the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 06 Dec 2022
Multi-model analysis of the Adriatic dense water dynamics
Abstract. This study aims to enhance our understanding of the bora-driven dense water dynamics in the Adriatic Sea using different state-of-the-art modelling approaches during the 2014–15 period. Practically, we analyse and compare the results of four different simulations: the latest reanalysis product for the Mediterranean Sea, the recently evaluated fine-resolution atmosphere-ocean Adriatic Sea climate model and the long-time running Adriatic Sea atmosphere-ocean forecast model used in both hindcast and data assimilation (with 4-day cycles) modes. As a first step, we evaluate the resolved physics in each simulation by focusing on the performance of the models. Then, we derive the general conditions in the ocean and the atmosphere during the investigated period. Finally, we analyse in detail the numerical reproduction of the dense water dynamics as seen by the four simulations. This study confirms that kilometre-scale atmosphere-ocean approach, non-hydrostatic atmospheric models, fine vertical resolutions in both atmosphere and ocean and proper location and forcing of the open boundary conditions are prerequisites for appropriate modelling of the ocean circulation in the Adriatic basin, which then may be improved by a data assimilation method. As proof, the 31-year long evaluation run of the Adriatic Sea climate model which meets these requirements is found to be able to outperform most aspects of the reanalysis product, the short-term hindcast and the data assimilated simulation, in reproducing the dense water dynamics in the Adriatic Sea.
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RC1: 'Comment on egusphere-2022-1274', Anonymous Referee #1, 05 Jan 2023
The MS presents a helpful analysis of the formation and collection of dense water in the Norther Adriatic during the bora (cold strong winds) events, and some insight into the transport of the newly formed dense bottom water to a greater depth. The authors post-processed previously obtained outputs form four models and calculated basic statistics in order to validate the models against archived observations in relation to the cascading process. They also used a combination of model outputs and observation to analyse the physics of bora-driven cascading.
The structure of the MS is slightly misleading. The Method section describes in much detail the methodology used in previous research, such as model set ups and parameters, which may give a false impression that the models were configured and run as part of this particular study. At the same time, the methods used in the present study are described only embryonically. The MS could be published after major revision to address the comments in this report.
Specific comments
The transport of dense water is the key element of dense water cascades. In the abstract, the authors claim ‘Finally, we analyse in detail the numerical reproduction of the dense water dynamics as seen by the four simulations.’ However, the dense water transport is described only qualitatively in the main text, and the assessment of the transport only appears in the appendix as ‘additional information’. The transport should be given much greater focus.
Lines 18-20 ‘This study confirms that … are prerequisites for appropriate modelling of the ocean circulation in the Adriatic basin’ . This is an overstatement. The study only reveals that one of the four models represents better some variables while other models are better in some other aspects. The paper does not proof that the named parameters are prerequisites for future research. Please re-word.
Introduction. The authors concentrate entirely on the Adriatic Sea. In order to make the results helpful for a wider oceanographic community the authors are advised to place the bora-driven cascading in a broader context. For example to compare briefly with cascades from other shelves, e.g. as discussed in (Ivanov et al, 2003, https://doi.org/10.1016/j.pocean.2003.12.002; GarciaâQuintana et al, 2021. https://doi.org/10.1029/2020JC016951)
Lines 69-70. ‘ ..the river climatology used in previous studies … has been replaced by a new climatology’. Please clarify, what is the difference between ‘old’ and ’new’ and give a reference. It seems from the text in Line 71 that the ‘new’ climatology was used in some ‘previous studies’.
Lines 78-79. ‘the most advanced variational scheme, the Four-Dimensional Variational…’. Which of the many versions and sub-versions of DA schemes is ‘the most advanced’ is a matter of discussion. Please re-word.
Line 81. ‘a 31-year evaluation simulation’ . Please define what is ‘evaluation simulation’. Was it run with or without DA?
Line 85 ‘the newest reanalysis product for the Mediterranean Sea’ . Please give a reference.
Line 95 and Line 98 ‘…between late autumn 2014 and summer 2015’ . ‘…between late November 2014 and mid-August 2015’ . Please exact dates as you do in Line 100.
Line 109. ‘..of various types of models’. This statement is too wide. Based on the results presented in the MS, the authors could only assess, contrast and compare the specific models they used, not the ‘types of models’.
Line 113.’ reanalysis product for the Mediterranean Sea’. Please give the exact product ID. Is it available from CMEMS catalogue? Is it MEDSEA_MULTIYEAR_PHY_006_004 ? If yes, please use the name for product given by the originators, namely ’Med MFC’ to avoid confusion. This product is generated not just by NEMO as stated in Lines 115-16 but ‘The Med MFC physical reanalysis product is generated by a numerical system composed of an hydrodynamic model, supplied by the Nucleous for European Modelling of the Ocean (NEMO) and a variational data assimilation scheme (OceanVAR)’ (https://data.marine.copernicus.eu/product/MEDSEA_MULTIYEAR_PHY_006_004/description)
Lines 113-200. The description of models from previous studies is too extensive, it should be reduced in size and moved from Material and methods to Introduction. Material and methods should present methodology used specifically for this study and in much greater detail than it is now.
Line 137. Please give a reference to the ALADIN/HR atmospheric model.
Lines 143-144. ‘In this model, the horizontal ROMS grid resolution is 2 km and there are 20 vertically spaced sigma levels controlled by the following parameters …’. Ocean model results are strongly dependent on the vertical resolution of a model. This is hinted by the authors in Lines 622-623 ’ In addition, the lack of vertical resolution in the ROMS-full model probably contributes to the improper representation of the dense water dynamics’. Has the sensitivity study been performed by the authors or other researchers? The authors attempt to compare ‘the types of the models’ however the skill of the same model can change significantly when model governing parameters or boundary conditions (e.g. river discharge) are changed. The authors should demonstrate that parameters of the models used for comparison provide the best results within the limitation of the specific ‘type’ of model in order to suggest which ‘type’ of the model is the best.
