The Cycle 46 Configuration of the HARMONIE-AROME Forecast Model

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

It is ready for publication, congratulations.

Author Response

Thank you for your review. We received comments from the other two reviewers and the paper has been improved substantially based on these. 

Reviewer 2 Report

Comments and Suggestions for Authors

I was pretty much excited to read an updated description of an European consortium weather forecast model, HARMONIE-AROME.  Thus, I agreed to review this manuscript. My excitement continued through the abstract until the end of the first paragraph. However, the text is gotten muddled at a middle of the second paragraph, and this problem persists throughout the remainder of the manuscript.

Although the manuscript clearly contains valuable pieces of information, it is hardly a smooth reading.  Substantial edit and re-structuring of the text would be required for making this manuscript to be useful for the general audience.

As it stands for now, it is essentially  a straight collection of the documents provided by the consortium members. The text tends to fail to provide the readers an overview. Thus, it serves well only as an internal document of the Consortium.

For comparison, I looked at Bentgsson et al written for a previous cycle. I would think a good idea for the authors to take a similar structure as this published paper for this manuscript. Especially, for a better readability, I personally think it better to re-organize this manuscript to the order of Secs. 4, 2, and 3, than currently stands.

Moreover, it would be much helpful to provide an overview of the modifications from the previous cycle (CY40) to the present one (CY46): i.e., what has been problems with the cycle 40, and how those problems have been addressed in the cycle 46? As it stands for now, the modifications over those cycles are presented without those backgrounds, and it reads like just various random modifications have been made, say, based on the "personal" interests of individual researchers.

Same wise, it would be much desirable to present overall improvements of the forecasts over those cycles, by taking a benchmark case, thus the readers can get a better overall picture.  As it stands for now, each subsection presents certain particular aspects of the improvements of the model. However, it is hardly clear how those specific improvements are reflected upon overall improvements of the forecasts.

The following specific comments are highly selective, and only intended to serve as examples to more specifically demonstrating those general issues remarked.

*

Specific Comments:

L23-40: here the text suddenly turns to a particular technical issues without introducing any backgrounds motivate us to read those particularities of the model.  As a whole, the most readers would not be interested to know how a model script is written, unless it is crucial to understand the whole model structure as well.  Most importantly, I do not see any point of suddenly discuss about such a technicality at a middle of the introduction, when a more general background is still to be properly introduced.

L24, the so-called HARMONIE scripting system: is it a particular jargon that has been used in the HARMONIE community? Or is it a standard terminology used among the IT people? Being either the case, for me, this term sounds like an AI that can write a drama script automatically. As I suspect, a "script file", is what they want to mean here.

L29, the scripting system facilitates.....: I'm not sure whether the choice of the word "to facilitate" is optimal here.  Practical speaking, a certain script file is an inevitable necessity to put all the components of the codes of a model together, although an alternative may exist in theory.

This is just an example that the authors often choose odd wordings, when the same can be said more lucidly with different words.

L38-40: The same as the previous paragraph, I do not see a reason to suddenly introduce an availability of a single-column version, when a more general overview of the model is still to be introduced.

L41-: this lead sentence of the paragraph is by itself fine. However, it should be followed by a sentence of explaining why a presentation of the cycle 46 is necessary, if it is not done with the cycle 45, and without waiting for the cycle 47 to be ready. The readers would like to know a general motivation to publicize about the cycle 46.

L43, we have limited the discussions to.....: for me, this is a very odd remark. The readers would rather like to read a more general description of how the HARMONI-AROME has been modified over those six cycles, and what are the main improvements, etc.  Such a limited presentation would only be meaningful as an internal document designed for those people already familiar with all the details of the models as well as all the other modifications documented or to be documented in the other internal materials.

This is where we need a more overview of the basic model configuration. Oddly enough, the text even fails to describe the basic nature of HARMONI-AROME: most notably,  is it a global model or else?

2.1 Radiation, L52: the most readers would be simply shocked to suddenly read a very particularly specified phrase "The Moncriette radiation scheme from ECMWF....", when nothing general about HARMONIE-AROME is yet to be presented.

L68-: I do understand an importance of introducing more diverse types of the aerosols to the radiation scheme.  However, I should also point out that it would be only one of the many aspects to be improved with the radiation: how this priority is chosen, or what motivated the HIRLAM community to investigate heavily towards this direction?

This is only a first example of what is found in many other model modifications: please introduce a clear motivation behind for given modifications.

In what follows, the authors present the three developments with the radiation that were made. Here, I would like to read how these three developments are interrelated. For example, the second development follows from the first?

L120-121:  this is a rare occasion that the authors introduce a motivation for a modification, however in a backward manner: we introduce a modification to remove an existing problem. Here, it sounds like they only find an improvement only as an "after-fact", incidentally.

L125, the remainder of this section is dedicated to......: what is the purpose of a phrase sounds like a special "fanfare" to introduce the third development: is there any particular importance?  Do we need a "special" space "dedicated" to describe this particular modification?  If not, this introductory phrase does not make any sense.

