A new map of permafrost distribution on the Tibetan Plateau

Zou, Defu; Zhao, Lin; Sheng, Yu; Chen, Ji; Hu, Guojie; Wu, Tonghua; Wu, Jichun; Xie, Changwei; Wu, Xiaodong; Pang, Qiangqiang; Wang, Wu; Du, Erji; Li, Wangping; Liu, Guangyue; Li, Jing; Qin, Yanhui; Qiao, Yongping; Wang, Zhiwei; Shi, Jianzong; Cheng, Guodong

doi:https://doi.org/10.5194/tc-11-2527-2017

Articles | Volume 11, issue 6

https://doi.org/10.5194/tc-11-2527-2017

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

https://doi.org/10.5194/tc-11-2527-2017

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

Articles | Volume 11, issue 6

Research article

|

08 Nov 2017

Research article |

| 08 Nov 2017

A new map of permafrost distribution on the Tibetan Plateau

Defu Zou, Lin Zhao, Yu Sheng, Ji Chen, Guojie Hu, Tonghua Wu, Jichun Wu, Changwei Xie, Xiaodong Wu, Qiangqiang Pang, Wu Wang, Erji Du, Wangping Li, Guangyue Liu, Jing Li, Yanhui Qin, Yongping Qiao, Zhiwei Wang, Jianzong Shi, and Guodong Cheng

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Final revised paper (published on 08 Nov 2017)
Supplement to the final revised paper
Preprint (discussion started on 20 Oct 2016)

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'Reviewer comments', Anonymous Referee #1, 04 Jan 2017
- AC1: 'Response to Referee #1', Defu Zou, 28 May 2017
RC2: 'Review of Zou et al', Anonymous Referee #2, 05 Jan 2017
RC3: 'Review of Zou et al - Revised for clarity', Anonymous Referee #2, 05 Jan 2017
- AC2: 'Response to Referee #2', Defu Zou, 28 May 2017

Peer-review completion

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

AR by Defu Zou on behalf of the Authors (08 Jun 2017) Author's response Manuscript

ED: Referee Nomination & Report Request started (27 Jun 2017) by Tobias Bolch

RR by Anonymous Referee #2 (10 Jul 2017)

RR by Anonymous Referee #1 (02 Aug 2017)

Suggestions for revision or reasons for rejection

I think the manuscript is much improved and makes an interesting and valuable contribution. However, I have three small points to consider before publishing. Apologies for extending the process but I think these are small issues that can be addressed easily.

1. I think it is important to differentiate between LST, which is a term that originates in the remote sensing community, eg. https://link.springer.com/referenceworkentry/10.1007%2F978-0-387-36699-9_79#CR866 and GST which is commonly used in the permafrost community. I know the authors are well aware of this differentiation and have published extensively on these topics as well as in their response to my original comment 1. I still do think it's important that the terms are applied consistently and rigorously in the manuscript to avoid confusion. For example in the Introduction at paragraph starting l.66 I feel like you should talk about GST observations, not LST. We typically measure GST on the ground, not LST (with exception of radiometers used for snow surface temp measurements, although these are calibrated for snow properties so the reading they give in absence of snow can be quite inaccurate) and in the original formulation of TTOP (Simth and Riseborough 1996) N factors are used to transfer air temperature to ground surface temperature NOT land surface temperature (what a satellite sees). N factors are used precisely to adjust for the effects of surface cover (veg/snow) which is not required for LST because LST measures the highest most layer ("skin-temp") of surface cover, whatever that happens to be at a given point in time. By definition, offsets generated by snow or vegetation layers are not relevant to LST.

You discuss this in your discussion but I think it would be much more useful to lay down the theoretical framework in your intro (as you do in part) and make sure LST and GST are well defined and not used interchangeably and any justification you have for using LST as GST is offered early on (probably best in Methods) so the reader is not left confused about what you do.

2. I still find structure missing in methods section particularly in terms of separating validation/driving data and the setup of the modelling scheme. I think a simple figure describing the modelling scheme would be a nice addition for the reader.

3. Gap filling has bias? As I understand HANTS (I'm using this source: https://mabouali.wordpress.com/projects/harmonic-analysis-of-time-series-hants/) it is a gap filling (among other functions) algorithm based on a kind of Fourier transform. My concern is that your MODIS LST obs are biased to clear sky conditions, being an optical sensor. Gap filling using such methods cannot recreate part of the data distribution that doesn't exist in the available dataset (i.e. cloudy sky conditions). Admittedly we talk about arid/semi-arid TP were clear-sky conditions dominate. I would argue that theoretically, this approach is not ideal and difficult to transfer to more humid regions, but practically it's possibly OK for your area. I think this issue should be discussed though.

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ED: Publish subject to minor revisions (Editor review) (16 Aug 2017) by Tobias Bolch

AR by Defu Zou on behalf of the Authors (25 Aug 2017) Author's response Manuscript

ED: Publish subject to minor revisions (Editor review) (15 Sep 2017) by Tobias Bolch

AR by Defu Zou on behalf of the Authors (25 Sep 2017) Author's response Manuscript

ED: Publish subject to technical corrections (04 Oct 2017) by Tobias Bolch

AR by Defu Zou on behalf of the Authors (05 Oct 2017) Author's response Manuscript

Short summary

The area and distribution of permafrost on the Tibetan Plateau are unclear and controversial. This paper generated a benchmark map based on the modified remote sensing products and validated it using ground-based data sets. Compared with two existing maps, the new map performed better and showed that permafrost covered areas of 1.06 × 106 km². The results provide more detailed information on the permafrost distribution and basic data for use in future research on the Tibetan Plateau permafrost.