Lines 201-206. Have you noticed the ‘double penalty effect’ ( see e.g. https://doi.org/10.5194/os-16-831-2020 ) in the higher resolution models? If yes, how it impacts on the final results?
Line 202-203. ‘In order to compare different simulations, model results with grid resolution coarser than 1 km are interpolated to the AdriSCROMS 1 km grid…’ .Does it mean that all model outputs were also interpolated in the vertical to the AdriSCROMS sigma-coordinate grid with 35 levels? Please clarify.
Line 204-206’ For the ocean simulations, MEDSEA, ROMS-hind and ROMS-full results are regridded to 1 km resolution, while for the atmosphere, ERA5, ALADIN/HR-hind, ALADIN/HR-full and AdriSC-WRF results are all regridded to 1 km resolution.’ The use of the word ‘while’ is strange as all model outputs were regridded to the same scale. Please re-word.
Line 214-215. ‘ probability density functions of the biases (i.e., differences) between the results of the simulations and the in-situ temperature and salinity observations’ . This is the core component of methodology and it has to be described in much more detail. How the bias is calculated? If it is the average of all differences at all locations and all times then it would be impossible to calculate the PDF. Or is it an average of daily differences? Or something else?
Line 218. ‘The probability density functions are obtained with a kernel-smoothing method..’ Which kernel was used? What was the size of the smoothing window? The results may be sensitive to these factors. Please give more details here (including a reference) as otherwise your results cannot be replicated. An estimate of the sensitivity of results to the size of the smoothing window will be helpful.
Line 223. ‘minimum turbulent heat fluxes in the atmosphere’. Do you mean ‘minimum downward turbulent heat fluxes in the atmosphere at the sea surface’ Please clarify.
Line 230. ‘bottom PDA time series is presented without the seasonal signal which is removed from the series using the least-squares method.’ Please give more details of how PDAs are calculated otherwise the statement in Line 232 ‘the time evolution of the spatial distributions of the bottom PDAs’ is difficult to comprehend.
Lines 233-234. ‘An additional analysis (only presented and commented in Supplementary Material) quantifies the total daily volume transport of the outflowing dense waters..’ The near-bottom transport of dense waters is a major parameter quantifying the intensity of dense water cascades. Therefore it has to be included in the main text ( both results and discussion) in sufficient detail.
Lines 238-248. The validation of the four models against CTD casts is very helpful. In order to help a reader to interpret the figures given in this section, the methods of calculating biases given in the previous section have to be presented in much more detail. It is advisable to extend the basic stats ( mean and standard deviation) to include more advanced tools of model validation, e.g. Pearson correlation, Willmott skill parameter or Taylor diagram.
Lines 238-255. The four models have different resolutions and some of them may not resolve the processes of the scale of the baroclinic Rossby radius. Please provide a map of Rossby radius for your area. You may wish to use a simplified method presented in Chelton et al . 1998: Geographical variability of the first-baroclinic Rossby radius of deformation. J. Phys. Oceanogr., 28, 433-460.
Lines 301-302. ‘Overall, for all models, maximums of wind stresses are associated with bora events, while downward turbulent heat fluxes seem to be more influenced by the seasonal variations of the sea surface temperature’ . Please clarify the second part of this statement. From the qualitative point of view, stronger and colder winds (the bora) should have a greater influence on downward heat fluxes from the atmosphere to the ocean than smooth and therefore weaker seasonal variations.
Lines 345-416. The presentation of results is mostly concentrated on the atmosphere-ocean heat fluxes and the processes of formation of dense water. However, in contrast to CTD observations the models provide an opportunity to calculate dense water transport, which is a key component of cascading. This sections gives a good quantitative description of heat fluxes, while it describes the transports only qualitatively. This omission has to be rectified.
Citation: https://doi.org/10.5194/egusphere-2022-1274-RC1 -
AC1: 'Reply on RC1', Petra Pranić, 01 Mar 2023
Dear Referee #1,
Thank you very much for your detailed review which will highly contribute to the improvement of our article.
The transport of dense water is the key element of dense water cascades. In the abstract, the authors claim ‘Finally, we analyse in detail the numerical reproduction of the dense water dynamics as seen by the four simulations.’ However, the dense water transport is described only qualitatively in the main text, and the assessment of the transport only appears in the appendix as ‘additional information’. The transport should be given much greater focus.Response: The assessment of the transport will be placed in the main article as subsection 3.3.3.
Lines 18-20 ‘This study confirms that … are prerequisites for appropriate modelling of the ocean circulation in the Adriatic basin’ . This is an overstatement. The study only reveals that one of the four models represents better some variables while other models are better in some other aspects. The paper does not proof that the named parameters are prerequisites for future research. Please re-word.
Response: The sentences will be modified accordingly.
Introduction. The authors concentrate entirely on the Adriatic Sea. In order to make the results helpful for a wider oceanographic community the authors are advised to place the bora-driven cascading in a broader context. For example to compare briefly with cascades from other shelves, e.g. as discussed in (Ivanov et al, 2003, https://doi.org/10.1016/j.pocean.2003.12.002; Garcia Quintana et al, 2021. https://doi.org/10.1029/2020JC016951)
Response: A brief comparison will be added.
Lines 69-70. ‘ ..the river climatology used in previous studies … has been replaced by a new climatology’. Please clarify, what is the difference between ‘old’ and ’new’ and give a reference. It seems from the text in Line 71 that the ‘new’ climatology was used in some ‘previous studies’.
Response: A clarification will be added.
