Review of ‘Towards a holistic understanding of blocked regime dynamics through a combination of complementary diagnostic perspectives’ by Seraphine Hauser, Franziska Teubler, Michael Riemer, Peter Knippertz and Christian M. Grams
General comments
The paper constitutes an impressive piece of work tackling one important outstanding problem in dynamical meteorology, namely the dynamics of atmospheric blocking. Part of the problem is the lack of agreement between definitions and approaches to the problem. In this paper the authors present an attempt to integrate several of these approaches in a step towards linking the different aspects of atmospheric blocking. From this point of view the importance of the contribution is very clear as is the fit of this work into the scope of Weather and Climate Dynamics.
I give below a list of specific and technical comments that I believe can improve the paper by making it more understandable. Some of the most important comments are related to the projection onto weather regimes. In particular I find puzzling the meaning of the projection of tendencies although I suggest a way to present this that makes sense. My intention is not to impose this view, but I certainly think it would be worthwhile for the authors to expand on the explanation of their approach. Some other important comments are related to the interpretation of the results. I got confused at times and this will probably be reflected in my specific comments. To reduce confusion it might be worth being more rigorous in the labelling of the stages and substages that occur during the evolution of the case study.
Once these comments are considered I will be able to fully recommend the article for publication in this journal.
Specific comments
L83-84: I can see that the projection (correlation) of PVAs with a mean regime PV pattern will increase as a PVA co-locates over the location of the regime pattern, but it’s difficult to see that the same will occur in the case of PV tendencies.For these the regime patterns will need to form some sort of complete set, akin to Fourier modes or spherical harmonics or even EOFs, but I don’t think this is the case here, is it? Could you explain a bit more on how this approach is the right one? (This comment is related to those to Eq. 6 and L226 below).
L114: Is the PV inversion part of the Teubler and Riemer method? If so, add a reference to their work, or make this clear when you introduce the method in Section 1.
Equation 3: No definition has been provided for v_0. Is it the result of the inversion of q_0? This needs to be explicitly stated.
Equation 6: I find it puzzling that both q^L but especially its tendencies can be projected onto the same weather patterns. I find it similar to projecting q^L onto weather patterns defined in terms of a completely different variable, e.g. original weather patterns defined in terms of Z500. Why does it work? Can you discuss more on this?
L226: ‘The observed temporal evolution of P_{q^L} agrees very well with the diagnosed evolution of [the sum of the terms in Eq. 7’. I agree with the sentences as it is, as indeed the time derivative of Eq. 6a (for P_{q^L}) is Eq 6b, i.e. dP_{q^L}/dt = P_{\partial q^L/\partial t}. Perhaps this is the approach to take to explain why the projection of the tendencies work. Having said that, I think there is something missing between this sentence and the next. Between which two variables is the difference of 0.07 d^{-1} mentioned in the text?
L244-245: I got confused here. Earlier in L240 it is said that a weaker threshold is used to increase the PVAs’ spatial extent, but then it says in L244-245 that it is advantageous to not group together individual anomalies in a single large anomaly. I find these two sentences contradictory, but I have the suspicion that I’m missing something.
L261-264: This paragraph needs rewriting. The term Bnd is suddenly introduced without indicating that this will appear later in Eq. 9. A similar issue occurs with the term RES, which again does not appear until Eq. 9. Perhaps the only thing required is to move this paragraph to after that equation.
L474: I’m not sure I agree with the statement on the baroclinic and divergent tendencies. In the second part of the active life cycle the baroclinic tendency has an important positive contribution, whereas the divergent tendency has a small, negative effect.
L489: I agree that the non-radiative diabatic tendencies are mostly positive, but I think it is worth explicitly noting that they are also very small.
L499: The divergent PV tendency is put as the leading contribution and the quasi-baroclinic one as the secondary. However, going by the bars in Fig. 11b I would consider them the other way around, or perhaps both as the leading terms.
