Influence of the Coriolis Force on Spreading of River Plumes

Round 1

Reviewer 1 Report

Based on analyzing optical satellite imagery (Sentinel-2 and Landsat 8) of river plumes located in different parts of the World Ocean and combing with synchronous wind data obtained from ERA5 reanalysis, the paper answered whether the deflection of individual river plumes is stable under various wind forcing conditions, whether the deflection stable for different river plumes at similar latitudes.  Besides, the relation between latitude and deflection angle for small and medium-size river plumes was proposed. This is interesting and valuable.  By comprehensive consideration, I suggest to accept this paper after the authors further consider the following questions and suggestions:

 As the readers of Remote Sensing are almost remote sensing workers, the are unnecessary to be familiar with the dynamics of estuary and the coastal zone, so I suggest the authors to added some key points to the paper, e.g. the method to calculate the deflection angles (DA).

 

I suggest to added how to extract the plume spreading direction from a satellite images, what the accuracy of the extraction is, and whether the accuracy can meet the analysis in the paper or not (how much impact it has made on the analysis).

If possible, I suggest the authors to further attach the data set of the interpretation results of the plume spreading direction together with the wind direction for each river plumes showed in Figure 1 as a supplement material.

Author Response

Many thanks for these valuable comments and suggestions, which served to improve the article. According to your recommendations, we added to the text:

(1) the main information about the dynamics of river plumes in the coastal zone (added to Introduction);

(2) the detailed description of the method to calculate the deflection angles from satellite images, as well as the related discussion about its accuracy (added to Data and Methods);

(3) the data set of plume spreading directions and wind directions as a supplementary material.

Reviewer 2 Report

1. What is the main question addressed by the research?

 

The paper is dedicated to the study of the Coriolis force influence on river plumes spreading. The authors were focused on deflection of plumes from wind direction induced by the Coriolis force.

 

 

2. Do you consider the topic original or relevant in the field, and if so, why?

 

The topic is original and relevant in the field. The authors have analyzed extensive set of Landsat 8 and Sentinel-2 satellite images of multiple small and medium-size river plumes at different parts of the World Ocean and synchronous wind reanalysis data. They have shown that the deflection angle is stable for individual river plumes for different wind directions, albeit with certain limitations related to wind speed and coastal morphology. The deflection angle is similar for river plumes located at similar latitudes and varies from ~0° near the Equator to 15-25° in temperate zones and ~30° in polar zones. They also have derived a direct relation between latitude and the deflection angle.

 

 

3. What does it add to the subject area compared with other published material?

 

Many previous studies demonstrated that spreading direction of river plumes (especially small plumes) generally coincides with wind direction. At the same time, the majority of river plumes are strongly affected by the Coriolis force, which is also among the baseline knowledge about the plumes. So, the authors were focused on deflection of plumes from wind direction induced by the Coriolis force. They have shown that the deflection angle is stable for individual river plumes for different wind directions, albeit with certain limitations related to wind speed and coastal morphology. The deflection angle is similar for river plumes located at similar latitudes and varies from ~0° near the Equator to 15-25° in temperate zones and ~30° in polar zones. They also have derived a direct relation between latitude and the deflection angle. The obtained results improved understanding the universal features of river plume dynamics. They are important for monitoring and forecasting of delivery and fate of fluvial water and river-borne matter in different coastal regions of the World Ocean.

 

 

4. What specific improvements could the authors consider regarding the methodology?

 

There is no need to make any improvements or something else. The authors outlined shortly the current achievements in the field in the introduction, and provided detailed description of the materials and method, as well as the obtained results, their discussion, and conclusions.

 

 

5. Are the conclusions consistent with the evidence and arguments presented and do they address the main question posed?

 

The conclusions are consistent with the evidence and arguments presented in the manuscript and address the main questions of their study.

 

 

6. Are the references appropriate?

 

The references are appropriate.

 

 

7. Please include any additional comments on the tables and figures.

 

All the tables and figures are appropriate. They show well the research and experiment details and results.