Lines 78-79. ‘the most advanced variational scheme, the Four-Dimensional Variational…’. Which of the many versions and sub-versions of DA schemes is ‘the most advanced’ is a matter of discussion. Please re-word.
Response: The sentence will be changed accordingly.
Line 81. ‘a 31-year evaluation simulation’ . Please define what is ‘evaluation simulation’. Was it run with or without DA?
Response: An explanation of the evaluation simulation will be added.
Line 85 ‘the newest reanalysis product for the Mediterranean Sea’ . Please give a reference.
Response: A reference will be added.
Line 95 and Line 98 ‘…between late autumn 2014 and summer 2015’ . ‘…between late November 2014 and mid-August 2015’ . Please exact dates as you do in Line 100.
Response: The Authors couldn't find the exact dates as they are not available in the original paper (Vilibić et al., 2018).
Line 109. ‘..of various types of models’. This statement is too wide. Based on the results presented in the MS, the authors could only assess, contrast and compare the specific models they used, not the ‘types of models’.
Response: The statement will be changed accordingly.
Line 113.’ reanalysis product for the Mediterranean Sea’. Please give the exact product ID. Is it available from CMEMS catalogue? Is it MEDSEA_MULTIYEAR_PHY_006_004 ? If yes, please use the name for product given by the originators, namely ’Med MFC’ to avoid confusion. This product is generated not just by NEMO as stated in Lines 115-16 but ‘The Med MFC physical reanalysis product is generated by a numerical system composed of an hydrodynamic model, supplied by the Nucleous for European Modelling of the Ocean (NEMO) and a variational data assimilation scheme (OceanVAR)’ (https://data.marine.cop ernicus.eu/product/MEDSEA_MULTIYEAR_PHY_006_004/description)
Response: Yes, the reanalysis product is MEDSEA_MULTIYEAR_PHY_006_004. The name of the product stated in Escudier et al. (2020) is „Med MFC“. The Authors agree that „Med MFC“ is the best name in order to avoid any confusion. However, Escudier et al. (2021) referred to the same reanalysis as „MEDREA24“ for the purpose of their study. Thus, the Authors chose the name „MEDSEA“ just for the purpose of this study and would like to keep the name for practical reasons. The product descripton will be changed accordingly.
Lines 113-200. The description of models from previous studies is too extensive, it should be reduced in size and moved from Material and methods to Introduction. Material and methods should present methodology used specifically for this study and in much greater detail than it is now.
Response: A summary of the main features of the models will be added in the form of a table in Material and methods, while a short paragraph about the models will be added to the Introduction. Also, the full description of the models will be modified and transfered to the Supplemet S2. The main focus will be placed on the methodology which will be described in greater detail.
Line 137. Please give a reference to the ALADIN/HR atmospheric model.
Response: A reference will be added.
Lines 143-144. ‘In this model, the horizontal ROMS grid resolution is 2 km and there are 20 vertically spaced sigma levels controlled by the following parameters …’. Ocean model results are strongly dependent on the vertical resolution of a model. This is hinted by the authors in Lines 622-623 ’ In addition, the lack of vertical resolution in the ROMS-full model probably contributes to the improper representation of the dense water dynamics’. Has the sensitivity study been performed by the authors or other researchers? The authors attempt to compare ‘the types of the models’ however the skill of the same model can change significantly when model governing parameters or boundary conditions (e.g. river discharge) are changed. The authors should demonstrate that parameters of the models used for comparison provide the best results within the limitation of the specific ‘type’ of model in order to suggest which ‘type’ of the model is the best.
Response: A sensitivity study has not been performed as we only use already well validated models – i.e., the skills of each model have previously been assessed (= the best parametrization possible are used) and this is not the aim of this study to redo this assessment. However, the forcing used in the different models (rivers, boundary conditions, etc.) are discussed at length in the paper.
Lines 201-206. Have you noticed the ‘double penalty effect’ ( see e.g. https://doi.org/10.5194/os-16-831-2020 ) in the higher resolution models? If yes, how it impacts on the final results?
Response: A comment about the „double-penalty effect“ will be added.
Line 202-203. ‘In order to compare different simulations, model results with grid resolution coarser than 1 km are interpolated to the AdriSCROMS 1 km grid…’ .Does it mean that all model outputs were also interpolated in the vertical to the AdriSCROMS sigma-coordinate grid with 35 levels? Please clarify.
Response: Model outputs were not interpolated in the vertical, thus the sentence will be modified.
Line 204-206’ For the ocean simulations, MEDSEA, ROMS-hind and ROMS-full results are regridded to 1 km resolution, while for the atmosphere, ERA5, ALADIN/HR-hind, ALADIN/HR-full and AdriSC-WRF results are all regridded to 1 km resolution.’ The use of the word ‘while’ is strange as all model outputs were regridded to the same scale. Please re-word.
Response: The sentence will be modified.
Line 214-215. ‘ probability density functions of the biases (i.e., differences) between the results of the simulations and the in-situ temperature and salinity observations’ . This is the core component of methodology and it has to be described in much more detail. How the bias is calculated? If it is the average of all differences at all locations and all times then it would be impossible to calculate the PDF. Or is it an average of daily differences? Or something else?
Response: An explanation of the bias calculation will be added to the Methods section.
Line 218. ‘The probability density functions are obtained with a kernel-smoothing method..’ Which kernel was used? What was the size of the smoothing window? The results may be sensitive to these factors. Please give more details here (including a reference) as otherwise your results cannot be replicated. An estimate of the sensitivity of results to the size of the smoothing window will be helpful.
Response: A more detailed description of PDFs will be added to the Methods section.
Line 223. ‘minimum turbulent heat fluxes in the atmosphere’. Do you mean ‘minimum downward turbulent heat fluxes in the atmosphere at the sea surface’ Please clarify.
