Changes in Tropical-Cyclone Translation Speed over the Western North Pacific
Round 1
Reviewer 1 Report
General comments:
The paper contains two parts: the authors first examine the trend of tropical cyclone translation speed (TCS) for the western North Pacific (WNP) region; then they apply the trends to three parameters that imply the impact of TCS on the ocean. The first part may provide some useful information and can be one concise paper. I recommend that the authors should focus on the first part and discuss the results together with the previous studies. The second part, on the other hand, does not fit into the paper: first, it based on an un-confirmed ongoing debate about the TCS; secondly, the implication of these trends of TCS, for example, 10% TCS slowdown, on the ocean via those parameters can be described very shortly. Thus I think this part is not interesting enough and makes the paper longer than necessary. You can briefly mention the implication of the TCS trend and the impact on the ocean in the discussion or introduction (to highlight the need for the study of the TCS), or you can put it in a different paper with adequate analysis.
L34-43: These discussions do not fit into the topic of the paper and distract the readers. The authors should shorten or get rid of those and go directly to the discussion about the trend of TCS. L44: Another important point discussed by Moon et al is the data missing data in the pre-satellite era. I recommend that the authors should pay attention to the discussion about the trend of TCS. L53-62: This is a tutorial about the interaction of the cyclone and the ocean, but it does not go with the study of this paper. I recommend getting rid of this paragraph. L65-67: How does your study provide something news to the previous studies, which also include the WNP region? Do you use a different dataset that may overcome the data problems? Do you carry out a more detailed analysis? What is the goal? L78-79: Have you noted that the two CMA dataset in [35] and [36] are different (notice the number of TC in the pre-satellite era)? Where did the author mention that the CMA dataset is “more complete and accurate”? I think you should put some discussion in the introduction as well. L95-101: You should explore more on these questions: how are these results different from the previous studies and what is the possible reason. L110-117: you can just note that the trend of TCS over the ocean contributes mostly to the overall trend, and can get rid of Fig. 2 and Fig. 3(the trend TCS on land is not reliable anyway). L135-144: this is interesting that you show there is evidence in the slow down of the circulation. But your discussion needs to follow the previous studies: do you provide some new evidence to confirm that there is a real downward trend in TCS in the pre-satellite era? L169: What is the size of the box that you used to calculate the distribution? It seems that the box size is too small and the data is not dense enough so that the distribution looks spotty. You can make the plot more interesting by plotting the average translation vectors on top of that. L172-176: How do you interpret the red line? Get rid of it if there is no useful information. L173 “The black line shows the changes in the mean…”, should be “The black line shows the mean …”. L205: Why doesn’t the mean TCS (black line) match with the frequency distribution (shaded), especially in the bin of 10-20 m/s L223-305: As mentioned above, this part should not be in this paper. L306-: The rest of the paper (and the abstract) should be carefully revised according to the changes in the previous parts.
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
This paper presents an interesting analysis of the changes in the average translation speed of tropical cyclones over the Northwestern Pacific Ocean. The research presented expands on previously published research with a more specific focus on the region of the Northwest Pacific. There is sufficient new content and analysis to warrant publication. The authors seem to reach four important conclusions. First, the average translation speed of tropical cyclones over that basin has declined since 1949. Second, almost all of the decline occurred in the period from 1949-1981. Third, most of the decline occurred at lower latitudes. That is relevant because the translation speeds were already slower than at higher latitudes. Fourth, most of the decline occurred with tropical cyclones which were at typhoon intensity.
In Section 3.1 the authors properly note that the time period around 1981 coincided with more widespread availability of geostationary satellite imagery. They also note that this increased the number of fixes of centers of tropical cyclones in the database and that the increase could potentially affect any trends in the time series. The authors present the percentage of points over the oceans before and after 1981 to support their analysis. It might be useful to present the actual number of points rather than percentages to illustrate the increase in fixes.
Overall, I found the paper interesting and informative and worthy of publication.
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
Please see attached review (MS Word Document).
Comments for author File: Comments.pdf
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
I really appreciate the effort of the authors to revise the paper significantly.
There are few minor grammatical errors left throughout the text, you should check thoroughly for the final version.
For example
frequency of typhoon -> frequency of typhoons, or typhoon frequency. typhoon category -> the typhoon category translation speed of typhoon -> translation speed of typhoons
Author Response
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Author Response File: Author Response.pdf
