Evaluating the E3SM land model version 0 (ELMv0) at a temperate forest site using flux and soil water measurements

Liang, Junyi; Wang, Gangsheng; Ricciuto, Daniel M.; Gu, Lianhong; Hanson, Paul J.; Wood, Jeffrey D.; Mayes, Melanie A.

doi:https://doi.org/10.5194/gmd-12-1601-2019

Articles | Volume 12, issue 4

https://doi.org/10.5194/gmd-12-1601-2019

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

https://doi.org/10.5194/gmd-12-1601-2019

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

Articles | Volume 12, issue 4

Model evaluation paper

|

24 Apr 2019

Model evaluation paper |

| 24 Apr 2019

Evaluating the E3SM land model version 0 (ELMv0) at a temperate forest site using flux and soil water measurements

Junyi Liang, Gangsheng Wang, Daniel M. Ricciuto, Lianhong Gu, Paul J. Hanson, Jeffrey D. Wood, and Melanie A. Mayes

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Final revised paper (published on 24 Apr 2019)
Supplement to the final revised paper
Preprint (discussion started on 05 Mar 2018)
Supplement to the preprint

Interactive discussion

Status: closed

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

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SC1: 'Executive Editor comment on "Evaluating the E3SM Land Model at a temperate forest site using flux and soil water measurements"', Astrid Kerkweg, 20 Mar 2018
RC1: 'Single point simulations using E3SM', Will Wieder, 03 Apr 2018
RC2: 'Comments on Liang et al. "Evaluating the E3SM Land Model ..."', Anonymous Referee #2, 13 Apr 2018
AC1: 'Response to all referees', Junyi Liang, 29 May 2018

Peer-review completion

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

AR by Junyi Liang on behalf of the Authors (15 Jun 2018) Author's response Manuscript

ED: Referee Nomination & Report Request started (08 Aug 2018) by Tomomichi Kato

RR by William Wieder (25 Aug 2018)

Suggestions for revision or reasons for rejection

Liang and co-authors have done a nice job revising their manuscript. At its core, this is a paper about soil moisture, productivity and respiration. This is a hard problem, and one which could be handled more thoughtfully in the discussion.

While I appreciate the qualifiers to text explaining to how “improving SWP directly improved soil respiration estimates” (top of page 8 & section 4.1), I would contend that the direct effects of SWP on respiration rates are overstated or unclear. It seems the improvements in soil respiration rates are driven by change in productivity (Fig. S1) which builds larger SOM pool. Specifically, it looks like at annual (Fig 2a, e.g. 2012) and seasonal (4c, shoulder seasons) scales the model shows a relatively low sensitivity to the modeled soil moisture scalar (xi_w). I think this is OK, E3SM is in good company (see Carvalhais et al 2014)!

The topic of soil moisture sensitivities is introduced again at the bottom of page 12 (section 4.2), but the discussion quickly moves onto temperature sensitivities and q10 before drifting off into soil microbes and fauna. As stated above, this is a paper about soil moisture, productivity and respiration. I’d argue ELM and other land models do fine with temperature, but really struggle with the soil moisture at seasonal and inter annual time scales. The changes to soil physics (the Hansen model) seem to improve dynamics of soil moisture stress, but without appropriate effects on the biogeochemistry. What modification could be made to the formulation of btran and xi_w? Are these functions that need new parameterizations, new forms, or that should be replaced in future generations of the model. I’m not asking for the simulations in the paper, but can these ideas be explored more in the discussion?

Towards this end, it’s still a little confusing what the most tractable way will be to parameterize soil hydrology in ELM. The authors discuss why the current approximation is sub-optimal (page 11-12), but can Hansen be applied in the global model? I'm assuming part of the motivation for this paper is to document the Hansen parameterization for work moving forward. If so, can the discussion more explicitly state how existing data can inform the global scale parameterization, application, and evaluation of the Hansen model? The current text seems somewhat vague.

It seems like ‘fixing’ a soil moisture bias in ELM exposed a compensating bias in the canopy photosynthesis (red lines in Fig. 4). I wonder if the proposed modifications to plant physiological parameters are also consistent with observations? Specifically, the add-hoc tuning (Table 2) of SLA (to reduce LAI) and FLRN (to modify Vcmax and maintain GPP with a less leafy canopy) certainly worked (Fig. 4). I wonder if the modifications are at all consistent with leaf physiology measurements from the site or from similar plants in the TRY database?

Minor and technical concerns:
In general, I'm not a fan of introducing new analyses / results at the end of the discussion (Fig. 5). As such, I’d encourage moving this display item into the results (section 3) and mentioning the experiment in the methods (section 2), but leave this up to the authors & editor to decide.

Why not put the uncertainty bands on both parts of Fig. S5 (and other bar charts in the manuscript)?

References:
Carvalhais, N., Forkel, M., Khomik, M., Bellarby, J., Jung, M., Migliavacca, M., et al. (2014). Global covariation of carbon turnover times with climate in terrestrial ecosystems. Nature, 514(7521), 213-217. doi: 10.1038/nature13731.

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RR by Anonymous Referee #3 (12 Oct 2018)

ED: Reconsider after major revisions (12 Oct 2018) by Tomomichi Kato

AR by Junyi Liang on behalf of the Authors (05 Dec 2018) Author's response Manuscript

ED: Referee Nomination & Report Request started (14 Jan 2019) by Tomomichi Kato

RR by Anonymous Referee #3 (05 Mar 2019)

ED: Publish subject to minor revisions (review by editor) (21 Mar 2019) by Tomomichi Kato

AR by Junyi Liang on behalf of the Authors (30 Mar 2019) Author's response Manuscript

ED: Publish as is (03 Apr 2019) by Tomomichi Kato

Short summary

Soil respiration, the second largest carbon fluxes between the atmosphere and land, is not well represented in global land models. In this study, using long-term observations at a temperate forest, we identified a solution for using better soil water potential simulations to improve predictions of soil respiration in the E3SM land model. In addition, parameter calibration further improved model performance.