## 3 Results and Discussion  
Figure 2A shows the temporal variations in the night-time and daytime COS mixing ratios, as well as the long-term and seasonal variations obtained from only considering the daytime data (n = 11,315 out of 46,860 data points) using the CCGvu curve-fitting procedure. \begin{table}
\begin{tabular}{c c c c c} \hline
**Budget** & **Type of Flux** & **Total (GgS yr\({}^{-1}\))** & **SD * (GgS yr\({}^{-1}\))** & **Data Source** \\ \hline \multirow{3}{*}{Net sinks} & Vegetation & \(-\)576 & 7 & [27] revised in [28] \\  & Oxic soils & \(-\)126 & 5 & [28] \\  & Atmospheric oxidation by OH & \(-\)100 & - & [30] \\  & Photolysis in the stratosphere & \(-\)30 & - & [30] \\ \cline{2-5}  & Anoxic soils & +96 & 2 & [28] \\  & Anthropogenic & +394 & 21 & [31] \\  & Oceanic & +313 & 14 & [32] **, [33; 34] *** \\  & Biomass burning & +48 & 9 & [35] \\ \hline \end{tabular}  
* Standard deviation. ** For direct emissions. *** For indirect emissions (via CS\({}_{2}\) and DMS, respectively).  
\end{table} 
Table 1: Fluxes from the different COS source and sink components. Mean magnitude and standard deviations of the fluxes are given for the period 2009–2016. The spring maximum and the autumn minimum are depicted by a series of red dots. The relevant data for autumn 2017 are missing because no other instrument was operational during that time to fill the data gap. In other words, the CCGvu curve fitting realistically represents the magnitude of the springtime COS maximum of the year 2020, but not that of autumn 2017, because the daytime mixing ratios at the TRN site were proven not to have  
Figure 2: The GIF COS time series (2014–2021) analyzed using the CCGvu curve fitting procedure ((**A**) seasonal variations in the smooth curve (blue curve) calculated solely from daytime data ((11–17 h UTC), cyan dots) where the spring maximum and autumn minimum are depicted by red dots; the long-term trend depicted in orange, was also calculated from daytime data). May 15 th was set as the upper limit for the detection of the spring maximum, see text. Night-time data (22–04 h UTC) are depicted in black. A few data points over 650 ppt were removed to better visualize the seasonal variability in COS. Annual trends in the spring maximum and autumn minimum ((**B**) in blue and red dots, respectively) and in the seasonal cycle amplitude **(C**)** are shown, including the 95% confidence intervals. exceeded 500 ppt during the French lockdown due to the COVID-19 pandemic [19]. The daytime COS measurements show variability in seasonal and interannual timescales. The record undergoes a seasonal cycle with a peak in spring and a trough in autumn (Figure 2A). Note the presence in early summer of a shoulder on the fitting curve, which occasionally evolves into a secondary maximum. During this period, the COS enhancements are higher during night-time than daytime (Figure 2A). This is consistent with the existence of COS emissions from agroecosystems in late spring--early summer, when wheat and rapeseed are grown within the footprint of the monitoring station [19], where nocturnal stability allows the accumulation of COS near the ground until vertical mixing recovers the next morning. Hence, to draw a distinction between the date of the spring maximum and that of the summer, we set May 15 th as the upper limit for the detection of the spring maximum. The results also show that the spring maximum declined at a rate of \(-8.2\) ppt/year (\(-49\) ppt over 6 years). The autumn minimum showed a similar trend, although it was less steady and had a lower rate, of \(-1.7\) ppt/year (\(-10\) ppt over 6 years, Figure 2B). Intriguingly, the amplitude of the seasonal cycle at GIF decreased unsteadily from 2015, at a rate of \(-4.4\) ppt yr\({}^{-1}\), totaling \(-27\) ppt over 6 years (Figure 2C). The lowest value in terms of magnitude of the spring maximum and SCA was recorded during the year 2021.