## 4 Conclusions  
The Gif-sur-Yvette time series (August 2014 to November 2021), made of 46,860 hourly measurements of the atmospheric COS mixing ratio carried out at 7 m above ground level, was analyzed for significant trends in seasonal to multi-year scales. These long-term measurements provided critical constraints on the budget of the COS in the footprint area of the GIF station. The daytime spring maximum and the seasonal cycle amplitude (SCA) exhibited decreasing trends during the 2015-2021 time period. This points to a causal relationship, implying that the SCA is essentially driven by the COS plant uptake in response to changes in the atmospheric background of this gas, as the ORCHIDEE and other land-surface models show. However, when previously documented surface fluxes were transported using the LMDz atmospheric transport model, the simulated and observed seasonal variations in the COS exhibited large discrepancies in terms of amplitude and phase. This points to a likely misrepresentation of the marine and anthropogenic surface fluxes in the footprint area of the GIF site. We look forward to the performance of a more accurate model simulation to represent the marine and anthropogenic components with, in this latter case, particular attention paid to the emissions from the most recent decade, which are yet to be inventoried.  
**Supplementary Materials:** The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/atmos13050812/s1](https://www.mdpi.com/article/10.3390/atmos13050812/s1)]([https://www.mdpi.com/article/10.3390/atmos13050812/s1](https://www.mdpi.com/article/10.3390/atmos13050812/s1)). Figure S1: Simulations of the mean seasonal cycle of tropospheric COS mixing ratios over the years 2011-2015 (left column, NH mean annual atmospheric COS concentration in the range 483.7-491.5 ppt) and 2016-2019 (right column, decreasing NH mean annual atmo-spheric COS concentration in the range 486.9-467.8 ppt, see Figure 3) at the GIF (A,C) and MHD (B,D) monitoring stations. These simulations only account for the first-order relationship between the COS plant/soil fluxes and NH mean annual atmospheric COS concentrations. The net signal (black line) was obtained from a global LMDz simulation using all the dominant sources and sinks, while the signal components (colored lines) were obtained by running the global atmospheric simulation with one component flux at a time. Observations are shown in grey (dashed line). Here, optimized marine emissions (cf., Figure 4) were used instead of the standard ones.  
**Author Contributions:** Conceptualization, methodology, data curation, writing--original draft preparation, S.B., M.R. ([PERSON]), and C.A.; software, M.R. ([PERSON]) and C.A.; writing--review and editing, F.M., M.R. ([PERSON]), and P.P.; visualization, S.B., M.R. ([PERSON]), and C.A. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research received no external funding.  
**Institutional Review Board Statement:** Not applicable, studies not involving humans or animals.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** Data supporting reported results can be found at [[https://doi.org/10.1](https://doi.org/10.1)]([https://doi.org/10.1](https://doi.org/10.1)) 4768/6800b065-dcc-4006-ada5-b5f62a4 bb832 (accessed on 24 March 2022).  
**Acknowledgments:** The authors thank the three reviewers for their constructive and useful comments, which helped to further improve this study. We also acknowledge [PERSON] for providing the oceanic flux data.  
**Conflicts of Interest:** The authors declare no conflict of interest.