L517: ‘... all prominent peaks […] are associated with an increase…’ This is really difficult to judge. Perhaps be more explicit on which ones you consider the most prominent.
L547: It would be interesting to expand the discussion on the case study. The authors describe that the PVAs are advected into Europe and do not build up locally. How common, and therefore, how representative such a case is?
Figure B1 caption: I’m not sure the description of the lines in the caption corresponds to the legend in the figure. The observed line is described as black, dashed, but there is no black, dashed line. There is also a pink line mentioned which I can’t see.
Technical comments
L26-27: ‘The weather regimes…’ Move this sentence to later, possibly to current L78 once the set of patterns to be used in this work has been introduced. Otherwise, it looks a little out of place. Alternatively, you could expand on the general discussion on weather regimes to explain the differences between them, but I don’t think this is really necessary here.
L90: When you say ‘now generally’ do you actually mean ‘here’ as in ‘in this work’?
L98: I suggest putting ‘by combining the three perspectives’ between commas.
L105: Add ‘the’ between ‘is’ and ‘content’. You could consider ‘constitutes’ instead of ‘is’.
L118: Just for clarification, are the data valid at 2, 3, and 4 UTC taken from the forecast starting at the previous analysis time, i.e. in the example from the 0 UTC forecast?
L126: Should it say ‘isentropic wind vector’?
L129: What are the sources and sinks of non-conservative momentum apart from friction?
L133: Delete ‘mathematical expression used here:’
L240: I’m not sure what ‘respectively’ indicates here? What corresponds to what? I think it could be deleted without affecting the meaning of the text.
L259: What isentropic levels are those mentioned in this line? Are those contained within the 150-500 hPa layer? Please clarify.
L262: Change ‘residuum’ to ‘residual’.
L274: Should it say ‘v . nabla q_0’ instead of ‘v . q_0’?
Figure 5: The purple lines appear as red/magenta in my screen and hard copy. If possible change perhaps to a darker purple or a different more contrasting colour. The WCB trajectories partially obscure the fields underneath due to the vast amount of them. Perhaps plotting less of them could make the figure clearer? Just to clarify, these trajectory intersection points do not all belong to the same WCB, do they?
L322-323: How is the amplitude measured in PVA? Should it say ‘measured by the maximum value within the PVA’?
L365: ‘We already anticipated’ gives the idea that something was predicted. I’d suggest changing it for ‘We have already shown’.
L372: I think it should be Fig. 6b.
L375: Change ‘an’ for ‘a’.
Figure 6 caption: Define DIAG.
Figure 8 caption: Two queries here: (1) In what sense is there a centre of mass? Should the tracks be defined in terms of centroids, or is some atmosphere mass or density involved in the location of the tracks? (2) How is the ‘mean frequency’ defined? I understand it is some sort of measure of persistence but I’m not quite sure what it is? (See also comment to L413 below).
Figure 8b: It would be useful to add dates, or just the day number, to selected events mentioned in the main text.
L413: What is the ‘frequency maximum’? What is it that it’s being counted?
L421: There are two jumps in the track, one northwards and one southwards. I assume the one discussed here is the one southwards…?
L450: Do you mean ‘upstream’?
L455 and L457: There is slight repetition between these two lines on the amplification of the PVA.
Figure 10: The PVA_qL^- phase could be indicated in the figure with vertical lines.
L468: Is the change in the character of the baroclinic tendency from negligible to persistently positive associated with a particular synoptic system or event?
L470: Looking at Fig. 11c, I think it should say ‘with only a small negative net impact’.
Figure 12: It would be worth noting that the red curve is the same as that in Fig 10b. The authors could also note that the NON-CONS curve in Fig. 10c is the same as that in Fig. 10b, although of course this is more obvious.
L586: I think it should say ‘However, a few [...] events…’ rather than ‘However, few [...] events…’ As it is written, the idea conveyed in my opinion is that the splitting events are not important at all.
L604: Add ‘the gap’ between ‘bridge’ and ‘between’.
L645: Delete ‘also’. |
