This paper provides essential information to the researchers in the same study field, particularly scientists interested in mass transport and water quality in an enclosed basin. The authors conducted significant field observations with respect and completed further analysis by using numerical simulations. However, there are some incoherences in the manuscript. For example, the authors mention the importance of the Coriolis effect on a gyre, but there is no detailed explanation and discussion. Also, the authors need to add more literature on a gyre in an enclosed basin. Please see more details below. As mentioned above, this study could provide significant contributions after revising the manuscript. Therefore, I recommend a substantial revision of the manuscript.

1) Is only one meteorological station available despite the huge lake size?

2) Why is there only one transect in the eastern area?

3) In the Materials and Methods, the authors need to mention more details about the field observations, such as the observation period.

4) In lines 291 to 293, the authors mentioned, "the three-gyre pattern in the first mode is predominantly controlled by the spatial and temporal variations of wind stress". However, there is only one meteorological station. How did the authors investigate the spatial effect of wind on a gyre?

5) Spatially variable winds are one of the major driving forces in many lakes and bays, such as Lake Michigan [Schwab and Beletsky, JGR, 2003], Lake Kinneret [Laval et al., L&O, 2003], Lake Tahoe [Rueda et al., JGR, 2005], Lake Biwa [Shimizu et al., L&O, 2007], and Tokyo Bay [Nakayama et al., JGR, 2014]. Could you provide any information on the spatial variation of the wind in Lake Geneva? Also, please add more discussion about the effect of wind stress curl on the occurrence of surface-layer circulation.

6) The authors mention, "Coriolis force plays an important role in the formation of gyres since the width of the lake is much larger than the internal Rossby radius of deformation". I agree with it. Indeed, the authors included the Coriolis effect in numerical simulations. However, there is no investigation and discussion about the Coriolis effect on a gyre. For example, in the northern hemisphere, the vertical velocity at the gyre centre is positive when the wind curl is positive. However, there is a criterion that the vertical velocity changes from negative to positive, depending on whether the Ekman pumping is dominant. Could you add more explanation about the Coriolis effect on a gyre in the Results and Discussion?

7) In Figures 7 and 8, the arrows need to be improved as it is difficult to understand what they show.

8) In lines 513 to 516, the authors mention the importance of upwelling and downwelling on large lake ecological systems. Only the authors describe the upwelling phenomenon in line 415 in the Results (Figure 10). There is no detailed explanation for it.

9) The paper includes vital information and outcomes. However, it is not easy to follow how the authors obtain the consequences. Could you restructure the study contents to let readers efficiently understand the significance of the study?

The study was carried out via comprehensive methods, including numerical models, remote sensing observations, and field observations. It made important contributions to the studies on (sub)mesoscale hydrodynamic motions and bio-geo-chemical process, and it also provided a successful example for how numerical model can be used to instruct the design of field campaigns.

Except for some minor issues in the text and figure descriptions, more detailed descriptions about the decomposition of OW parameter should be provided in the method and supplied in the results. Also, the effect from Coriolis force and thermal stratification should be further discussed if that is still within the scope of the study. I recommend the manuscript should be accepted subject to minor revisions. Please find my specific comments below:

• Abstract: the abstract contains too much introduction. More focus should be put on the major results you found via applying the numerical model and in field observations.
• Line 88-89: this sentence is not necessary.
• More discussion about the effect from Coriolis force and seasonal stratification on the gyres’ size, lifetime, and boundary are required.
• The meteorological data used to drive the numerical model were from the atmospheric model, but the wind information showed in Fig. 5 and used to identify the event was from Buchillon field station. Have you compared the model input with the realistic wind data? How is the spatial variation in the wind field? The statement or comparison figure are required to clarify that.
• Fig. 2: Describe the sources of inset images in the figure.
• Line 230: Is there any specific reason for choosing September? Due to the availability of Satellite data? Or thermal stratification is vanishing in this month?
• Line 248-249: Why? The combine effect of Coriolis force?
• Fig. 3: What do the percentages in the figure represent?
• Fig. 5: Are the values in (a) and (c) integrated over a specific time range? Can you give more explanation about how you decomposed OW parameter? In (e) and (f), the information is blur here. Why OW parameter is negative when Pown is positive? Does that mean Eown and Pown always have opposite signs?
• Line 404: Is that because the spatial resolution of the field measurement is not fine enough?
• Line 423: Did you record the lifetime of them?
• Fig. 9: description of panel (h)?
• Line 497-499: You have said that in the result part.