An Operational Supporting System for Oil Spill Emergencies Addressed to the the Italian Coast Guard

Round 1

Reviewer 1 Report

The article describes an interesting study involving experiments in the marine environment and referring them to mathematical simulations.

Main comments:

1) Do the developed models take into account the temperature and salinity of water? The impact of these environmental factors on oil dispersion in the marine environment should be discussed.

2) There is no discussion (in my opinion chapter 2 is only a discussion)

3) Lines 234-247 are not a discussion of results. If rewritten, they can be used for discussion and as final conclusions.

4) The conclusions should be thoroughly rewritten and shortened. In addition, the article and conclusions do not clearly indicate whether these models are already being used or are still planned to be used in practice? This should be clarified. If this model is used in practice, are there any effects that have been confirmed on a large scale and not only experimentally?.

5) What is the possibility of a wider use of the models in other marine areas (or are they dedicated/limited only for selected areas of the Mediterranean Sea)?

6) Is is possible that using two (out of three) hierarchical levels results in lower accuracy of predictions?

7) Table 1 should be supplemented with the size and time of the petroleum product spills, as well as API values.

8) What was the temperature of water and air during the experiments? What is the speed of sea currents in this region?

9) What was the depth of the experimental oil spills (the article can be supplemented with issues related to whether the depth  of the spill has any influence on the spread of oil).

Comments for author File: Comments.pdf

Author Response

The authors sincerely thank the Reviewer 1 for her/his constructive comments and recommendations which definitively helped in improving readability and quality of the paper. All the comments are addressed accordingly and have been incorporated to the revised manuscript. Detailed responses to comments and recommendations follow.

Main comments:

1) REVIEWER: Do the developed models take into account the temperature and salinity of water? The impact of these environmental factors on oil dispersion in the marine environment should be discussed.

AUTHORS: The oil spill model MEDSLIK_II requires the wind forcing, the sea surface temperature and the sea currents as inputs. The wind forcing is provided by the atmospheric forecasting model Skiron, while currents and temperature by sub-regional forecasting ocean models. The sea surface temperature is used to compute the evaporation rate (Mackay et al., 1980), while the currents for the oil spill spreading (see equation n.1). The salinity has not any impact on the spreading, except for the determination of the density field of the seawater. A study of the impact of the sea surface temperature is not discussed in the paper because it is negligible than other chemico-physical parameters such as °API.

2) REVIEWER:  There is no discussion (in my opinion chapter 2 is only a discussion)

AUTHORS: Chapter 2 is the presentation of the methods, i.e. the description of the numerical system and the graphical interface. We renamed the Section “Conclusion” with “Discussion and Conclusion” where we added, after a revision, what suggested by the referee at her/his point 3 (please see the following). With this choice, without any stop given by a new section, we think to give more readability to the final part of the paper and its conclusions.

3) REVIEWER: Lines 234-247 are not a discussion of results. If rewritten, they can be used for discussion and as final conclusions.

AUTHORS: We thank the referee for this comment. We rephrased this part and move it in the following section “Discussion and Conclusion” as follows (L.251-262)

“In fact, as demonstrated by the tests, the type of spill (massive or constant over time) can determine a significant difference in the concentration of oil-slick on the sea surface. This is due to the action of the spatial and temporal variability of the advection fields that act during the oil-spill modifying the oil concentration. Even the type of oil °API) has a significant impact on the evolution of OFP, especially on the fraction that tends to evaporate °API belonging to the light classes) and on that to disperse in the water column °API belonging to the heavy class). Consequently, the fraction of oil that remains on the sea surface represents an estimate of the initially dispersed percentage that should be recovered. Furthermore, close to the coast, or where the circulation is not adequately resolved by the hydrodynamic forecasting system, it is necessary to carry out further scenarios by correcting the numerical solution through the inclusion of the Wind Drift Correction term effect. This term, as previously seen, can considerably modify both the evolution of the OFPs (due to the occurrence of the beaching process) and the spatial distribution of the concentration.”

4) REVIEWER: The conclusions should be thoroughly rewritten and shortened. In addition, the article and conclusions do not clearly indicate whether these models are already being used or are still planned to be used in practice? This should be clarified. If this model is used in practice, are there any effects that have been confirmed on a large scale and not only experimentally?.

AUTHORS: As previously written we merged discussion and conclusions in a unique section to permit a higher readability of the final part of the paper. And, as suggested, we strongly revised this section answering referee's questions:

The oil spill predicting system is already used in practice for real emergencies and exercises, in particular we refer to this sentence in the conclusion: “the oil spill prediction system is actually used for real pollution emergencies, and also in case of antipollution exercises at sea, such as the recent one named POLLEX2020, coordinated by the Italian Coast Guard to test their intervention readiness.”