Sec. 2.2 Convection, L158-160:
this lead sentence makes us think that this subsection is to going to describe the three boundary layer processes: clouds, turbulence, and cumulus convection. However, the subsection title suggests otherwise, and it appears that the latter is actually the case.

L160-162: this general remark is what we need to read in the introduction.

L164-165: this must be the lead sentence of this subsection.

However, here and elsewhere, the authors adopt a strange use of the verb "to focus":  when we say we focus on something, there must be a more general theme for a given subsection, and the verb "to focus" should suggest that under this general theme, the authors specify a "focus" of a presentation. Of course, this is merely a "focus", we expect to read some other remarks on a given more general subject.

Here, simply, this subsection "presents" changes with convection (and nothing else).

Another examples of an odd use of the word "to focus" are found in e.g., L191-192.

L157-165: I consider this paragraph as a whole a good example of a bad writing style of the present manuscript as a whole.

L632-633: this kind of the presentations on the general configuration of HARMONIE-AROME is what the readers would like to read before the technical details of the radiation, etc. This would be the enough reason to put Sec. 4 before Sec. 2.

L666-667, CY46 and CY49: why and how the developments jump from CY46 to CY49? A detail that only the insiders would know, but the general readers would have no crew what the matters with CY49, rather than CY47.

L671, severely outdated: this is a very informal discourse style. One needs a more specific motivation to replace a given scheme.

L674, modern gas optics schemes: is it a technical term or does it just mean "more recently developed gas optics schemes"? Either the case, some elaborations as well as references are required.

Sec. 5.2 title: to be changed to "scale aware shallow convection and turbulence", because this section covers both.

L713-714: These two sentences are hard follow, and also unclear how these two separate remarks about the two different subjects (boundary layer and convection) must be stated in sequence. Is there any general theme behind, or we are just reading two random remarks?  Please note that neither remark makes any sense without substantial expert knowledge.

L735, aerosol population: "aerosol distribution" could be clearer. However, do they also want to mean different categories of aerosols? I personally see a use of the term "aerosol" in the context of the microphysics could be misleading, because not all the aerosols are active as condensations nuclei, especially for the ice. Only the latter category of aerosol counts in the cloud microphysics.

Sec. 5.5: in spite of the heading of this section, it actually begins by a general remark about the difficulties of progressing towards a fully convective resolving numerical weather forecasts. Extensive expected issues are rather thoroughly discussed in Yano et al. (2018 BAMS).  I should emphasize that this essay was written with extensive contributions of the HIRLAM-ALADIN community (as well as COSMO). Unfortunately, this section narrowly reduces the issues to the numerical algorithms for the dynamic core, and more specifically of the time integration scheme.  A good reminder of the general issues, or at least a reference to this essay would be warranted.

End: I was surprised to read no conclusion in the manuscript. A short paragraph of wrap up would be helpful.

References:

2. Provide a web link and/or the issue number for this technical report

32. "M'et'eo France" should be read "Météo France" or "M\'et\'eo France" in TeX

101. Please update this reference. Has it been published or accepted? I could not find it on QJ web site.

Comments on the Quality of English Language

see the general comments above

Author Response

I was pretty much excited to read an updated description of an European consortium weather forecast model, HARMONIE-AROME.  Thus, I agreed to review this manuscript. 

Thank you for kindly reviewing our paper. We really appreciate your comments and have worked on these to improve the Technical Report.

My excitement continued through the abstract until the end of the first paragraph. However, the text is gotten muddled at a middle of the second paragraph, and this problem persists throughout the remainder of the manuscript. 

Although the manuscript clearly contains valuable pieces of information, it is hardly a smooth reading.  Substantial edit and re-structuring of the text would be required for making this manuscript to be useful for the general audience.

We have made substantial changes to the structure of the paper, including clearer descriptions and missing definitions and information.

As it stands for now, it is essentially  a straight collection of the documents provided by the consortium members. The text tends to fail to provide the readers an overview. Thus, it serves well only as an internal document of the Consortium.

Yes we agree and have edited it heavily to improve the flow and continuity.

For comparison, I looked at Bentgsson et al written for a previous cycle. I would think a good idea for the authors to take a similar structure as this published paper for this manuscript. Especially, for a better readability, I personally think it better to re-organize this manuscript to the order of Secs. 4, 2, and 3, than currently stands. 

We have changed the section order and the names of some of the sections and subsections to make it clearer.

Moreover, it would be much helpful to provide an overview of the modifications from the previous cycle (CY40) to the present one (CY46): i.e., what has been problems with the cycle 40, and how those problems have been addressed in the cycle 46? As it stands for now, the modifications over those cycles are presented without those backgrounds, and it reads like just various random modifications have been made, say, based on the "personal" interests of individual researchers. 

