the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 26 May 2026
Development and evaluation of the ECHAM6-iMAPLE v1.0 coupled atmosphere-ecosystem model
Abstract. Land-atmosphere interactions play a fundamental role in regulating climate variability, ecosystem productivity, and air quality through coupled exchanges of energy, water, carbon, and reactive trace gases. However, many Earth system models adopt simplified representations of vegetation physiological processes, leading to biases in terrestrial carbon and water fluxes and increased uncertainties in climate simulations. Here, we present ECHAM6-iMAPLE v1.0, a newly coupled modeling framework that integrates the interactive Model for Air Pollution and Land Ecosystems (iMAPLE v1.0) into the ECHAM6 atmospheric general circulation model. The coupled model is evaluated against reanalysis, benchmark, and satellite datasets. Compared with the original configuration, ECHAM6-iMAPLE substantially improves simulations of gross primary productivity, evapotranspiration, and leaf area index, capturing their spatial distributions and seasonal cycles more reasonably. These improvements arise from well-constrained physiological parameters calibrated using extensive site-level observations and a more realistic representation of key biophysical processes in iMAPLE. With improved carbon and water fluxes, simulations of soil temperature, soil moisture, and surface air temperature show reduced root mean square errors. Overall, evaluations demonstrate that ECHAM6-iMAPLE provides a useful tool for investigating atmosphere-ecosystem interactions and their implications for future climate change projections.
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Status: final response (author comments only)
- RC1: 'Comment on egusphere-2026-1884', Anonymous Referee #1, 29 Jun 2026
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RC2: 'Comment on egusphere-2026-1884', Anonymous Referee #2, 27 Jul 2026
Review for Development and evaluation of the ECHAM6-iMAPLE v1.0 coupled atmosphere-ecosystem model
In their manuscript “Development and evaluation of the ECHAM6-iMAPLE v1.0 coupled atmosphere-ecosystem model”, the authors describe and present some benchmarking analysis of the ECHAM6 atmospheric model coupled to the iMAPLE v1.0 land model, in place of the JSBACH land model.
The manuscript is overall well written, and the benchmarking analysis is fairly clear. Following minor revisions, this study would be suitable for publication in the EGU family of journals.
My largest point of confusion was that it was unclear until fairly late in the manuscript if iMAPLE was being imposed alongside JSBACH to handle certain specific aspects of the land surface, or if JSBACH was being entirely removed and replaced by iMAPLE. Specific comments are listed line by line below.
Line 108 – surely JSBACH was already doing this, was it not? (a process-based simulation of soil temperature and moisture, even if it was different than the approach used by NOAH-MP)
Section 2.1 – clearly delineating what JSBACH did not do that required replacement with iMAPLE would be valuable. Or, if it is just a different approach to the land model (but covering the same processes as JSBACH), that is still valuable – the entire premiss of CMIP is “have more models/model combos” – but make it clear that that is the case.
Section 2.1 – clearly delineating what the difference between NOAH-MP and iMAPLE is --- does iMAPLE add layers of complexity to NOAH-MP, or does it use parts of NOAH-MP’s code (eg solving the soil energy budget) and not other parts?
Line 183-185: was not clear here if ECHAM (JSBACH) or MAPLE is handling the land. Which component of the model is responsible for what? Does MAPLE just do the vegetation, or all land surface properties? How does that interact with the physical surface like feedbacks between leaf area and albedo?
Line 197-198: not clear if iMAPLE is replace JSBACH, or replacing only parts of it, OR only adding new functionality, and stuff that iMAPLE did that JSBACH was already doing doesn't get incorporated and the JSBACH processes are used.
Line 271-274: implies JSBACH is entirely removed/bypassed. Is that correct?
Figure 1 / related text: no discussion about representation of aerodynamic properties or turbulence - are they static, time evolving, using Monin Obukhov similarlity theory/something else?
Figure 1: What component of the model is dealing with the entire centre column?
Figure 5: Is this full column soil moisture, or near surface, or root zone, or something else? How does each model handle ground water (if at all – and is it included in this figure?)
Figure 6 (and also figure 5, but especially true in 6): this is quite hard to compare. Perhaps show MERRA-2, then the difference of iMAPLE-MERRA or JSBACH-MERRA in the middle and right columns?
Citation: https://doi.org/10.5194/egusphere-2026-1884-RC2
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This manuscript presents and evaluates a new model framework that integrates the widely used ECHAM6 atmospheric general circulation model with the dynamic vegetation model iMAPLE. The evaluation compares simulated carbon and water fluxes and other variables such as soil temperature and moisture against observational benchmarks as well as against the ECHAM6 model coupled with the land surface model JSBACH.
While the manuscript itself is well presented and the figures are overall of good quality, I would argue that the manuscript requires substantial revision and restructuring before it can be published. The following main points would need to be addressed:
1) As noted by the authors, both JSBACH and iMAPLE have already been extensively evaluated within the Global Carbon Budget (GCB) framework (the latest version being Friedlingstein et al. 2026, Figure S11), with results also publicly available online. The GCB2025 effort evaluates the same variables, using mostly the same benchmarks and evaluation metrics. It is thus unclear what gap this study fills other than repeating this analysis (at least for carbon and water fluxes as well as LAI). The key difference is that both models here were coupled to ECHAM6, whereas GCB2025 evaluates the model ‘offline’ (i.e. using a common, prescribed forcing). The manuscript should therefore clearly articulate what coupling to the atmosphere changes and what additional insight is gained. I recommend restructuring the paper to focus more explicitly on coupling effects, as partially illustrated in Figures 5 and 6.
2) Related to this, the Methods section needs to better reflect the Results. It is unclear why the Methods description focuses on photosynthesis even though this is the same as in the offline models, which have already been evaluated. The Methods should focus more on the coupling aspect of the model, i.e. addressing the question of how land-atmosphere feedbacks differ between the models and what effects this has on soil moisture, temperature, and other variables.
3) Paper framing: in addition to the points above, both the abstract and the introduction would need to make clear that this manuscript is not just about an evaluation of ECHAM6-iMAPLE but also, in large parts, a comparison with ECHAM6-JSBACH. It is a bit surprising that JSBACH is mentioned fairly late in the manuscript (section 2.1.2).
4) Benchmark datasets, particularly MERRA-2, need to be described in more detail. For example, how is soil moisture calculated in MERRA-2 and what assumptions are made? In addition, details on the simulation setup is required to ensure reproducibility of the analysis.
References:
Friedlingstein et al. (2026) Global Carbon Budget 2025, Earth Syst. Sci. Data, 18, 3211–3288, https://doi.org/10.5194/essd-18-3211-2026.