Dear Elisabeth

I have an additional report from referee nr. 2, which suggests some minor revisions related to the moisture source diagnostics and I provide another review from my side, which concludes that substantial revisions (they are in between minor and major) are required to address mainly two important issues.

1) Objective and scope of this paper. I think you cannot have "stable oxygen isotopes" in your title and then say in your replies "This paper is neither meant to be about stable isotopes nor about moisture source analysis ...". If stable isotopes are in your title and in the 2nd sentence of your abstract, then this paper is about stable isotopes. Your section 3.2 is called "Stable isotopes", then 4.1 "Precipitation and isotopes" and again 5.3 "Stable isotopes". However, I agree with you that the paper itself does not show a lot about stable isotopes. Only Fig. 10 contains isotope data and the figure is not discussed in detail but rather you refer to the paper by Stenni et al. for an interpretation of the isotope measurements. I therefore think that the issue is with the structure of your paper, which needs to be improved. Please distinguish much more about the motivation part (interpretation of isotope measurements, but the actual discussion of these measurements is in another paper) and the real novel content of this paper (meteorological characteristics of the two different years and potential implications for stable isotopes). It is my impression that the stable isotopes should vanish from the title, they should appear in the abstract only as a motivation, and I don't see why you need so many section heads about stable isotopes. Also, I am not sure that Fig. 10 should be in this paper, I assume that it appears again in Stenni et al. and is discussed there in more detail. I understand that you submitted a series of related papers at the same time. This can be an excellent thing to do but it clearly has the danger to confuse the reader about what is really dealt with where. This should become much clearer in the next version.

2) Clarity of the moisture source method. Maybe for you this is appears to be a detail. But two reviewers and myself are confused. We don't understand the method and your replies don't help to understand it better. An essential aspect of science is reproducibility and therefore if three colleagues who work in related fields try to understand and fail, then something is not good. Please decide whether the moisture origin aspect is relevant for your study. If yes, then you should describe your technique in an understandable way. If not (not essentially) then I suggest that you omit the discussion of the moisture sources in this paper.

3) Some more specific points:

a) You write "... and the transport occurred lower in the atmosphere (approximately at the 500-hPa level) than previously assumed in ice core studies. Since the humidity calculated along the 300hPa-trajectory was already comparatively low (absolute humidity a factor 10 lower at 300hPa than at 500hPa) we assume the 500hPa level as representative for the main moisture flow, which is, of course, not restricted to the 500hPa level, but occurs in a thicker layer that includes the 500hPa level." I am very surprised about this. Of course 300 hPa is much too cold and dry to be relevant for moisture transport. But 500 hPa is still not very typically the strong moisture fluxes occur, they are much lower in the atmosphere (see the many studies about atmospheric rivers and tropical moisture exports). The assumption that the 500 hPa flow is representative is very ad hoc and not well justified. Also at some point the moisture source occurs at the ocean surface (about 1000 hPa), and therefore the moisture first must raise from the surface to 500 hPa. How can you consider this by looking at only the 500 hPa flow?

b) "Different from the approach of Sodemann and Stohl (2009) and Sodemann et al. (2008), who calculated 20-day back-trajectories, for a 5-day trajectory it is possible to comprehend the dynamics of the synoptic situation that causes the precipitation. That way the trajectory results can be cross-checked with the geopotential height fields." This requires further explanation. Are you just looking at the trajectories and the 500hPa field at some point in time and interpret the synoptic situation? This carries a large element of subjectiveness not present in other methods. Important is to remember that the 5-day trajectory may be helpful in determining the regional flow pattern, but not tell about moisture sources.

c) "Even though the trajectory not explicitely deals with moistuer, it gives information about the origin of the moist air mass. The northernmost “point” of the trough that causes the northerly flow to Dome C is supposed to be the northern limit of the potential moisture source since no substantial meridional flow is observed north of this limit." The 5-days limit appears arbitrary, and previous studies have shown that moisture travels more (much more) than 5 days in this region. At best you could identify a moisture direction, but not a moisture source. Remember that the moisture has to somehow reach from the surface to 500hPa, which can be associated with substantial horizontal transport. See also the concern from reviewer nr. 2.

d) "(The 500hPa trajectory seems to have some inconsistencies (e.g. kinks) on the 5th day, which should not be over-interpreted). Whereas it is not possible to exactly determine the moisture source (under the simplifying assumption of a single moisture source) with this simple method, the information is sufficient to distinguish between a source in the Southern Ocean and one at middle latitudes, which is most important for ice core interpretation and for simple isotope modelling." How should this be possible if the trajectories all end after 5 days? The trajectories may simply not be long enough to reach to the actual moisture sources.

e) "Because of the more meridional flow and thus more northerly (and warmer) oceanic moisture source, the initial 18O is already higher than on average and the condensation temperature at Dome C is above-average during the precipitation events as well." Here the simple moisture source approximation results are considered as if they were actual oceanic sources. This is in disagreement with the reply to the reviewers and needs moderation.

f) In the Conclusions: "Another implication for ice core interpretation derived from the present study is that a more northern moisture source does not necessarily mean larger isotopic fractionation (which is usually assumed in ice core studies (e.g. Stenni et al., 2001; 2010). Even though the temperature at the main moisture source is higher than on average for a northern moisture source, the depletion in heavy isotopes is comparatively small because the temperature at the deposition site is also clearly higher than on average due to the warm air advection, which reduces the temperature difference between the moisture source region and the deposition site, thus the amount of isotopic fractionation." If the paper is neither about stable isotopes nor moisture sources this paragraph needs to be removed. Otherwise the reviewer comments need to be taken seriously. Here, the moisture sources identified by the simple method are interpreted as if they were evaporation sources.

g) "Altogether, this means that the relationship between air temperature and stable isotopes of Antarctic precipitation/ice is anything else but straightforward, since the isotope ratio measured in an ice core (or in the snow) is the result of a complex precipitation history that is strongly influenced by the synoptics and general atmospheric flow conditions, followed by post-depositional processes. Without thorough knowledge of all the processes involved a quantitatively correct derivation of paleo temperatures from ice core stable water isotopes is thus not possible." The final conclusion is also about stable isotopes and ice cores. How is that possible if the paper is not about stable isotopes? Please reconsider how your phrase your final conclusions.

With best regards,
Heini

Dear Elisabeth

Many thanks for the revisions. I am now happy to accept the paper for publication subject to a few mainly technical corrections that will not require another round of review. Please consider the following points when preparing the final version of your paper:

line 36 and line 103: striking --> strikingly

line 64: state --> stated

line 67 and in many other places: references should be in chronological order!

line 105: reports --> reported

line 117: Lorius --> Lorius et al.

line 143: explain what AWS means

line 174: I still find this statement at least surprising: 500 hPa seems to me a rather high level for strong moisture transport (I expect it to be at lower levels, e.g., 800 hPa). Obviously you claim the opposite that other studies assumed the transport of moisture to occur at higher levels ... can you give references for this?

line 279: I don't understand the intention of the sentence: "... precipitation ... on 9 Feb ... followed by ... on 10 Feb ... stems from one event around 9 Feb" - this seems to be obvious to me, what is really the point?

line 362/364: I think the word "composite" is confusing here, you just calculated the monthly mean(?)

line 460: state --> stated

line 516: now --> snow

With best regards,
Heini Wernli