Interactive comment on “ A two-sided approach to estimate heat transfer processes within the active layer of rock glacier Murtèl-Corvatsch ”

Introduction Conclusions References

1. We agree with reviewer #1 that an additional parameter is likely to increase the modeled thermal regime substantially.However, the parameter is kept constant over the respective 4 month periods during all the calculations and it is integrated into a fully coupled heat and mass transfer model with freezing and thawing.Our experience C174 shows in general that the improvement of a model performance by simply adding more parameters does not automatically lead to better model results.
2. As reviewers #2 and #3 had no major objections concerning the usefulness of the modeling approach, the authors will keep the structure of the manuscript including the modeling part.Regarding the discussion of the benefit of the two approaches, the similarity of the order of magnitude of the calculated energy balance components within the active layer and the model parametrization (i.e. the heat source/sink) will be addressed more clearly in the revised version of the manuscript.
3. We agree with reviewer #1 and #3 that an assessment of the errors associated with all the parameters would be helpful to the reader, but to do this with justified ranges for both approaches would bebeyond the scope of the here presented manuscript (see e.g.Gubler et al., 2013, who addressed in a pure modeling study only this topic).Nevertheless, we pointed out in several paragraphs of the manuscript that the uncertainties of our approach are (probably) very large and that our results should be interpreted qualitatively.We will clarify this in the revised version at the respective places in the manuscript.
4. Grammar and typographical corrections as well as changed expressions as suggested by the referees will be used in the revised version of the manuscript.
5. Units will be given for all variables used in the revised version of the manuscript.Also, symbols will be used in a consistent way throughout the entire manuscript.

Anonymous Referee #2 General Comments
There are two main components to this paper.First, a detailed calculation of energy balance fluxes at a rock glacier in the Swiss Alps, based on an impressive multiyear series of micrometeorological measurements.Second, the simulation of energy fluxes and active layer temperatures at different depths using the COUP model.The main finding is that introducing a heat source/sink layer in the model to account for air flow driven heat transfer dramatically improves the fit to measured borehole temperatures.
The authors estimate freezing and thawing rates in the active layer and at the permafrost table from the residuals in the energy balance.These latter results must be treated with caution due to the simplifying assumptions applied in the methodology.While this is an interesting study, greater clarity is needed in the explanations of the energy flux calculations.Other than the model development, it isn't clear what new insights into active layer processes are gained since much of the consists of a general discussion of uncertainties in the two approaches which are not clearly quantified.I think the authors underplay their work and findings in this respect, and could improve this aspect of the paper in a revision.

Detailed comments
Equations 4-8 give the gradient form of the aerodynamic equations.It appears the bulk aerodynamic approach is applied, however, in which case surface values of temperature and humidity are needed, but it isn't clearly explained how these variables are measured.Both surface temperature and humidity are difficult to measure or model accurately and a quantification of the error range and its effect for both variables is really needed.There appears to be some confusion over symbols.The letter z is used for both height and 'surface roughness' (p 148, l22).I assume the latter is really the 'aerodynamic roughness', which should be defined as the standard symbol z_0, as this is required in bulk aerodynamic approach.What value of roughness was used and how was it calculated and estimated?
As the reviewer correctly points out, we used the bulk aerodynamic approach in our study.The value used for surface roughness was 0.07 m for snow covered conditions and 0.18 m for snow free conditions (Stocker-Mittaz, 2002).The letter z is used for 'log mean height', this will be detailed in the revised version of the manuscript.We agree with the reviewer that assuming a saturated surface will lead to errors.As measurement conditions at the heterogeneous surface of the rock glacier with moist conditions in C176 the depressions and dry conditions at the top are difficult we consider that assuming saturated conditions is a reasonable approximation.Eddy covariance measurements, which are not yet available at the study site, would certainly improve the calculations.This will be clarified in the respective paragraphs in the methods and the discussion section of the revised manuscript.

154, 6
The parameterization of the heat source/sink layer isn't clear.Explain what the form of the parameterization is and how it was implemented in the model.What are the 'values' that were 'adjusted experimentally'?What was the range of variation of these values and do they have any physical meaning or are they purely empirical?
Parameterization of the source/sink layer consists of a constant value [W/m2] which is either added to, or extracted from the system.The parameter changes in 4 month periods.It is positive in summer, negative in fall/winter and zero in spring.To find the right range, the parameters were chosen based on previous studies by Stocker-Mittaz (2002) and adjusted iteratively until the modeled temperatures matched the observed temperatures.The physical meaning is complex and might be (partly) explained by processes occurring in nature that are not represented in the model, e.g.radiative heat transfer within the active layer and turbulent fluxes in the macropores.This will be clarified in the revised version of the manuscript.
150, 1-3, this sentence doesn't make sense to me, please clarify We agree that this sentence is unclear and we will clarify the explanation in the revised version of the manuscript: The threshold temperature for snow melt is set to -3 • C, below this temperature no snow melt is calculated even if a decrease in snow height is measured.In addition, a measurement error is expected if the snow height decreases by more than 0.2 m in a 24 h interval.In this case, no snow melt is calculated.
150, 14, the correction factor needs justifying We thank the reviewer for this comment as this was clearly a mistake in the calculation