On the Predictability of Radiation Fog Formation in a Mesoscale Model: A Case Study in Heterogeneous Terrain
Round 1
Reviewer 1 Report
See the attached pdf
Comments for author File: 
Comments.pdf
Author Response
Major remark 1 :
I agree that it could be desapointing. However, the initial time of M50m models are chosen in order to explore at best the formation phase of fog. Given the fog formation time for the three area, the initial time are not the same for the three M50m models, but the simulation time cover the formation phase of the fog layer for the three studied areas. Sentences have been added to make this point clearer
Major remark 2 :
I agree that one cannot conclude that the difference between M50m and M500m are only a consequence of the horizontal resolution. The turbulent parameterization are chosen following previous work with meso-NH, and the turbulent parameterization depends on the horizontal resolution. Sentences have been added to clarify this point. Moreover, simulation at 500m resolution with the 3D turbulent shows similar results than simulation with BL89 turbulent scheme. However, this comparison is out of the goal of this article.
Major remark 3 :
I agree. An ensemble prediction system seems to be necessary to improve the fog prediction, and particularly during the formation phase. Sentences have been added to clarify this point.
Major remark 4:
I agree. Sentences have been added to the conclusion to make this point clearer.
Small Remarks 1-7 : done
Small Remark 8 : reference to IOP12 of LANFEX has been added
Small Remarks 9-12 : figures have been modified
Small Remarks 13-14 : time where the trajectory starts and ends have been added in blue in Figure 10. The results is not sensitive to the time frame as long as one focusses on formation phase of fog
Reviewer 2 Report
This paper presented an interesting study on fog over complex terrain with observations and numerical simulations at 500m and 50m grid spacings. The article is generally well written. However, several significant concerns need to be addressed before it can be accepted for publication.
Major points:
1) This paper is about the fog prediction, however, throughout the article, there is no visibility algorithm was used to predict the fog/visibility. Unfortunately, this is a significant defect.
2) The propose pseudo process diagram is not well described. It is very confused about how it was done.
3) Ensemble forecasts are needed to achieve the pseudo-process diagram. However, throughout the paper, only two sets of simulations (M500m, M50m) were performed. It is very puzzled what ensemble forecasts were used or how they are generated.
4) Many literature and previous studies from Northern America (e.g., many papers by Ismail Gullet and I. Gultepe et al., recent articles by Pu et al. -) were missing in the references.
Other points:
1) Line 39: Why are microphysics (nucleation process etc.) not the process that lead fog to form?
2)Line 41: "these physical processes" ... Could you specify?
3) Lin 142, Line144, Line 146; "30 October 2015" should be "31 October 2015".
4) Line 356: "Another other". need to revise
5) There are some typos in the paper text need to be taken care of. I will not list them here. Please read through carefully and correct them all.
Author Response
Major point 1 :
The key objective of this article is to better understand the apparently chaotic transition between the formation phase and the mature phase of fog.
By better understanding this transition, one can hope to better understand the physical processes driven the fog life cycle.
However, the key objectives of this work is not to improve our knowledge on the physical processes.
In the same way, the visibility calculation (e.g., Gultepe el al., 2006) is out of the goal of this article.
Sentences have been added in the revised version to clarify this point
Major point 2 :
The process diagram is a relatively new concept to explore model uncertainties.
The main goal is to highlight the dominant processes generating forecast spread by plotting the model prediction in model phase space and not in physical space. This concept has been previously used by Bosveld et al. 2014 (BLM) and Steeneveld and De Bode 2018 (QJRMS). It could be pretty confusing at the first time, but this study (and the previous studies) demonstrate that it is a very efficient tool for exploring the fog life cycle
Sentences have been added to clarify this point. We hope that it is now clearer.
Major point 3 :
Unfortunately, it is not currently possible to have at 50-m resolution ensemble forecast.
To overcome this problem, the members have been defined as the forecast at different grid points.
These ensemble forecast members could be seen as forecast members with different surface and atmosphere conditions but with the same physical processes given by the model, which is considered as perfect.
Sentences have been added in the revised version to clarify this point
Major point 4 :
Reference to MATERHORN project has been added in the introduction. A reference to the work on visibility parameterization by Gultepe et al. has also be added in the introduction.
We hope that it summarized the previous studies from Northern America. If you think that another important article is missing, do not hesitate to tell us, we will add it to the references.
Other point 1 : Microphysics is driven by the fog dynamics : if saturation is not reached (i.e. the cooling is too weak), fog will not form. This study focusses on fog dynamics. The impact of microphysics could be also very important, as said in introduction. However, it is out of the goal of this article.
Other point 2 : "these" has been deleted
Other point 3 : corrected
Other point 4 : corrected
Other point 5 : many typos has been corrected following the remarks of reviewers
Reviewer 3 Report
Please consult the uploaded pdf file.
Comments for author File: Comments.pdf
Author Response
The suggested modifications have been done in the revised manuscript. We want to thank the reviewer for his help in correcting many typos in the original manuscript.