Response: Yes, minimum downward turbulent heat fluxes in the atmosphere at the sea surface are presented. The sentence will be modified accordingly.
Line 230. ‘bottom PDA time series is presented without the seasonal signal which is removed from the series using the least-squares method.’ Please give more details of how PDAs are calculated otherwise the statement in Line 232 ‘the time evolution of the spatial distributions of the bottom PDAs’ is difficult to comprehend.
Response: The PDA calculation will be described in greater detail in the Methods section.
Lines 233-234. ‘An additional analysis (only presented and commented in Supplementary Material) quantifies the total daily volume transport of the outflowing dense waters..’ The near-bottom transport of dense waters is a major parameter quantifying the intensity of dense water cascades. Therefore it has to be included in the main text ( both results and discussion) in sufficient detail.
Response: The section about dense water transport will be included in the main text.
Lines 238-248. The validation of the four models against CTD casts is very helpful. In order to help a reader to interpret the figures given in this section, the methods of calculating biases given in the previous section have to be presented in much more detail. It is advisable to extend the basic stats ( mean and standard deviation) to include more advanced tools of model validation, e.g. Pearson correlation, Willmott skill parameter or Taylor diagram.
Response: The validation statistics will be extended with a Taylor diagram and a paragraph will be added to subsection 3.1.
Lines 238-255. The four models have different resolutions and some of them may not resolve the processes of the scale of the baroclinic Rossby radius. Please provide a map of Rossby radius for your area. You may wish to use a simplified method presented in Chelton et al . 1998: Geographical variability of the first-baroclinic Rossby radius of deformation. J. Phys. Oceanogr., 28, 433-460.
Response: A map and time series of the baroclinic Rossby radii for the Adriatic Sea will be added to the article.
Lines 301-302. ‘Overall, for all models, maximums of wind stresses are associated with bora events, while downward turbulent heat fluxes seem to be more influenced by the seasonal variations of the sea surface temperature’ . Please clarify the second part of this statement. From the qualitative point of view, stronger and colder winds (the bora) should have a greater influence on downward heat fluxes from the atmosphere to the ocean than smooth and therefore weaker seasonal variations.
Response: The statement refers to the fact that in December and January the days are shorter than the rest of the year. Consequently, there are less solar radiations during these months and the sea surface temperature is colder than usual. This seems to affect the values of the downward heat fluxes. The Authors however agree that the above formulation might not be so clear.
Lines 345-416. The presentation of results is mostly concentrated on the atmosphereocean heat fluxes and the processes of formation of dense water. However, in contrast to CTD observations the models provide an opportunity to calculate dense water transport, which is a key component of cascading. This sections gives a good quantitative description of heat fluxes, while it describes the transports only qualitatively. This omission has to be rectified.
Response: The Authors agree and a quantitative description of transports will be added to the main article.
Citation: https://doi.org/10.5194/egusphere-2022-1274-AC1
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AC1: 'Reply on RC1', Petra Pranić, 01 Mar 2023
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RC2: 'Comment on egusphere-2022-1274', Anonymous Referee #2, 15 Feb 2023
The MS presents a nice analysis of the dynamics of the bora driven circulation in the Norther Adriatic during 2014-2015. The authors work with outputs form four simulations. The statistical study is interesting to validate the numerical results against the real observations.
Although the article is good overall, it needs some improvements especially in the methods used in this study which should be more detailed, but also the circulation of the dense water should be more emphasized.
The last line of the abstract is a bit strong in the sense that the article does not prove that 1-the spatial scale, 2-non hydrostatic, 3-fine resolution and 4-forcing at the open boundary are pre-requisites, it only shows us that one simulation, of the four taken into account, is better than the others and it is closest to the dynamic theory of the behavior of the northern Adriatic basin.
The calculations of the probability density functions should be given in more detail, perhaps a sensitivity study of the method should be mentioned.
Also, the seasonal signal removed from the PDA time series would be shown.
The numerical models used in the study have different resolutions, so a comment regarding the numerical resolution of processes with different Rossby's radius deformation would be important.
Vertical resolution can also play a large role in improperly representing the dynamics of dense water. Therefore, the same model can change significantly as the parameters that govern it vary as well as the boundary conditions. This should be described in more detail even if not verified.
Also, the 31-years simulation should be described in more detail.
The authors are very focused on heat fluxes, but a good model would also allow to estimate the transport of dense water
Citation: https://doi.org/10.5194/egusphere-2022-1274-RC2 -
AC2: 'Reply on RC2', Petra Pranić, 01 Mar 2023
Dear Referee #2,
Thank you very much for your review which will contribute to the improvement of our article.
The last line of the abstract is a bit strong in the sense that the article does not prove that 1-the spatial scale, 2-non hydrostatic, 3-fine resolution and 4-forcing at the open boundary are pre-requisites, it only shows us that one simulation, of the four taken into account, is better than the others and it is closest to the dynamic theory of the behavior of the northern Adriatic basin.Response: The abstract will be modified accordingly.
The calculations of the probability density functions should be given in more detail, perhaps a sensitivity study of the method should be mentioned.
Response: Calculations of the probability density functions will be described in more detail.
Also, the seasonal signal removed from the PDA time series would be shown.
Response: Time series with the seasonal signal are shown on Fig. 7.
The numerical models used in the study have different resolutions, so a comment regarding the numerical resolution of processes with different Rossby's radius deformation would be important.
Response: A comment about the resolution and the Rossby radii will be added.
Vertical resolution can also play a large role in improperly representing the dynamics of dense water. Therefore, the same model can change significantly as the parameters that govern it vary as well as the boundary conditions. This should be described in more detail even if not verified.