NWP systems do not develop linearly, so that each new version addresses issues found in the previous version. Coping with known issues is only one of the reasons for new implementations. In such a big system as an NWP model, the motivation for particular studies and implementations can be very different. For example, developments can be devoted to the representation of physical processes, which are known to be missing in the model and believed to be important. There are developments aimed at implementing better physically-based methods and algorithms, or new databases. Sometimes we improve the consistency between different parts of the model. There are also tuning efforts. Tens of people participated in the HARMONIE-AROME model developments during the 7-year period. This paper has more than 30 co-authors. It is impossible to describe each study in the overview according to some standard scheme, which would include detailed motivations. We therefore only provide an outline of improvements, with some essential features and illustrations, and refer the reader to publications on particular developments. 

“In this manuscript an overview of developments of the HARMONIE-AROME canonical system configuration of the ACCORD NWP system between Cycles 40 and 46 is presented. Information on innovations that happened during this lengthy period of time may be of interest to NWP developers from other consortia, forecasters and academic researchers. Tens of people participated in the model developments. Contributions varied a lot in size and in impact, from small implementations (or even bug corrections, yet having a meteorological impact) to the application of new schemes. Due to that, it is impossible to give all of the details. We only provided an outline of improvements, with some essential features and illustrations, and refer the reader to publications about particular developments.”

We also provide a description of different kinds of motivation in the manuscript:

“In such a big system as an NWP model, the motivation for particular studies and implementations can be very different. Some developments aim to address well-known model issues like the integral revision of the Convection, Turbulence and Cloud scheme that improved several aspects of the model, but was especially aimed at providing a better representation of low clouds (Section 3.3). Other examples to address important model deficiencies are the calculations of the LW emissivity in Section 3.1 and attempts to improve simulations in stable boundary layer conditions described in Section 4.4. Some developments are devoted to the representation of physical processes, which were missing in the model and believed to be important. In this overview, examples of such studies are the use of NRT aerosols (Section 3.1 and Section 3.2.2) and the implementation of the lake model, FLake (Section 4.7). There are also developments that deal with the implementation of recent knowledge, such as improved physically based methods and algorithms, or new databases. Examples of such are the implementation of the Wind Farm Parameterisation (Section 3.3.4) and the new physiography land cover map ECOSG (Section 4.1). Also, there were many efforts to improve the consistency between different parts of the model, as well as tuning work. The radiation and microphysics schemes were made more consistent through the use of a common cloud droplet number concentration. An example of tuning is the option to include additional 10~m trees to increase the roughness length over low vegetation while using the ECOSG land cover map (Section 4.1).”

We also include information on the model cycles and how they are connected:

“ACCORD shares some developments (parts of the code) with the European Center for Medium-Range Weather Forecasts (ECMWF) Integrated Forecasting System (IFS) model. This is possible due to the modularity of the code. To ensure consistency of the common code, ACCORD follows the releases of the IFS, known as cycles. When a new IFS cycle is issued, parts of the HARMONIE-AROME code are adjusted to collocate with it, and new developments are merged in. The basic cycle numbers for HARMONIE–AROME follow the IFS cycle numbering. Local developments of HARMONIE–AROME, starting from the basic IFS release, can lead to additional local releases. Because the process of merging and harmonisation is time-consuming, some IFS cycles are skipped. In this paper, we present the latest release of the HARMONIE-AROME Reference system, which is Cycle 46. Previous HARMONIE-AROME releases were based on Cycle 43. The release described in Bengtsson et al. was related to Cycle 40 and the next release will be Cycle 49.”

We have included improved descriptions in the overview and explanations why the changes were made, where possible. 

Same wise, it would be much desirable to present overall improvements of the forecasts over those cycles, by taking a benchmark case, thus the readers can get a better overall picture.  As it stands for now, each subsection presents certain particular aspects of the improvements of the model. However, it is hardly clear how those specific improvements are reflected upon overall improvements of the forecasts.

The process to accept suggested changes into an NWP model is quite complicated. First, the developer makes his/her own evaluation of the implementation, based on specially designed experiments, and possibly additional observations. Results of these evaluations are shown in the paper. Then, suggestions from different researchers for a certain time period are collected together. They are merged with the new ECMWF cycle if needed. As a result, a model release candidate appears. Then, this release candidate is tested by different national weather centres, and their groupings, over different model domains and different seasons, with reference to the previous release version. All results are evaluated carefully, with different types of scores, score maps for different variables, etc. If necessary, case studies are also involved. So, this is not simply evaluation against some benchmark case, the process is much more complicated. We include examples of model evaluation of HARMONIE-AROME Cycle 46 against Cycle 40 in the Conclusion section. 

The following specific comments are highly selective, and only intended to serve as examples to more specifically demonstrating those general issues remarked.

Specific Comments:

L23-40: here the text suddenly turns to a particular technical issues without introducing any backgrounds motivate us to read those particularities of the model.  As a whole, the most readers would not be interested to know how a model script is written, unless it is crucial to understand the whole model structure as well.  Most importantly, I do not see any point of suddenly discuss about such a technicality at a middle of the introduction, when a more general background is still to be properly introduced.

