Assimilation of snow cover and snow depth into a snow model to estimate snow water equivalent and snowmelt runoff in a Himalayan catchment

Stigter, Emmy E.; Wanders, Niko; Saloranta, Tuomo M.; Shea, Joseph M.; Bierkens, Marc F. P.; Immerzeel, Walter W.

doi:https://doi.org/10.5194/tc-11-1647-2017

Articles | Volume 11, issue 4

https://doi.org/10.5194/tc-11-1647-2017

© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/tc-11-1647-2017

© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 11, issue 4

Research article

|

11 Jul 2017

Research article |

| 11 Jul 2017

Assimilation of snow cover and snow depth into a snow model to estimate snow water equivalent and snowmelt runoff in a Himalayan catchment

Emmy E. Stigter, Niko Wanders, Tuomo M. Saloranta, Joseph M. Shea, Marc F. P. Bierkens, and Walter W. Immerzeel

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Final revised paper (published on 11 Jul 2017)
Preprint (discussion started on 26 Oct 2016)

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'Review of the paper “Climate sensitivity of snow water equivalent and snowmelt runoff in a Himalayan catchment” by E. Stigter et al. submitted to The Cryosphere.', Anonymous Referee #1, 30 Nov 2016
- AC1: 'Reply to Anonymous Referee 1', Emmy Stigter, 17 Mar 2017
RC2: 'Referee comment on "Climate sensitivity of snow water equivalent and snowmelt runoff in a Himalayan catchment"', Hendrik Wulf, 20 Feb 2017
- AC2: 'Reply to Wulf Referee 2', Emmy Stigter, 17 Mar 2017
RC3: 'Review “Climate sensitivity of snow water equivalent and snowmelt runoff in a Himalayan catchment” by Emmy E. Stigter et al.', Anonymous Referee #3, 27 Feb 2017
- AC3: 'Reply to Anonymous Referee 3', Emmy Stigter, 17 Mar 2017

Peer-review completion

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

AR by Emmy Stigter on behalf of the Authors (07 Apr 2017) Author's response Manuscript

ED: Referee Nomination & Report Request started (12 Apr 2017) by Guillaume Chambon

RR by Anonymous Referee #3 (27 Apr 2017)

Suggestions for revision or reasons for rejection

Re-Review “Climate sensitivity of snow water equivalent and snowmelt runoff in a Himalayan catchment” by Emmy E. Stigter et al.

General:
Most comments have been taken into account and the paper can be accepted. At the same time, I still think that the paper would benefit from a more extensive discussion and comparison of the climate sensitivity with similar results from other mountain regions. In particular aspects of precipitation versus temperature changes(e.g. [Schmucki et al., 2015]) at different elevations and changes in runoff timing (e.g. [Bavay et al., 2013]) can be compared. Such a comparison could be best done in Section 3.5.

A few minor mostly editorial things (page numbers from the “change track” version):

p.3, l.30: The last part of the sentence “and less snow cover” appears not to belong there

p.6 l.3: Can you give details on the temperature lapse rate errors since this is probably quite important.

p.7, l.14: “as” missing: … as long as ….

p.7, l.18: Albedo appears very low for fresh snow, can you justify?

p.9, l.24: When the “accuracy” is introduced in the equation, we should already have the exact mathematical definition (fraction of correctly classified pixels)?

p.9, l.31: The parameter C6 has not been introduced properly in the text

p.12, l.9ff: One thing, I have not understood, is the TT parameter. If this can be negative but only positive contributions are counted, should the parameter then removed? Please clarify the role of the TT parameter (better description / discussion). How can it be a “sensitive” parameter (you only picked those for calibration as explained in the text above) if you write that “the algorithm is insensitive”?

p.14, l.23: You should clearly say that this is the result from a very crude model parameterization

Bavay, M., T. Grunewald, and M. Lehning (2013), Response of snow cover and runoff to climate change in high Alpine catchments of Eastern Switzerland, Advances in Water Resources, 55, 4-16, doi:10.1016/j.advwatres.2012.12.009.