Response: The influence of the vertical resolution will be described.
Also, the 31-years simulation should be described in more detail.
Response: The 31-year simulation will be described in more detail.
The authors are very focused on heat fluxes, but a good model would also allow to estimate the transport of dense water
Response: More focus will be placed on the transport of dense water.
Citation: https://doi.org/10.5194/egusphere-2022-1274-AC2
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AC2: 'Reply on RC2', Petra Pranić, 01 Mar 2023
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2022-1274', Anonymous Referee #1, 05 Jan 2023
The MS presents a helpful analysis of the formation and collection of dense water in the Norther Adriatic during the bora (cold strong winds) events, and some insight into the transport of the newly formed dense bottom water to a greater depth. The authors post-processed previously obtained outputs form four models and calculated basic statistics in order to validate the models against archived observations in relation to the cascading process. They also used a combination of model outputs and observation to analyse the physics of bora-driven cascading.
The structure of the MS is slightly misleading. The Method section describes in much detail the methodology used in previous research, such as model set ups and parameters, which may give a false impression that the models were configured and run as part of this particular study. At the same time, the methods used in the present study are described only embryonically. The MS could be published after major revision to address the comments in this report.
Specific comments
The transport of dense water is the key element of dense water cascades. In the abstract, the authors claim ‘Finally, we analyse in detail the numerical reproduction of the dense water dynamics as seen by the four simulations.’ However, the dense water transport is described only qualitatively in the main text, and the assessment of the transport only appears in the appendix as ‘additional information’. The transport should be given much greater focus.
Lines 18-20 ‘This study confirms that … are prerequisites for appropriate modelling of the ocean circulation in the Adriatic basin’ . This is an overstatement. The study only reveals that one of the four models represents better some variables while other models are better in some other aspects. The paper does not proof that the named parameters are prerequisites for future research. Please re-word.
Introduction. The authors concentrate entirely on the Adriatic Sea. In order to make the results helpful for a wider oceanographic community the authors are advised to place the bora-driven cascading in a broader context. For example to compare briefly with cascades from other shelves, e.g. as discussed in (Ivanov et al, 2003, https://doi.org/10.1016/j.pocean.2003.12.002; GarciaâQuintana et al, 2021. https://doi.org/10.1029/2020JC016951)
Lines 69-70. ‘ ..the river climatology used in previous studies … has been replaced by a new climatology’. Please clarify, what is the difference between ‘old’ and ’new’ and give a reference. It seems from the text in Line 71 that the ‘new’ climatology was used in some ‘previous studies’.
Lines 78-79. ‘the most advanced variational scheme, the Four-Dimensional Variational…’. Which of the many versions and sub-versions of DA schemes is ‘the most advanced’ is a matter of discussion. Please re-word.
Line 81. ‘a 31-year evaluation simulation’ . Please define what is ‘evaluation simulation’. Was it run with or without DA?
Line 85 ‘the newest reanalysis product for the Mediterranean Sea’ . Please give a reference.
Line 95 and Line 98 ‘…between late autumn 2014 and summer 2015’ . ‘…between late November 2014 and mid-August 2015’ . Please exact dates as you do in Line 100.
Line 109. ‘..of various types of models’. This statement is too wide. Based on the results presented in the MS, the authors could only assess, contrast and compare the specific models they used, not the ‘types of models’.
Line 113.’ reanalysis product for the Mediterranean Sea’. Please give the exact product ID. Is it available from CMEMS catalogue? Is it MEDSEA_MULTIYEAR_PHY_006_004 ? If yes, please use the name for product given by the originators, namely ’Med MFC’ to avoid confusion. This product is generated not just by NEMO as stated in Lines 115-16 but ‘The Med MFC physical reanalysis product is generated by a numerical system composed of an hydrodynamic model, supplied by the Nucleous for European Modelling of the Ocean (NEMO) and a variational data assimilation scheme (OceanVAR)’ (https://data.marine.copernicus.eu/product/MEDSEA_MULTIYEAR_PHY_006_004/description)
Lines 113-200. The description of models from previous studies is too extensive, it should be reduced in size and moved from Material and methods to Introduction. Material and methods should present methodology used specifically for this study and in much greater detail than it is now.
Line 137. Please give a reference to the ALADIN/HR atmospheric model.
Lines 143-144. ‘In this model, the horizontal ROMS grid resolution is 2 km and there are 20 vertically spaced sigma levels controlled by the following parameters …’. Ocean model results are strongly dependent on the vertical resolution of a model. This is hinted by the authors in Lines 622-623 ’ In addition, the lack of vertical resolution in the ROMS-full model probably contributes to the improper representation of the dense water dynamics’. Has the sensitivity study been performed by the authors or other researchers? The authors attempt to compare ‘the types of the models’ however the skill of the same model can change significantly when model governing parameters or boundary conditions (e.g. river discharge) are changed. The authors should demonstrate that parameters of the models used for comparison provide the best results within the limitation of the specific ‘type’ of model in order to suggest which ‘type’ of the model is the best.
Lines 201-206. Have you noticed the ‘double penalty effect’ ( see e.g. https://doi.org/10.5194/os-16-831-2020 ) in the higher resolution models? If yes, how it impacts on the final results?
Line 202-203. ‘In order to compare different simulations, model results with grid resolution coarser than 1 km are interpolated to the AdriSCROMS 1 km grid…’ .Does it mean that all model outputs were also interpolated in the vertical to the AdriSCROMS sigma-coordinate grid with 35 levels? Please clarify.
Line 204-206’ For the ocean simulations, MEDSEA, ROMS-hind and ROMS-full results are regridded to 1 km resolution, while for the atmosphere, ERA5, ALADIN/HR-hind, ALADIN/HR-full and AdriSC-WRF results are all regridded to 1 km resolution.’ The use of the word ‘while’ is strange as all model outputs were regridded to the same scale. Please re-word.
