Comments in the attachment.

OVERVIEW

The paper investigates the use of SMAR model to extrapolate CRNS soil moisture to deeper soil layers in a well-equipped site in Germany.

GENERAL COMMENTS

The paper is quite well written and clear, the topic is relevant to the SOIL readership, but I believe that some major changes are needed to make the paper more readable and scientifically sound. I have listed the general comments below, with an indication of their relevance.

• MAJOR: A large number of simulations have been carried out. It is difficult to make a summary of the results obtained and to clearly understand the more important scientific understanding that has been gained by carrying out the study. For example, when looking at the figures, it seems that no configuration gives satisfactory results, especially in terms of soil moisture dynamics. A RMSE lower than 0.06 cm^3/cm^3 is not very representative and depends on the dynamic range of the soil moisture data. I would strongly suggest reducing the number of simulations and focusing on more relevant results.

• MAJOR: Why are the results not as good as expected? Does it depend on the SMAR model, or on the CRNS data, or on the soil moisture benchmark? This should be clarified. For example, a simulation with surface and deeper layers from the Soil Moisture Benchmark data can give insight into the performance of SMAR. Some additional analysis in this direction should be done.

• MODERATE: Other methods have been proposed to extrapolate soil moisture data from the surface to deeper layers. The exponential filter is the most commonly used approach. I would suggest a comparison with such an approach, again to provide additional information on the performance of the SMAR model.

RECOMMENDATION

Based on the above comments, I suggest the paper needs a major revision before its potential publication.