Please, provide dimension for ‘Deflection angle’ in Figure 7.

 

 

8. Other comments.

 

Please, provide the future research plans in this area in Conclusions.

 

 

After detailed consideration of the manuscript, I have found that the results obtained are new and significant for the field. The manuscript is written well and can be published as is. Only two small corrections indicated earlier are required.

 

 

So, the paper needs at least a minor revision.

Author Response

 Many thanks for your evaluation of the manuscript and your suggestions. According to your recommendations, we corrected Figure 7 and added future research plans to the Conclusions.

Reviewer 3 Report

The paper addresses the Coriolis effect on the deviation of the river plumes on sea in North and South hemispheres. The authors give a simple and clear linear law between latitude and deflection angle (page 10, Fig 7). The wind data source is meteorological reanalysis ERA5 and the images of plume geometries are sentinel-2 and landsat-8 origins. The paper is concise and pleasant to follow; nevertheless, it appears that many details could be added to describe in a better way the research conducted. Here under it follows our suggestions.

Science

The methodology to extract the orientation of the up-wind plume side from the satellite imagery could be mentioned. The construction of the curves presented on the figure may be detailed and particularly the tangent vector used.

The uncertainties on the wind direction could be detailed. The statistical variance may be detailed.

The Coriolis effect in the sea current could have a 3D dimension; as well the Ekman layer is a twist in the water depth. The paper could address why 2D surface and essentially wind effect (*) is sufficient for the explanation of the plume deviation.

(*)SADRINASAB, Masoud, EINALI, Abbas, AKBARINASAB, Mohammad, et al. Numerical Modelling of Arvandrud River Plume and the impact of wind and River Discharge on the plume structure By Three Dimensional and Hydro dynamical Model (FVCOM). Journal of Marine Science and Technology, 2021, vol. 20, no 3, p. 12-30.

It may be mentioned that water depth, water salinity play minor roles compared to wind effect. These ones are integrated in 3D ocean hydrodynamic. The Kerch strait was the location of major oil-spills consecutive to a storm in November 2007 (article Matishov, water ressources, 2013). Oil plumes (oil seeps) dynamics are driven by sea current (article Mityagina and Lavrova, remote sensing, 2022).

Edition

Coastal power plant could generate plume and it may be mentioned. Pollution on the sea surface coming from river may be mentioned.

Island may be added to the list l 112.

A wind rose could present the wind the plume side tangent and the deflection angle i.e. one could be placed on each plume figure.

The paper could state that the interface (freshwater/saltwater) turns right (?) on the North hemisphere and turn left in the South hemisphere. A schematic view of these effects could be made for clearness.

Typo

Check three line 137

Author Response

Many thanks for these valuable comments and suggestions, which served to improve the article. According to your recommendations, we added to the text:

(1) the detailed description of the method to calculate the deflection angles from satellite images, as well as the related discussion about its accuracy (added to Data and Methods);

 (2) discussion why wind effect is sufficient for the explanation of the plume deviation, i.e., why the Coriolis effect does not result in formation of the Coriolis curl in presence of the stratified river plume (added to Introduction);

(3) discussion about the differences in spreading dynamics of river plumes, oil plumes, suspended and floating pollutants, thermal plumes (added to Discussion);

(4) description about right/left deflection of motion affected by the Coriolis force in the Northern/Southern hemispheres (added to Introduction), as well as the related scheme (added to Figure 1).

Round 2

Reviewer 3 Report

The revised manuscript contains a sufficient number of added details and discussions. Consequently, we recommend accepting the paper.

The precision about the angle 5.3° for an expected 10° value should be appreciated (line 199). It could be considered with future oceanographic models and in-situ studies comparisons.

Avoiding generalisation of the study is welcome at the end of the section discussion conclusion.

Deflection angle calculation is well defined at the end of section 2, Data and methods.

We appreciate the scheme on the Coriolis effect on figure 1.