Impacts of topographic shading on direct solar radiation for valley glaciers in complex topography

Olson, Matthew; Rupper, Summer

doi:https://doi.org/10.5194/tc-13-29-2019

Articles | Volume 13, issue 1

https://doi.org/10.5194/tc-13-29-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/tc-13-29-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 13, issue 1

Research article

|

08 Jan 2019

Research article |

| 08 Jan 2019

Impacts of topographic shading on direct solar radiation for valley glaciers in complex topography

Matthew Olson and Summer Rupper

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Final revised paper (published on 08 Jan 2019)
Preprint (discussion started on 13 Apr 2018)

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'Short Review', Geoff Evatt, 01 Jun 2018
RC2: 'Review', Anonymous Referee #2, 15 Jun 2018
AC1: 'Author's response to reviewer comments RC1 and RC2', Matthew Olson, 31 Aug 2018

Peer-review completion

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

AR by Matthew Olson on behalf of the Authors (31 Aug 2018) Author's response Manuscript

ED: Referee Nomination & Report Request started (26 Sep 2018) by Christian Haas

RR by Geoff Evatt (09 Oct 2018)

RR by Anonymous Referee #2 (09 Oct 2018)

Suggestions for revision or reasons for rejection

The authors have significantly improved the MS relative to the first version. The modelling section is easier to understand and justifications and explanations have been added. Although, as noted in the reviews of the first version, the paper does not really present a new insight it is a helpful reminder of the importance of topographic shading on a glacier surface. I accept the argument that the topography can be exceptionally complex in the Himalayas. There are a couple of things that I don't understand (and I should have noticed these in version 1). In fig 7, and the text describing it, I don't understand why a dependence on 1-tan(beta) would be expected, or how the dashed lines can represent such a variation if they both pass through zero when beta=1 (which they appear to do). Fig 10 presents the effect of DEM resolution on topographic shading, and suggests a logarithmic relationship. I don't really follow what is being proposed here. The equation 'f(x)=y~log(x)' is unclear. I guess it means either that ∆I = - a log(r) or -a log (r) + b (I being irradiance and r resolution), though whether a or b should be the same for the two glaciers of not is not discussed. The dotted lines in the graph are not explained, but perhaps least-squares fits to the model (although they appear to consist of straight-line segments rather than smooth logarithmic functions). But most puzzling, I don't know how to interpret the fact that these models will not work as the DEM resolution tends to zero.

Minor:
p1L7 'shading' is not a parameter (though it can be parameterised)
p1L14 'some predictable characteristics' - seems a misleading expression here: surely it is entirely predictable if topography is known?
P1L19 'thermal expansion' of oceans, presumably
p3L5 'he suggested' -> 'they suggested'
p4L3 'parse out' does not seem like a correct phrase here. I only know its meaning in the contexts of language and computer programming. Perhaps 'attribute'?
P5L26 'parse out' again
p7L25 'according to the best perceived aspect' - I don't know what this means.
p14L9 delete hyphens from on-the-other-hand
p16L20 a linear increase in MODELLED glacier melt?
p18L10 omit hyphen from 'most-shaded'
omit the dots from equations 3-6; don't indent the text immediately following an equation (unless a new paragraph)

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ED: Publish subject to minor revisions (review by editor) (30 Oct 2018) by Christian Haas

AR by Matthew Olson on behalf of the Authors (09 Nov 2018) Author's response Manuscript

ED: Publish as is (26 Nov 2018) by Christian Haas

AR by Matthew Olson on behalf of the Authors (05 Dec 2018) Manuscript

Short summary

Solar radiation is the largest energy input for most alpine glaciers. However, many models oversimplify the influence of topographic shading. Also, no systematic studies have explored the variable impact of shading on glacier ice. We find that shading can significantly impact modeled solar radiation, particularly at low elevations, at high latitudes, and for glaciers with a north/south orientation. Excluding the effects of shading will overestimate modeled solar radiation for alpine glaciers.