Line 214-215. ‘ probability density functions of the biases (i.e., differences) between the results of the simulations and the in-situ temperature and salinity observations’ . This is the core component of methodology and it has to be described in much more detail. How the bias is calculated? If it is the average of all differences at all locations and all times then it would be impossible to calculate the PDF. Or is it an average of daily differences? Or something else?
Line 218. ‘The probability density functions are obtained with a kernel-smoothing method..’ Which kernel was used? What was the size of the smoothing window? The results may be sensitive to these factors. Please give more details here (including a reference) as otherwise your results cannot be replicated. An estimate of the sensitivity of results to the size of the smoothing window will be helpful.
Line 223. ‘minimum turbulent heat fluxes in the atmosphere’. Do you mean ‘minimum downward turbulent heat fluxes in the atmosphere at the sea surface’ Please clarify.
Line 230. ‘bottom PDA time series is presented without the seasonal signal which is removed from the series using the least-squares method.’ Please give more details of how PDAs are calculated otherwise the statement in Line 232 ‘the time evolution of the spatial distributions of the bottom PDAs’ is difficult to comprehend.
Lines 233-234. ‘An additional analysis (only presented and commented in Supplementary Material) quantifies the total daily volume transport of the outflowing dense waters..’ The near-bottom transport of dense waters is a major parameter quantifying the intensity of dense water cascades. Therefore it has to be included in the main text ( both results and discussion) in sufficient detail.
Lines 238-248. The validation of the four models against CTD casts is very helpful. In order to help a reader to interpret the figures given in this section, the methods of calculating biases given in the previous section have to be presented in much more detail. It is advisable to extend the basic stats ( mean and standard deviation) to include more advanced tools of model validation, e.g. Pearson correlation, Willmott skill parameter or Taylor diagram.
Lines 238-255. The four models have different resolutions and some of them may not resolve the processes of the scale of the baroclinic Rossby radius. Please provide a map of Rossby radius for your area. You may wish to use a simplified method presented in Chelton et al . 1998: Geographical variability of the first-baroclinic Rossby radius of deformation. J. Phys. Oceanogr., 28, 433-460.
Lines 301-302. ‘Overall, for all models, maximums of wind stresses are associated with bora events, while downward turbulent heat fluxes seem to be more influenced by the seasonal variations of the sea surface temperature’ . Please clarify the second part of this statement. From the qualitative point of view, stronger and colder winds (the bora) should have a greater influence on downward heat fluxes from the atmosphere to the ocean than smooth and therefore weaker seasonal variations.
Lines 345-416. The presentation of results is mostly concentrated on the atmosphere-ocean heat fluxes and the processes of formation of dense water. However, in contrast to CTD observations the models provide an opportunity to calculate dense water transport, which is a key component of cascading. This sections gives a good quantitative description of heat fluxes, while it describes the transports only qualitatively. This omission has to be rectified.
Citation: https://doi.org/10.5194/egusphere-2022-1274-RC1 -
AC1: 'Reply on RC1', Petra Pranić, 01 Mar 2023
Dear Referee #1,
Thank you very much for your detailed review which will highly contribute to the improvement of our article.
The transport of dense water is the key element of dense water cascades. In the abstract, the authors claim ‘Finally, we analyse in detail the numerical reproduction of the dense water dynamics as seen by the four simulations.’ However, the dense water transport is described only qualitatively in the main text, and the assessment of the transport only appears in the appendix as ‘additional information’. The transport should be given much greater focus.Response: The assessment of the transport will be placed in the main article as subsection 3.3.3.
Lines 18-20 ‘This study confirms that … are prerequisites for appropriate modelling of the ocean circulation in the Adriatic basin’ . This is an overstatement. The study only reveals that one of the four models represents better some variables while other models are better in some other aspects. The paper does not proof that the named parameters are prerequisites for future research. Please re-word.
Response: The sentences will be modified accordingly.
Introduction. The authors concentrate entirely on the Adriatic Sea. In order to make the results helpful for a wider oceanographic community the authors are advised to place the bora-driven cascading in a broader context. For example to compare briefly with cascades from other shelves, e.g. as discussed in (Ivanov et al, 2003, https://doi.org/10.1016/j.pocean.2003.12.002; Garcia Quintana et al, 2021. https://doi.org/10.1029/2020JC016951)
Response: A brief comparison will be added.
Lines 69-70. ‘ ..the river climatology used in previous studies … has been replaced by a new climatology’. Please clarify, what is the difference between ‘old’ and ’new’ and give a reference. It seems from the text in Line 71 that the ‘new’ climatology was used in some ‘previous studies’.
Response: A clarification will be added.
Lines 78-79. ‘the most advanced variational scheme, the Four-Dimensional Variational…’. Which of the many versions and sub-versions of DA schemes is ‘the most advanced’ is a matter of discussion. Please re-word.
Response: The sentence will be changed accordingly.
Line 81. ‘a 31-year evaluation simulation’ . Please define what is ‘evaluation simulation’. Was it run with or without DA?
Response: An explanation of the evaluation simulation will be added.
Line 85 ‘the newest reanalysis product for the Mediterranean Sea’ . Please give a reference.
Response: A reference will be added.
Line 95 and Line 98 ‘…between late autumn 2014 and summer 2015’ . ‘…between late November 2014 and mid-August 2015’ . Please exact dates as you do in Line 100.
Response: The Authors couldn't find the exact dates as they are not available in the original paper (Vilibić et al., 2018).
Line 109. ‘..of various types of models’. This statement is too wide. Based on the results presented in the MS, the authors could only assess, contrast and compare the specific models they used, not the ‘types of models’.