We agree that technical details should not appear in the Introduction. However we think that the system infrastructure is an important component of the NWP system, because it is an environment for common developments and for cooperation. We have moved the brief description of the system infrastructure to the “Dynamics, Model Configuration and System aspects” section. We explain why the system infrastructure is important:

“System Aspects usually don't get much attention in scientific publications. In the area of NWP, however, we think that these are important. A common working environment facilitated by the model infrastructure, enables effective exchange of knowledge in a large community, and results in easier application of the code to operational weather forecasting. This infrastructure is built and maintained by the HIRLAM community .”

We have included a figure that shows the components of the HARMONIE-AROME NWP system infrastructure to make it clearer. We have made the Introduction section clearer. 

L24, the so-called HARMONIE scripting system: is it a particular jargon that has been used in the HARMONIE community? Or is it a standard terminology used among the IT people? Being either the case, for me, this term sounds like an AI that can write a drama script automatically. As I suspect, a "script file", is what they want to mean here.

“Scripting system” means the system of scripts written in bash, Python, etc. to run the model in different modes (research or operational). “Scripting system” is a widely used term in the community of NWP developers. HARMONIE is the name of this scripting system. A better description is added:

“Within ACCORD only the FORTRAN code of the CSCs is shared, but the infrastructure to run the model in research or operational mode is not. To run the HARMONIE-AROME CSC, both for research and operations, a HARMONIE-specific software infrastructure is used. The main part of this is the so-called Harmonie scripting system, written in several system scripting languages, Python, perl, etc. The scripting system organises the data flow for all parts of the system, including the generation of external parameters, the management and quality control of the observations, variational data assimilation, the preparation of boundary conditions, running the forecast, post-processing and the extraction of data for model verification. The model can run in ensemble mode, and this possibility is also provided by the scripting system. A work-flow manager called ecFlow, developed by ECMWF, is also part of the HARMONIE software infrastructure.”

L29, the scripting system facilitates.....: I'm not sure whether the choice of the word "to facilitate" is optimal here.  Practical speaking, a certain script file is an inevitable necessity to put all the components of the codes of a model together, although an alternative may exist in theory.

This is just an example that the authors often choose odd wordings, when the same can be said more lucidly with different words.

We changed the wording, added explanations, moved the text into the section “Dynamics, Model Configuration and System aspects” and stressed the importance in Conclusions. Details are provided in the answers to previous comments. Note that the scripting system is not just one central script. It is really a system, containing hundreds of scripts, hundreds of lines each.

L38-40: The same as the previous paragraph, I do not see a reason to suddenly introduce an availability of a single-column version, when a more general overview of the model is still to be introduced.

The description of the single-column version of the model is moved to the section on “Dynamics, Model Configuration and System aspects”. We would like to mention the single-column version of the model called MUSC because we used it for some of the studies presented in the manuscript.

L41-: this lead sentence of the paragraph is by itself fine. However, it should be followed by a sentence of explaining why a presentation of the cycle 46 is necessary, if it is not done with the cycle 45, and without waiting for the cycle 47 to be ready. The readers would like to know a general motivation to publicize about the cycle 46.

We have now added the explanation into the Introduction: 

“ACCORD shares some developments (parts of the code) with the European Center for Medium-Range Weather Forecasts (ECMWF) Integrated Forecasting System (IFS) model. This is possible due to the modularity of the code. To ensure consistency of the common code, ACCORD follows the releases of the IFS, known as cycles. When a new IFS cycle is issued, parts of the HARMONIE-AROME code are adjusted to collocate with it, and new developments are merged in. The basic cycle numbers for HARMONIE–AROME follow the IFS cycle numbering. Local developments of HARMONIE–AROME, starting from the basic IFS release, can lead to additional local releases. Because the process of merging and harmonisation is time-consuming, some IFS cycles are skipped. In this paper, we present the latest release of the HARMONIE-AROME Reference system, which is Cycle 46. Previous HARMONIE-AROME releases were based on Cycle 43. The release described in Bengtsson et al. was related to Cycle 40 and the next release will be Cycle 49.” 

L43, we have limited the discussions to.....: for me, this is a very odd remark. The readers would rather like to read a more general description of how the HARMONI-AROME has been modified over those six cycles, and what are the main improvements, etc.  Such a limited presentation would only be meaningful as an internal document designed for those people already familiar with all the details of the models as well as all the other modifications documented or to be documented in the other internal materials.

This was wrong wording from our side, which resulted in a misunderstanding. We were only going to say that the DA part is not included in the manuscript. Otherwise, the paper contains all of the material, which you would like to see in the paper. Now the wording has been changed to: 

“The DA system and ensemble system are not covered in this paper.”

This is where we need a more overview of the basic model configuration. Oddly enough, the text even fails to describe the basic nature of HARMONI-AROME: most notably,  is it a global model or else?

We have updated the intro to include this information:

“HARMONIE–AROME is a limited-area, mesoscale, spectral, nonhydrostatic model. It features a dynamical core developed within the ALADIN consortium (Bubnová et al., Benard et al.}. However, several adaptations and improvements were made to the model by scientists from the HIRLAM countries, mainly to the atmospheric and surface physical parametrizations. The model incorporates parameterizations for shortwave and longwave radiation, land-surface processes, cloud dynamics and microphysics, turbulence and shallow convection. With a grid spacing of 2.5~km, the model is designed to resolve and explicitly simulate deep convection through its nonhydrostatic dynamics, eliminating the need for a deep convection parameterization.”