Schmucki, E., C. Marty, C. Fierz, and M. Lehning (2015), Simulations of 21st century snow response to climate change in Switzerland from a set of RCMs, International Journal of Climatology, 35(11), 3262-3273, doi:10.1002/joc.4205.

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RR by Anonymous Referee #1 (11 May 2017)

Suggestions for revision or reasons for rejection

Review of the revised version of the paper (Referee 1) “Assimilation of snow cover and snow depth into a snow model to estimate snow water equivalent and snowmelt runoff in a Himalayan catchment” by E. Stigter et al. submitted to The Cryosphere.

The authors have proposed a clear and detailed answer to all my points and to the points raised by the two other referees. The quality of the manuscript has been increased during the reviewing process.

I have a remaining concern about the choice made by the authors to change the title of the paper. Indeed, the authors have decided to insist more on the core of the study : the assimilation of snow depth and snow cover in a snowpack model to improve the quantification of SWE and snowmelt runoff. The climate section is now presented as a sensitivity experiment and the authors explicitly stated in their answer that this paper is not a climate change impact study. This is supposed to justify the choice of the simple delta method used in the climate sensitivity tests.
If the core of the study is the assimilation of snow depth and snow cover in a snowpack model, the authors should insist more on this aspect in their paper. For example, it should be more emphasized in the abstract and in the conclusion. So far, the conclusion has only been slightly changed compared to the initial version of the paper and it seems to me that the main conclusions of the paper still concern the climate sensitivity experiment.

Since the main focus of the paper is the data assimilation of snowpack data, I also recommend the authors to add the following additional information:

- The impact of data assimilation on SWE and snow melt simulation could be also evaluated using the surface temperature data as an indirect evaluation. This would allow the authors to compare the presence of snow in the simulation and in the observation. The two transects for surface temperature cover a large altitudinal range and two different slope aspects (north and south). This would be an interesting complement to the spatial evaluation that has been carried out with the satellites data (MODIS and LandSat).

- The assimilation of snow depth data is carried out at two stations including Kyangjin station where almost no snow is found in 2014. Snow depth observations are used to optimize the parameter C6 governing snow settling in the model. Therefore, the impact of assimilation of snow depth from Kyangjin station is expected to be quite low in 2014. Time series of observed snow depth on Figure 5 suggest that Yala Pluvio or Yala BC could be used to carry out the assimilation of snow depth measurements. Since snow is present at these two stations in 2014, it could bring interesting improvements in model results. At least, the authors should comment the impact of the choice of stations for the assimilation of snow depth data.

- A discussion part on the benefits and challenges of assimilation of snow data (both spatial and punctual) would be very valuable. It could include a discussion around the choice of the EnKF framework compared to the particle filter that has been recently used in several studies on data assimilation for snowpack model (Charrois et al. 2016, Magnusson et al. 2017). The fact that the EnKF required continuous values (and not binary values) should be mentioned in the paper. It illustrates a limitation of the EnKF for the assimilation of spatially distributed snow data. Ideally, the assimilation of snow cover would be done on a pixel to pixel basis as mentioned by the authors in their answer.

References:

Charrois, L., Cosme, E., Dumont, M., Lafaysse, M., Morin, S., Libois, Q., & Picard, G. (2016). On the assimilation of optical reflectances and snow depth observations into a detailed snowpack model. The Cryosphere, 10, 1021-1038.

Magnusson, J., A. Winstral, A. S. Stordal, R. Essery, and T. Jonas (2017), Improving physically based snow simulations by assimilating snow depths using the particle filter, Water Resour. Res., 53, 1125–1143, doi:10.1002/2016WR019092.

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ED: Publish subject to minor revisions (Editor review) (12 May 2017) by Guillaume Chambon

AR by Emmy Stigter on behalf of the Authors (18 May 2017) Author's response Manuscript

ED: Publish subject to technical corrections (02 Jun 2017) by Guillaume Chambon