Response: The statement will be changed accordingly.
Line 113.’ reanalysis product for the Mediterranean Sea’. Please give the exact product ID. Is it available from CMEMS catalogue? Is it MEDSEA_MULTIYEAR_PHY_006_004 ? If yes, please use the name for product given by the originators, namely ’Med MFC’ to avoid confusion. This product is generated not just by NEMO as stated in Lines 115-16 but ‘The Med MFC physical reanalysis product is generated by a numerical system composed of an hydrodynamic model, supplied by the Nucleous for European Modelling of the Ocean (NEMO) and a variational data assimilation scheme (OceanVAR)’ (https://data.marine.cop ernicus.eu/product/MEDSEA_MULTIYEAR_PHY_006_004/description)
Response: Yes, the reanalysis product is MEDSEA_MULTIYEAR_PHY_006_004. The name of the product stated in Escudier et al. (2020) is „Med MFC“. The Authors agree that „Med MFC“ is the best name in order to avoid any confusion. However, Escudier et al. (2021) referred to the same reanalysis as „MEDREA24“ for the purpose of their study. Thus, the Authors chose the name „MEDSEA“ just for the purpose of this study and would like to keep the name for practical reasons. The product descripton will be changed accordingly.
Lines 113-200. The description of models from previous studies is too extensive, it should be reduced in size and moved from Material and methods to Introduction. Material and methods should present methodology used specifically for this study and in much greater detail than it is now.
Response: A summary of the main features of the models will be added in the form of a table in Material and methods, while a short paragraph about the models will be added to the Introduction. Also, the full description of the models will be modified and transfered to the Supplemet S2. The main focus will be placed on the methodology which will be described in greater detail.
Line 137. Please give a reference to the ALADIN/HR atmospheric model.
Response: A reference will be added.
Lines 143-144. ‘In this model, the horizontal ROMS grid resolution is 2 km and there are 20 vertically spaced sigma levels controlled by the following parameters …’. Ocean model results are strongly dependent on the vertical resolution of a model. This is hinted by the authors in Lines 622-623 ’ In addition, the lack of vertical resolution in the ROMS-full model probably contributes to the improper representation of the dense water dynamics’. Has the sensitivity study been performed by the authors or other researchers? The authors attempt to compare ‘the types of the models’ however the skill of the same model can change significantly when model governing parameters or boundary conditions (e.g. river discharge) are changed. The authors should demonstrate that parameters of the models used for comparison provide the best results within the limitation of the specific ‘type’ of model in order to suggest which ‘type’ of the model is the best.
Response: A sensitivity study has not been performed as we only use already well validated models – i.e., the skills of each model have previously been assessed (= the best parametrization possible are used) and this is not the aim of this study to redo this assessment. However, the forcing used in the different models (rivers, boundary conditions, etc.) are discussed at length in the paper.
Lines 201-206. Have you noticed the ‘double penalty effect’ ( see e.g. https://doi.org/10.5194/os-16-831-2020 ) in the higher resolution models? If yes, how it impacts on the final results?
Response: A comment about the „double-penalty effect“ will be added.
Line 202-203. ‘In order to compare different simulations, model results with grid resolution coarser than 1 km are interpolated to the AdriSCROMS 1 km grid…’ .Does it mean that all model outputs were also interpolated in the vertical to the AdriSCROMS sigma-coordinate grid with 35 levels? Please clarify.
Response: Model outputs were not interpolated in the vertical, thus the sentence will be modified.
Line 204-206’ For the ocean simulations, MEDSEA, ROMS-hind and ROMS-full results are regridded to 1 km resolution, while for the atmosphere, ERA5, ALADIN/HR-hind, ALADIN/HR-full and AdriSC-WRF results are all regridded to 1 km resolution.’ The use of the word ‘while’ is strange as all model outputs were regridded to the same scale. Please re-word.
Response: The sentence will be modified.
Line 214-215. ‘ probability density functions of the biases (i.e., differences) between the results of the simulations and the in-situ temperature and salinity observations’ . This is the core component of methodology and it has to be described in much more detail. How the bias is calculated? If it is the average of all differences at all locations and all times then it would be impossible to calculate the PDF. Or is it an average of daily differences? Or something else?
Response: An explanation of the bias calculation will be added to the Methods section.
Line 218. ‘The probability density functions are obtained with a kernel-smoothing method..’ Which kernel was used? What was the size of the smoothing window? The results may be sensitive to these factors. Please give more details here (including a reference) as otherwise your results cannot be replicated. An estimate of the sensitivity of results to the size of the smoothing window will be helpful.
Response: A more detailed description of PDFs will be added to the Methods section.
Line 223. ‘minimum turbulent heat fluxes in the atmosphere’. Do you mean ‘minimum downward turbulent heat fluxes in the atmosphere at the sea surface’ Please clarify.
Response: Yes, minimum downward turbulent heat fluxes in the atmosphere at the sea surface are presented. The sentence will be modified accordingly.
Line 230. ‘bottom PDA time series is presented without the seasonal signal which is removed from the series using the least-squares method.’ Please give more details of how PDAs are calculated otherwise the statement in Line 232 ‘the time evolution of the spatial distributions of the bottom PDAs’ is difficult to comprehend.
Response: The PDA calculation will be described in greater detail in the Methods section.
Lines 233-234. ‘An additional analysis (only presented and commented in Supplementary Material) quantifies the total daily volume transport of the outflowing dense waters..’ The near-bottom transport of dense waters is a major parameter quantifying the intensity of dense water cascades. Therefore it has to be included in the main text ( both results and discussion) in sufficient detail.
Response: The section about dense water transport will be included in the main text.
