Dear Authors,

collecting the comments of the three different reviewers, it still remains a different task to give a recommendation for this manuscript. Overall, the manuscript provides important and interesting material, with which there is nothing wrong, but it provides just too much information, presented in a very descriptive way ("a work summary, rather than a synthesized scientific paper", as quoted by a reviewer). Therefore, I'm afraid that a reader will loose its interest when struggling through e.g. all the descriptions of the differences seen in the figures of global IWV means and trends. And this would really be a pity, given the workload put in the analysis. So, I follow the referee #1 that the manuscript is still too long and should be considerably shortened. Please follow the general comment of this referee regarding Sections 4 and 5. I will also give some specific indications on which parts could be significantly shortened later on. But furthermore, I would also go through your manuscript once more and ask yourself at every sentence the questions: "Is this sentence really necessary? Does it provide new information? Has the information provided not already been given at another location in the manuscript?"

Secondly, I also think that you did not take into account well enough the comment raised by Referee #2 (who also asked for a major revision, but unfortunately was unable to review the paper again during the summer break) about the focus of the paper. Yes, you rewrote parts of the introduction, shifting the focus to the IWV analysis based on the two (recent) reanalyses (page 2, line 33 - page 3, line 10), but this shift of focus is not consistently kept throughout the analysis. For instance, in Section 3, you should then primarily discuss the differences in the means and variability between the IWVs from the reanalyses, and in regions where you find discrepancies between both reanalyses, use the GPS dataset to understand and explain those discrepancies. Here, also the reference to the analysis done by Trenberth et al. 2011 is important. Now, in its present form, two third of the Section (pages 7 and 8) deals with GPS - ERA-Interim IWV differences, while the focus was said to lie on the reanalyses. These two pages should hence almost completely be dropped from the regular text, instead I would devote an entire appendix on GPS site specific findings (with a description (and explanation) of sites for which the means, standard deviation and trends deviate from these of the reanalyses). In this case, a reader with a GPS background will easily find his/her way to relevant information for his/her research. The same remark about the inconsistent focus applies to the trend description sections 4 and 5.1. As your focus is on the comparison of the reanalyses, it is really illogical to start the description the trends with the comparison between GPS and ERA-Interim (Section 4). From my point of view, it seems more logical to start the analysis with the comparison of the ERA-Interim and MERRA-2 trends for the 1980-2016 time period, and then constrain to the 1995-2010 time period in which the GPS dataset can be used as external comparison (as outlined on page 3, lines 5-6). But here again, I would move GPS site specific findings about trend differences with ERA-Interim (and why not with MERRA-2) to the dedicated Appendix.

Now, I will give some specific comments, in particular highlighting the parts of the paper that can seriously be shortened to my opinion.
* page 1, lines 12-13: in the abstract you mention the link with ENSO, while this is only a secondary outcome of your paper (as a matter of fact, you have never shown it). So drop it.
* page 2, lines 5-13: also not very relevant for your analysis here.
* page 3, lines1-4: move to section 2.1
* page 4, lines 7-10: might be moved to the GPS site-specific appendix
* page 6: lines 14-19: Is this information (mentioned, not shown) really important for your paper?
* page 6, lines 24-26: how does this finding compare with other studies (e.g. Trenberth et al. 2011? Perhaps you should mention this at this location).
* page 7, lines 4-25: this information might be shifted to the proposed appendix
* page 7, line 31 - page 8, line 28: this information might be shifted to the proposed appendix, possibly just provide a summary of a few sentences in this part of your regular paper.
* Sect 4: move after Section 5.1 and shift the bulk of the text (especially page 9, line 15 - page 10, line 15) to the proposed appendix.
* page 11, lines 14-22: please be aware of some duplication of text with sections 5.1 and 5.2
* Sect 5.1: I would start this section with the paragraph on page 13, lines 19-33 (but only for the long period), which is really well written, a really good summary without too much obsolete information.
* page 12, line 15 - page 13, line 12: these paragraphs could be considerably be shortened! You just have to mention where the ERA-Interim and MERRA-2 trends are opposite and what the trends of the GPS sites in those regions are.
* page 16, line 32 - page 17, line 11: this paragraph is very hard to follow, as it is a mixture of IWV trends, T trends, IWV-T correlations, both for the short and long period and also for the seasons! Could you not highlight the most important findings instead of mentioning them all?
* page 18, lines 5-12: In the beginning of the summary, you state that your focus are the modern reanalyses (line 3). But, in the following lines, you give the results about the comparison between GPS and ERA-interim.

I want to congratulate you with the large improvements made to the paper. To my opinion, the paper is now written much fluently, the focus clearer and it also better incorporates the remarks/suggestions given in the different reviews. I only have some small suggestions for corrections/adjustments:
* on page 2, lines 3-4: this sentence has some issues. First, specify to what "This" refers to. Secondly, it's an evidence that IWV is highly variable due to the short residence time of water vapour in the atmosphere: you make two times the same statement here. Rewrite this sentence please.
* page 2, line 29: a "valuable validation dataset" instead of "a valuable validation data"
* page 3, line 12: NASA is used here for the first time, so spell out (although everyone knows NASA).
* page 6, line 3: "zero" instead of "null"?
* page 6, line 25: "their values do not" instead of "their values don't"
* page 7, line 22: "Significant trend differences" instead of "Significant differences"
* page 7, line 28: spell out NOAA and SST
* page 7, line 26 to page 8, line 11: it might be a good idea to mark the Maritime Continent and North Africa with boxes on the discussed plots.
* page 8, line 7: "extends southward" instead of "extents southward"
* page 8, line 8: "see also further on Fig. 8"
* page 8, lines 21-22: You might change into "However, the amount of assimilated data over the Antarctica's ice sheet may differ between the reanalyses, which is actually not documented."
* page 8, lines 25-26: "A striking feature seen in both reanalyses is their relatively larger magnitude compared to the monthly trends." You might comment here if this might be related to the fact that for the seasonal trends, you calculate trends based on one value a year, and for the monthly trends, one value every month is used for the trend calculation.
* page 9, line 13: Trenberth et al. (2005) "suggested" instead of "suggests"
* page 9, line 28- page 10, line 5. I got the impression that this discussion only takes ERA-Interim into account, not MERRA-2: you only refer to the ERA-interim subfigures of Fig 8 and at the beginning of the page 10, you note that "For JJA, all continental areas show a significant warming, with the exception of parts of Antarctica, and a small area over northern Australia, where a cooling is also displayed, albeit not significant", a statement which is not true for MERRA-2. Please be more general in this paragraph. But also not too general, because at page 9, lines 30-31, you write: "Over land, all areas show an increase in temperature, except the high latitudes of the southern hemisphere". It should be noted that also over large parts of the Asian continent, the temperature decreased.
* page 10, line 30: The different IWV trend estimates between the two periods "are" instead of "is"
* page 11, line 11: "their trends over and around Australia present different patterns (Fig 10)". Please specify which field and DJF/full time series.
* page 14, line 6: add "(" before see Appendix B).
* page 14, line 27: "below" instead of "under"
* page 15, line 1: add "with respect to the Theil-Sen method" at the end of the sentence.
* page 15, line 11: "do not agree" instead of "don't agree"
* page 15, line 18: "located above 1000 hPa" (or superior to) instead of "located below 1000 hPa".
* page 17, line 15: "coincides" instead of "coincide"
* page 17, line 18: "do not seem" instead of "don't seem"