2.1 Radiation, L52: the most readers would be simply shocked to suddenly read a very particularly specified phrase "The Moncriette radiation scheme from ECMWF....", when nothing general about HARMONIE-AROME is yet to be presented.

Now general information is included in the Introduction section. In particular, in relation to ECMWF:

“ACCORD shares some developments (parts of the code) with the European Center for Medium-Range Weather Forecasts (ECMWF) Integrated Forecasting System (IFS) model. This is possible due to the modularity of the code.”

L68-: I do understand an importance of introducing more diverse types of the aerosols to the radiation scheme.  However, I should also point out that it would be only one of the many aspects to be improved with the radiation: how this priority is chosen, or what motivated the HIRLAM community to investigate heavily towards this direction?

We have added the following to the radiation section:

“Clouds and aerosols cause the biggest current uncertainties in both SW and LW radiative fluxes in atmospheric models. In particular, the effect of aerosols on clouds is generally recognized (Forster et al.) as the biggest radiative forcing uncertainty.”

In addition to that, we added explanations about motivations for NWP developments in general, with the NRT aerosol scheme among the examples:  

“Some developments are devoted to the representation of physical processes, which were missing in the model and believed to be important. In this overview, examples of such studies are the use of NRT aerosols (Section 3.1 and Section 3.2.2) and the implementation of the lake model, FLake (Section 4.7).”

Also, the NRT scheme contains not only the representation of aerosols as such, but also improved algorithms for radiation and microphysics. Therefore, this implementation is the first step towards better understanding the role of aerosols and the impact of different processes in radiation and microphysics. The following was added to explain the motivation and to describe the status of this development:

“A significant contribution during the past few years was the development of a method for coupling and use of external prognostic aerosol data in a limited-area high-resolution NWP model, in particular in its microphysics parametrizations. The methods are described in the sections devoted to radiation (Section 3.1) and cloud microphysics (Section 3.2), while the data sources are described in Appendix A. The methods include: (i) the introduction of aerosol information from external sources (CAMS) in near real-time, (ii) aerosol transport by advection, (iii) the description of aerosol effects on radiation processes, and (iv) the description of aerosol effects on cloud microphysics. We have seen sensitivity of the resulting radiation and precipitation fluxes to our modifications. However, before operational application, further studies are required to understand the impact of aerosol-related processes and interactions in detail”

This is only a first example of what is found in many other model modifications: please introduce a clear motivation behind for given modifications.

We have updated the text to include motivations for many modifications. Also, we explained different motivations in NWP developments and provided examples. See answers to previous comments.

In what follows, the authors present the three developments with the radiation that were made. Here, I would like to read how these three developments are interrelated. For example, the second development follows from the first?

Most of these are related to the representation of clouds. We have issues with fog/low visibility and the overestimation of cloud condensate in thick frontal clouds. The representation of clouds is sensitive to the CDNC, which were constants in the HARMONIE-AROME Cycle 40 and Cycle 43. We made changes to this (values and profile), which has improved the forecasts. These changes are described as “second development”. But the main improvement is expected from the use of NRT aerosols (“first development”), which will allow for a variable CDNC, both spatially and temporally. The other radiation related change is in the LW cloud liquid optical property scheme - a change was made to improve fog forecasts (using Cabauw data to retune the equation used in the model). This was further improved upon by K.P. Nielsen, who devised a new LW cloud liquid optical property scheme taking the LW bands into account. All improvements go in parallel, they do not follow one from another. We included an introduction statement:

“Changes in the radiation scheme of HARMONIE–AROME since Cycle 40 are related mainly to the effects of clouds and aerosols”

We also changed the text to make it clearer.

L120-121:  this is a rare occasion that the authors introduce a motivation for a modification, however in a backward manner: we introduce a modification to remove an existing problem. Here, it sounds like they only find an improvement only as an "after-fact", incidentally.

We changed the text to make it more clear. We changed the order of explanations:

“In HARMONIE–AROME Cycle 40, different values of CDNC were used in the radiation and microphysics schemes, which was an inconsistency. In HARMONIE–AROME Cycle 46, the radiation and microphysics schemes use the same prescribed base CDNC with assumed vertical distributions. Optionally, the use of the NRT aerosol data allows us to obtain the 3D CDNC fields and apply them consistently to both the radiation and cloud microphysics parametrizations (see Martín et al. and Section 3.2.2).”

L125, the remainder of this section is dedicated to......: what is the purpose of a phrase sounds like a special "fanfare" to introduce the third development: is there any particular importance?  Do we need a "special" space "dedicated" to describe this particular modification?  If not, this introductory phrase does not make any sense.

Reformulated. We have edited the text substantially, taking your feedback into account. 