Lines 238-248. The validation of the four models against CTD casts is very helpful. In order to help a reader to interpret the figures given in this section, the methods of calculating biases given in the previous section have to be presented in much more detail. It is advisable to extend the basic stats ( mean and standard deviation) to include more advanced tools of model validation, e.g. Pearson correlation, Willmott skill parameter or Taylor diagram.
Response: The validation statistics will be extended with a Taylor diagram and a paragraph will be added to subsection 3.1.
Lines 238-255. The four models have different resolutions and some of them may not resolve the processes of the scale of the baroclinic Rossby radius. Please provide a map of Rossby radius for your area. You may wish to use a simplified method presented in Chelton et al . 1998: Geographical variability of the first-baroclinic Rossby radius of deformation. J. Phys. Oceanogr., 28, 433-460.
Response: A map and time series of the baroclinic Rossby radii for the Adriatic Sea will be added to the article.
Lines 301-302. ‘Overall, for all models, maximums of wind stresses are associated with bora events, while downward turbulent heat fluxes seem to be more influenced by the seasonal variations of the sea surface temperature’ . Please clarify the second part of this statement. From the qualitative point of view, stronger and colder winds (the bora) should have a greater influence on downward heat fluxes from the atmosphere to the ocean than smooth and therefore weaker seasonal variations.
Response: The statement refers to the fact that in December and January the days are shorter than the rest of the year. Consequently, there are less solar radiations during these months and the sea surface temperature is colder than usual. This seems to affect the values of the downward heat fluxes. The Authors however agree that the above formulation might not be so clear.
Lines 345-416. The presentation of results is mostly concentrated on the atmosphereocean heat fluxes and the processes of formation of dense water. However, in contrast to CTD observations the models provide an opportunity to calculate dense water transport, which is a key component of cascading. This sections gives a good quantitative description of heat fluxes, while it describes the transports only qualitatively. This omission has to be rectified.
Response: The Authors agree and a quantitative description of transports will be added to the main article.
Citation: https://doi.org/10.5194/egusphere-2022-1274-AC1
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AC1: 'Reply on RC1', Petra Pranić, 01 Mar 2023
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RC2: 'Comment on egusphere-2022-1274', Anonymous Referee #2, 15 Feb 2023
The MS presents a nice analysis of the dynamics of the bora driven circulation in the Norther Adriatic during 2014-2015. The authors work with outputs form four simulations. The statistical study is interesting to validate the numerical results against the real observations.
Although the article is good overall, it needs some improvements especially in the methods used in this study which should be more detailed, but also the circulation of the dense water should be more emphasized.
The last line of the abstract is a bit strong in the sense that the article does not prove that 1-the spatial scale, 2-non hydrostatic, 3-fine resolution and 4-forcing at the open boundary are pre-requisites, it only shows us that one simulation, of the four taken into account, is better than the others and it is closest to the dynamic theory of the behavior of the northern Adriatic basin.
The calculations of the probability density functions should be given in more detail, perhaps a sensitivity study of the method should be mentioned.
Also, the seasonal signal removed from the PDA time series would be shown.
The numerical models used in the study have different resolutions, so a comment regarding the numerical resolution of processes with different Rossby's radius deformation would be important.
Vertical resolution can also play a large role in improperly representing the dynamics of dense water. Therefore, the same model can change significantly as the parameters that govern it vary as well as the boundary conditions. This should be described in more detail even if not verified.
Also, the 31-years simulation should be described in more detail.
The authors are very focused on heat fluxes, but a good model would also allow to estimate the transport of dense water
Citation: https://doi.org/10.5194/egusphere-2022-1274-RC2 -
AC2: 'Reply on RC2', Petra Pranić, 01 Mar 2023
Dear Referee #2,
Thank you very much for your review which will contribute to the improvement of our article.
The last line of the abstract is a bit strong in the sense that the article does not prove that 1-the spatial scale, 2-non hydrostatic, 3-fine resolution and 4-forcing at the open boundary are pre-requisites, it only shows us that one simulation, of the four taken into account, is better than the others and it is closest to the dynamic theory of the behavior of the northern Adriatic basin.Response: The abstract will be modified accordingly.
The calculations of the probability density functions should be given in more detail, perhaps a sensitivity study of the method should be mentioned.
Response: Calculations of the probability density functions will be described in more detail.
Also, the seasonal signal removed from the PDA time series would be shown.
Response: Time series with the seasonal signal are shown on Fig. 7.
The numerical models used in the study have different resolutions, so a comment regarding the numerical resolution of processes with different Rossby's radius deformation would be important.
Response: A comment about the resolution and the Rossby radii will be added.
Vertical resolution can also play a large role in improperly representing the dynamics of dense water. Therefore, the same model can change significantly as the parameters that govern it vary as well as the boundary conditions. This should be described in more detail even if not verified.
Response: The influence of the vertical resolution will be described.
Also, the 31-years simulation should be described in more detail.
Response: The 31-year simulation will be described in more detail.
The authors are very focused on heat fluxes, but a good model would also allow to estimate the transport of dense water
Response: More focus will be placed on the transport of dense water.
Citation: https://doi.org/10.5194/egusphere-2022-1274-AC2
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AC2: 'Reply on RC2', Petra Pranić, 01 Mar 2023
Peer review completion
Journal article(s) based on this preprint
Data sets
Multi-model analysis of the Adriatic dense water dynamics: assets Petra Pranić https://osf.io/9jvk3/
Model code and software
AdriSC Climate Model: evaluation run Cléa Lumina Denamiel https://doi.org/10.17605/OSF.IO/ZB3CM
Video supplement
Multi-model analysis of the Adriatic dense water dynamics: assets Petra Pranić https://osf.io/9jvk3/
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Cléa Lumina Denamiel
Ivica Janeković
Ivica Vilibić
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