dividing the manuscript into two articles: 1) Part I focuses on the methodology and simulation framework, and 2) Part II addresses mainly the application using case studies.
- My main objection goes to using h-v curves as one of the primary inputs of the proposed simulation tool. The author assumes a ship’s speed in ice, i.e., the h-v curve depends only on the ship’s dimension. This is questionable because the ship dimension only decides the resistance, while a ship’s achieved speed also depends on the propulsion, viz, the engine/propeller. In other words, if an h-v curve is to be used as the input, such an h-v curve should also consider ship power. In the current manuscript, the theoretical source of h-v curves has not been explained and it is unclear how h-v curves are connected to the different ship types or sets.
- About the icebreaker waiting time, it seems to start when the threshold speed is reached. However, what happens when the berths are occupied in the destination port? From the AIS data as input, how do judge the commercial ship stops because of ice or because of an occupied berth?
- My concern also goes to how the service time (gross berthing time) is handled in the simulation tool. To the reviewer’s knowledge, the service time is irrelevant for such a decision support system. Icebreaker assistance ends when the commercial vessel arrives at the port, while new icebreaker assistance starts upon the commercial vessel’s departure. If the service time can be anticipated in advance and reliable, it needs to be stated in the manuscript.
- Another question is about the ice condition. The author mentioned “equivalent ice thickness”, but has not clarified how it was derived. In Table 4, many other ice parameters are presented, without any explanation about how to convert these parameters to the mentioned “equivalent ice thickness”, which must be clarified!
- My final question goes to the DIRWAY which is another input of the simulation tool. Firstly, how are the data of dirways derived and what parameters are included except for the coordinates? Secondly, how are these DIRWAY data influence the efficiency in terms of speed or waiting time of the system?
Author Response
Please see attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
The revised manuscript has many aspects clarified and improved. The reviewer recommends thus for acceptance for publication.