Sec. 2.2 Convection, L158-160:

this lead sentence makes us think that this subsection is to going to describe the three boundary layer processes: clouds, turbulence, and cumulus convection. However, the subsection title suggests otherwise, and it appears that the latter is actually the case.

We have updated this and now called the section Convection, Turbulence and Statistical Cloud Scheme, with 3 subsections within it for convection, turbulence and the statistical cloud scheme.

L160-162: this general remark is what we need to read in the introduction.

We kept this remark here. The Introduction section now contains only very general statements and explanations. This is done to improve readability of the text, to make it possible for researchers outside the NWP community to understand it better. 

L164-165: this must be the lead sentence of this subsection.

We removed this sentence in the revised version.

However, here and elsewhere, the authors adopt a strange use of the verb "to focus":  when we say we focus on something, there must be a more general theme for a given subsection, and the verb "to focus" should suggest that under this general theme, the authors specify a "focus" of a presentation. Of course, this is merely a "focus", we expect to read some other remarks on a given more general subject.

“Focus” no longer appears in the paper.

Here, simply, this subsection "presents" changes with convection (and nothing else).

We have subsections for convection, turbulence and the statistical cloud scheme now.

Another examples of an odd use of the word "to focus" are found in e.g., L191-192.

All removed.

L157-165: I consider this paragraph as a whole a good example of a bad writing style of the present manuscript as a whole.

This has been rewritten.

L632-633: this kind of the presentations on the general configuration of HARMONIE-AROME is what the readers would like to read before the technical details of the radiation, etc. This would be the enough reason to put Sec. 4 before Sec. 2.

Yes we agree and have moved the sections around.

L666-667, CY46 and CY49: why and how the developments jump from CY46 to CY49? A detail that only the insiders would know, but the general readers would have no crew what the matters with CY49, rather than CY47.

This is now addressed in the introduction of the paper (as explained in answers to previous comments).

L671, severely outdated: this is a very informal discourse style. One needs a more specific motivation to replace a given scheme.

We have added more justifications:

“The ECMWF cy25r (ECMWF, 2015) radiation scheme used in HARMONIE-AROME is no longer maintained and is not up to date with recent developments in radiation schemes currently used in weather and climate models. Also, it lacks the flexibility to add new capabilities, as described in Grailet et al.”

L674, modern gas optics schemes: is it a technical term or does it just mean "more recently developed gas optics schemes"? Either the case, some elaborations as well as references are required.

We have rephrased and added the references:

“This scheme has been used in the IFS since Cycle 43R3 (Hogan et al.). Examples of improvements in the scheme are a more recently developed gas optics scheme with updated spectroscopy and the advanced TripleClouds (Shonk et al.) and SPARTACUS (Schäfer et al., Hogan et al., 2016, Hogan et al., 2019)  radiative transfer solvers, with the latter accounting for sub-grid cloud 3D radiative effects. The TripleClouds (Shonk et al.)  and SPARTACUS solvers were recently optimized, and when combined with the ecCKD (Hogan et al., 2022) spectrally reduced gas optics scheme, were found to be 13x and 2.5x faster respectively than the operational IFS radiation scheme (Ukkonen et al.).”

Sec. 5.2 title: to be changed to "scale aware shallow convection and turbulence", because this section covers both.

The changes only involve the convection scheme so adding Turbulence would be misleading here. The original ideas of Honnert2011 diagnose the total turbulent transport (so diffusive (Turbulence scheme) and convective) that is why they are mentioned. However, adaptations to the diffusive turbulence are not considered here as diffusive turbulence is related to much smaller scales than convection and not yet relevant at the resolutions we are aiming at. Obviously, under certain conditions and at very high resolution the turbulence scheme should also be adjusted (and be 3D ultimately). 

L713-714: These two sentences are hard follow, and also unclear how these two separate remarks about the two different subjects (boundary layer and convection) must be stated in sequence. Is there any general theme behind, or we are just reading two random remarks?  Please note that neither remark makes any sense without substantial expert knowledge.

We clarified the text. The boundary layer is used as an indication of the scale size of the convection which in turn is important to reduce the parameterization (together with the grid size of the model) along the ideas of Honnert 2011. 

“In Lancz et al. an approach to make the convection scheme scale aware is presented. The ideas for this approach originated from the work of Honnert et al. Based on coarse-graining of LES for several convective cases, the parameterized convective transport is reduced as a function of a non-dimensional grid size. Apart from the grid size itself, the non-dimensional grid size needs the boundary layer height as an estimate of the dominant scale of the convective transport. The larger the scale of the convective transport, the lower the resolution needed to resolve it. In HARMONIE-AROME an option similar to Lancz et al. is available.

As shown by Savazzi et al, with the boundary layer height for the non-dimensional grid size calculation, the scale of the transport is underestimated in the common case of organized convection. As a result, the reduction in the parameterized convection according to \cite{Lancz18}, during organized convective conditions, will be too small, and will hamper the model's ability to build up convection by itself. Therefore, we combine the scale aware convection scheme described above with another approach, first presented by Khain et al. In this approach, the parameterized convection is shut down if the absolute value of the resolved vertical velocity exceeds a certain value, indicating that the model has started to resolve (part of the) convection by itself. Preliminary results in HARMONIE-AROME using the combined approach of Lancz  et al. and Khain et al. are promising.”

