Assessing the uncertainty of glacier mass-balance simulations in the European Arctic based on variance decomposition

Sauter, T.; Obleitner, F.

doi:https://doi.org/10.5194/gmd-8-3911-2015

Articles | Volume 8, issue 12

https://doi.org/10.5194/gmd-8-3911-2015

© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/gmd-8-3911-2015

© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 8, issue 12

Methods for assessment of models

|

10 Dec 2015

Methods for assessment of models |

| 10 Dec 2015

Assessing the uncertainty of glacier mass-balance simulations in the European Arctic based on variance decomposition

T. Sauter and F. Obleitner

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Final revised paper (published on 10 Dec 2015)
Preprint (discussion started on 13 Mar 2015)

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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- Supplement

RC C571: 'Review of the paper "Assessment of the uncertainty of snowpack simulations based on variance decomposition" by Sauter and Obleitner', Anonymous Referee #1, 29 Apr 2015
- AC C1572: 'Responses to comments from Reviewer 1', Tobias Sauter, 03 Aug 2015
RC C622: 'This is the review of the paper by T. Sauter and F. Obleitner entitled "Assessment of the uncertainty of snowpack simulations based on variance decomposition".', Anonymous Referee #2, 05 May 2015
- AC C1583: 'Responses to comments from Reviewer 2', Tobias Sauter, 03 Aug 2015
SC C650: 'Review of Sauter and Obleitner (2015, GMD Discussions)', Mark Raleigh, 07 May 2015
- AC C1593: 'Responses to comments from Reviewer Raleigh', Tobias Sauter, 03 Aug 2015

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

AR by Anna Wenzel on behalf of the Authors (04 Aug 2015) Author's response

ED: Referee Nomination & Report Request started (17 Sep 2015) by Philippe Huybrechts

RR by Anonymous Referee #1 (06 Oct 2015)

RR by Anonymous Referee #2 (06 Nov 2015)

Suggestions for revision or reasons for rejection

The updated version of this manuscript has significantly improved on most of the issues mentioned during the first round of reviews. The topic was already very interesting and thanks to the much improved methodology section the paper should become very useful to lots of people working with energy balance modeling. However, a few remaining issues should be improved before final publication.

First, the manuscript still requires English editing. This does not present a challenge for understanding the authors but is still distracting enough that this should be fixed. Quite a few sentences should be rephrased in a more natural way and the authors should refrain from using "e.g." too often.

Then, some restructuring is still required. For example, in the section 2.1 there are redundancies in the description of CROCUS between the beginning and the following paragraph (lines 23 and up should be merged with lines 12 and up). In section 2.3 (reference runs), the discussion about the initial temperature profile at line 9 should be grouped with its justification starting line 20. And finally, the whole "discussion" section is in serious need of restructuring. Although it is interesting, it is very long and lacks internal structure. Therefore, creating sub-section within section 4 would clarify its structure and help the reader keep track of which points are being discussed. This could also help reduce somewhat the usage of acronyms that, although they have been previously defined, tend to force the reader to go back to their definitions every now and then. Special care should be taken regarding the short wave radiation discussion: what is written on page 27, lines 25-26 tend to be inconsistent with the proof that is given on next page 28, lines 3-14. The latter seems to be the right explanation (or the dominant effect) and therefore should take precedence.

A few more things should also be explained: even after carefully reading the paper, it is still not clear what has been modified in Crocus compared to its standard version. This should be clarified. For example, the discussion about the conversion from snow depth changes to water equivalent: is it performed within Crocus with its own routines or is it performed offline in an ad hoc re-implementation of some parts of Crocus? If this would be the case, how is the settling handled? Another thing that could be improved: although the reviewer is very grateful for the great explanations about the Global Sensitivity Analysis (section 2.4), the transition from SA to GSA could be better shown. One starts reading about SA and suddenly realizes that it shifted to GSA. One sentence at the right place might be enough to call the attention of the reader to what is changed in order to switch to GSA. In the same section, on page 14, it would be great to explain how are the A and B matrices filled (or link it to the discussion about the Sobol sequences), to be on the safe side.

Finally, the conclusion seems to stretch the results a little bit beyond my comfort zone. When the authors conclude about altitudinal trends and/or different zones on the glacier, one should not forget that this study has been performed at only two stations (and one year). Concluding about "the lower elevation station" versus "the higher elevation" is safe while generally concluding about altitude trends is more of an extrapolation.

Some detailed comments:
* please, keep in mind that language editing is required!
* on page 3, line 15: what do you mean by "more and better data to constraint [...] results of the simulation"? Although it makes sense for the initialization or forcing, it is not a direct link to the results!
* on page 5, line 7: there is an extra "(" in the middle of the line;
* on page 5, line 25-26: does Crocus use molecular conductivity or bulk conductivity?
* on page 6, line 1: there is an extra ")";
* on page 6, line 21: missing "t" in "budget";
* on page 7, line 2: misspell "respectively";
* on page 7, equation 3: consider defining "P";
* on page 9, line 7: there is a lonely "2" at the end of the line;
* on page 16, line 17: idem;
* on page 17, lines 8-9: basically, the density compensates for the albedo parametrization short comings, right?
* on page 22, line 7: very unclear... what are these other directions?
* on page 22, line 27: what do you mean by "The traces"?
* overall, it seems that there are no liquid precipitation measurements. Maybe this should be mentioned on page 24 in the discussion about the precipitation impact (ie in the summer, this impact won't be shown since it is not even measured)
* on page 25, lines 3-7: please clarify.
* on page 26, lines 1-3: this is unclear.
* on page 26, lines 12-13: it seems hard to believe that the impact of the grain shape due to wind drift would be significant compared to the turbulent fluxes!
* on page 27, lines 4-6: please clarify: are the air temperature measurements ventilated?
* on page 27, lines 7-8: what do you want to tell us?
* on page 29, last line: what are "the remaining ones"?
* on page 30, line 1: misspell "for"

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ED: Publish subject to technical corrections (23 Nov 2015) by Philippe Huybrechts

AR by Tobias Sauter on behalf of the Authors (01 Dec 2015) Author's response Manuscript

Short summary

Even small errors in observational data can have a profound effect on snowpack simulations, which dilutes our confidence in the results. This paper aims at quantification of the overall contributions of these errors on the uncertainty of snowpack simulations in Arctic environments. The analysis demonstrates that the uncertainties in the data can have a profound impact on glacier mass balance estimates.