Furthermore, this complex forecast system has been operational and in use by the Italian Coast Guard since July 2020.

5) REVIEWER: What is the possibility of a wider use of the models in other marine areas (or are they dedicated/limited only for selected areas of the Mediterranean Sea)?

AUTHORS: All the forecast circulation and then the oil spill prediction models can be implemented all over the marine areas, but initial and boundary conditions (T; S; bathymetry, weather forecast, etc…) are necessary.

6) REVIEWER: Is is possible that using two (out of three) hierarchical levels results in lower accuracy of predictions?

AUTHORS: The prediction accuracy (oil spill dispersion) is independent by the hierarchical levels, but it depends by the accuracy of the numerical solution of the weather and ocean models.

The third hierarchical level of the DSS concerns the operational activities realized by the response agencies (Coast Guard, etc…) at sea, like logistic plans.

7) REVIEWER: Table 1 should be supplemented with the size and time of the petroleum product spills, as well as API values.

AUTHORS: Thanks for the suggestion, table 1 has been changed accordingly.

8) REVIEWER: What was the temperature of water and air during the experiments? What is the speed of sea currents in this region?

AUTHORS: Unfortunately, we have not any observation in nearly real time in the study area. Sea water and air temperature are both taken into account by the ocean model, coming as inputs from ocean and weather regional models, then we have just their estimations. The GUI does not show water and air temperature (used to computed the evaporation rate), while it shows the maps of sea surface currents (over the entire study area) and wind speed (only at the centre of the oil slick). Please see this at Figure 6.

9) REVIEWER: What was the depth of the experimental oil spills (the article can be supplemented with issues related to whether the depth  of the spill has any influence on the spread of oil).

AUTHORS: Thanks for this comment. We have clarified in the text that the experiments are all at the sea surface (L.202).

All numerical experiments have been performed at the sea surface because MEDSLIK_II is not three-dimensional, but it includes the dispersion (the vertical particles positions), but the dispersion in water column (below the water surface) is simply parameterized by a random walk scheme. (Buist 1979; Mackay et al., 1979).

Author Response File: Author Response.pdf

Reviewer 2 Report

The authors present an oil spill monitoring system that focuses on an area of the Mediterranean Sea. The system integrates different modules. Some of them are based on numerical modeling of the dynamics of the fluids involved in the phenomenon. In my opinion, the paper is of interest to the research community

The paper describes the bases and functionalities of some of the parts, although it does not describe in detail the design requirements (referred to the different types of end-user) from which it starts.
It is quite hard to follow the connection between the modules. I think that a general description of the system, following the scheme of Fig. 1 (including the utility of the GUI for validation), before the detailed description of the modules would be very beneficial.

 

 

 

Author Response

The authors present an oil spill monitoring system that focuses on an area of the Mediterranean Sea. The system integrates different modules. Some of them are based on numerical modeling of the dynamics of the fluids involved in the phenomenon. In my opinion, the paper is of interest to the research community

REVIEWER: The paper describes the bases and functionalities of some of the parts, although it does not describe in detail the design requirements (referred to the different types of end-user) from which it starts.
It is quite hard to follow the connection between the modules. I think that a general description of the system, following the scheme of Fig. 1 (including the utility of the GUI for validation), before the detailed description of the modules would be very beneficial.

AUTHORS: The authors would like to thank the Reviewer 2 for his/her thoughtful comments which have improved the manuscript. In the following we address the specific suggestion in order to clarify the complex structure of the prediction system.

L.59-79: The oil spill forecasting system (Figure 1) includes two main numerical modules and one GUI (Section 2.3).

The core of the system is the oil spill dispersion model (Section 2.1) which produces oil dispersion maps and trajectories, validated by drifter observations. This model is forced by the forecast sea currents and wind provided by the circulation module (Section 2.2). The latter consists of a Sub-Regional ocean forecasting system, forced in turn by means of a Weather Forecasting System and boundary conditions coming from a Regional ocean forecasting system. The whole SOS-Piattaforme system is used by the Italian Coast Guard by means of a GUI (Section 2.3), i.e. a user-friendly and simple interface which allows either to execute the simulations and visualize the results and validation reports. The information about the spilled oil can come from direct communications following the accident or from airplane/satellite data.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Authors made a very good work! They took into consideration all the suggestions and modified the MS. I appreciated a lot their work. I think the paper is now suitable to be published.