L735, aerosol population: "aerosol distribution" could be clearer. However, do they also want to mean different categories of aerosols? I personally see a use of the term "aerosol" in the context of the microphysics could be misleading, because not all the aerosols are active as condensations nuclei, especially for the ice. Only the latter category of aerosol counts in the cloud microphysics.

“Aerosol population” is changed to “aerosol distribution”. Yes, not all aerosols are active. To stress this, we reformulated the next sentence:

“The prognostic concentration of active aerosols is used to calculate”

Sec. 5.5: in spite of the heading of this section, it actually begins by a general remark about the difficulties of progressing towards a fully convective resolving numerical weather forecasts. Extensive expected issues are rather thoroughly discussed in Yano et al. (2018 BAMS).  I should emphasize that this essay was written with extensive contributions of the HIRLAM-ALADIN community (as well as COSMO). Unfortunately, this section narrowly reduces the issues to the numerical algorithms for the dynamic core, and more specifically of the time integration scheme.  A good reminder of the general issues, or at least a reference to this essay would be warranted.

We have also included the Yano 2018 reference now - thanks for this suggestion.

End: I was surprised to read no conclusion in the manuscript. A short paragraph of wrap up would be helpful.

We have added a conclusion section.

References:

2. Provide a web link and/or the issue number for this technical report

We updated the bibtex entry. Url was already there but not appearing in print so added it after the cycle details.

32. "M'et'eo France" should be read "Météo France" or "M\'et\'eo France" in TeX

This has been updated.

101. Please update this reference. Has it been published or accepted? I could not find it on QJ web site.

Done.

Reviewer 3 Report

Comments and Suggestions for Authors

This manuscript is a technical note to describe the physical aspects included in a convection-permitting numerical weather prediction model. It covers advancements in physical parameterization, radiation schemes, microphysics, and surface physics. This technical note is important for understanding the model's performance and limitations.

 

The introduction provides a brief history of the HARMONIE-AROME forecast model. However, I still have some questions about this model: 1) Is this model accessible to the entire scientific community, or is it restricted to ACCORD members? 2) Will the simulations used in this manuscript be made publicly available? 3) Additionally, I believe the introduction would benefit from the inclusion of a schematic diagram illustrating the model, the scripting system, and the software infrastructure.

 

The methodology/results present a detailed description of the improvements in physical representations, particularly in radiation, aerosols, and chemical species. The new version of Cycle 46 configuration shows enhancement in radiation representation.

 

General considerations:

First, I noticed the absence of a clear definition of "Cycle 46." This definition should be included in both the Abstract and the Introduction for clarity.

Second, for all figures, I recommend adding a title at the top of the figures, and subtitles for each panel, labeling with letters (e.g. a), b), c)).

 

Third, the authors could include a Limitation Section, to summarize the model's unresolved shortcomings, such as the “spurious square-like ice-cloud” (Lines 362-367).

 

Finally, the authors could provide a comparative analysis of computational costs, runtime, and scalability across different hardware environments; this would be helpful for operational centers considering the implementation of Cycle 46.

 

Minor:

Line 73: There is an extra “)”.

Line 74: There is an extra “)” after “climatology [ 10 ]”

 

Author Response

This manuscript is a technical note to describe the physical aspects included in a convection-permitting numerical weather prediction model. It covers advancements in physical parameterization, radiation schemes, microphysics, and surface physics. This technical note is important for understanding the model's performance and limitations.

Thank you for your comments and for reviewing the paper.

The introduction provides a brief history of the HARMONIE-AROME forecast model. However, I still have some questions about this model: 1) Is this model accessible to the entire scientific community, or is it restricted to ACCORD members? 2) Will the simulations used in this manuscript be made publicly available? 3) Additionally, I believe the introduction would benefit from the inclusion of a schematic diagram illustrating the model, the scripting system, and the software infrastructure.

1. We have added info on the licensing to the conclusion section 
2. Yes we can provide the data if someone wants it but the files are large. The file format is FA and is hard to use without our internal software. Possible to provide grib files but would need the transition tables to use them.
3. We have included a schematic into the section “Dynamics, Model Configuration and System aspects”.

The methodology/results present a detailed description of the improvements in physical representations, particularly in radiation, aerosols, and chemical species. The new version of Cycle 46 configuration shows enhancement in radiation representation. 

Thank you.

General considerations:

First, I noticed the absence of a clear definition of "Cycle 46." This definition should be included in both the Abstract and the Introduction for clarity.

We have included the following in the Introduction:

“ACCORD shares some developments (parts of the code) with the European Center for Medium-Range Weather Forecasts (ECMWF) Integrated Forecasting System (IFS) model. This is possible due to the modularity of the code. To ensure consistency of the common code, ACCORD follows the releases of the IFS, known as cycles. When a new IFS cycle is issued, parts of the HARMONIE-AROME code are adjusted to collocate with it, and new developments are merged in. The basic cycle numbers for HARMONIE–AROME follow the IFS cycle numbering. Local developments of HARMONIE–AROME, starting from the basic IFS release, can lead to additional local releases. Because the process of merging and harmonisation is time-consuming, some IFS cycles are skipped. In this paper, we present the latest release of the HARMONIE-AROME Reference system, which is Cycle 46. Previous HARMONIE-AROME releases were based on Cycle 43. The release described in Bengtsson et al. was related to Cycle 40 and the next release will be Cycle 49.”

Second, for all figures, I recommend adding a title at the top of the figures, and subtitles for each panel, labeling with letters (e.g. a), b), c)).

We have added (a), (b) etc to the figures but prefer to keep the other details in the captions.

Third, the authors could include a Limitation Section, to summarize the model's unresolved shortcomings, such as the “spurious square-like ice-cloud” (Lines 362-367).

Unresolved shortcomings are numerous. To address these, we describe future developments in the section “Upcoming Developments in HARMONIE-AROME”. Problems are usually reported by forecasters, and we try to address these. The most pressing problems are the representation of fog and incorrect predictions of cold 2m temperatures during situations of the stable boundary layer. We added the following into the Conclusion section:

“Work is also on-going on the visibility parametrization, used by the model, as modelling low visibility events is still a challenge. The problem of correctly representing cold temperatures during stable conditions is also a challenge, which will need attention in the future.”

Finally, the authors could provide a comparative analysis of computational costs, runtime, and scalability across different hardware environments; this would be helpful for operational centers considering the implementation of Cycle 46.

- Testing is done locally as all centres need to achieve standard forecast runtime of about an hour at most.

Minor:

Line 73: There is an extra “)”.

Sentence has been changed.

Line 74: There is an extra “)” after “climatology [ 10 ]”

This is now fixed - in fact the sentence is edited also.

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

I much appreciate a very careful response of the authors to my original comments, that only rarely happens in my own experience.

As the authors respond, the manuscript has been thoroughly revised, and it it much smoother to read with more basic information required for the general readers provided.

I only find a single odd sentence in my own whole reading:

L30, three canonical system configurations (CSCs): by following this remark, the readers would naturally becomes curious what these three are.  However, in what follows, the authors only talk about HARMONIDE-AROME for a good reason.  It would suffice just to introduce HARMONIE-AROME as d"'one of the canonical system configurations (CSCs)", even without telling there are two others. The latter are simply not subjects.

Another issue that strikes me is the tendency of the authors to capitalize the key words (e.g., Cloud Microphysics). This is not a standard of English writing, but hopefully, the technical tedious can fix this problem.

It would be a good idea for the pathos for going through the manuscript again for final proof reading. Otherwise, I would be happy to let it go.

Comments on the Quality of English Language

the text could still be smoothed out

Author Response

Reviewer 2 (Round 2)

Comments and Suggestions for Authors

Comment 1: I much appreciate a very careful response of the authors to my original comments, that only rarely happens in my own experience.

Response 1: Many thanks for your kind words and for your reviews, which have helped greatly to improve the paper.

Comment 2: As the authors respond, the manuscript has been thoroughly revised, and it it much smoother to read with more basic information required for the general readers provided.

Response 2: Thank you.

Comment 3: I only find a single odd sentence in my own whole reading:

L30, three canonical system configurations (CSCs): by following this remark, the readers would naturally becomes curious what these three are.  However, in what follows, the authors only talk about HARMONIDE-AROME for a good reason.  It would suffice just to introduce HARMONIE-AROME as d"'one of the canonical system configurations (CSCs)", even without telling there are two others. The latter are simply not subjects.

Response 3: We have updated this. We mention AROME and ALARO in places in the paper so we have included the 3 CSCs as a list, with the acronyms spelt out also (see Introduction lines 29-34):

ACCORD cooperates on the development of a limited area NWP system, and shares software for parts of it. Historically, there are three canonical system configurations (CSCs) within the ACCORD NWP system maintained by different groupings of countries: 

• AROME (Applications of Research to Operations at Mesoscale) 
• HARMONIE-AROME (HIRLAM–ALADIN Research on Mesoscale Operational NWP in Euromed) 
• ALARO (Aire Limitee Adaptation/Application de la Recherche a l’Operationnel). 

Comment 4: Another issue that strikes me is the tendency of the authors to capitalize the key words (e.g., Cloud Microphysics). This is not a standard of English writing, but hopefully, the technical tedious can fix this problem.

Response 4: We have re-read the paper and fixed the capitalization issues.

Comment 5: It would be a good idea for the pathos for going through the manuscript again for final proof reading. Otherwise, I would be happy to let it go.

Response 5: This has been done also. 

Reviewer 3 Report

Comments and Suggestions for Authors

The authors addressed all the suggestions from the previous review. I don't have any more suggestions.

Author Response

Comment: The authors addressed all the suggestions from the previous review. I don't have any more suggestions.

Response: Thank you.