## 4 Discussion  
Figure 5 highlights some differences in the values provided in the two bulletins for the same parameter on the same day or same week, e.g., SO\({}_{2}\) flux of 250 t/day in weekly INGV bulletins versus 41 t/d by LGS, and VLP of 14 events/h in weekly INGV bulletins versus 9.2 events/h reported by LGS. These differences suggest that the typology and location of the two ground-based sensor stations, as well as the reference sampling period of the bulletins, should be carefully accounted for when interpreting the extracted values. Indeed, the INGV station measures the SO\({}_{2}\) flux through the FLAME network [19], which consists of four UV-scanning spectrometers installed near the coast of the island and intercepting the plume from a distance of 2000 m for the summit crater of Stromboli. On the other hand, LGS measures data by means of the ROC station, which is a site that allows the study of degassing activity nearer the volcano main crater, from 500 m of distance from the active events, and also offers an optimal view of the NE sector of the crater terrace [20]. In terms of the sampling period, LGS bulletins typically refer to a Friday to Thursday weekly interval, whereas INGV data refer to Monday to Sunday intervals; hence, there is a temporal shift in the identification of the reporting weeks by the two issuing institutes. In Figure 11, the SO\({}_{2}\) flux measured with the FLAME network (INGV) and at the ROC site (LGS) and reported in the respective weekly bulletins published in 2019 are plotted together. The general trends characterizing the two time series are comparable. Several missing INGV values in the series are due to omissions in text reports of the July-December period. We observe a similar trend for the SO\({}_{2}\) flux independently of the measuring stations and their location. Moreover, seismic time series reporting the VLP parameter for the complete dataset (2015-2021) are plotted in Figure 12. Data are recorded at the STR seismo-acoustic station that is deployed close to the crater zone. The VLP parameter gives a direct measure of the explosion rate [20]. Seismic values are similar for both the sources, when available. To confirm, we calculated the Pearson's correlatio  
Figure 11: Comparison of SO\({}_{2}\) flux measurements reported in INGV and LGS weekly bulletins during 2019. Figure 10: Histogram of the correlation between SO\({}_{2}\) and CO\({}_{2}\). definition) and obtained a 0.87 value, which demonstrates a coherent behavior of the two data series over time. In order to further verify the accuracy of the automatic extraction method from a qualitative point of view, we consider satellite monitoring information. The system is trained to tag some keywords identifying the presence of satellite information within the monitoring bulletins. In particular, we expect to find an interesting intersection between the presence of satellite monitoring information and SO\({}_{2}\) flux trends. For this purpose, time slots for which satellite observations are present are selected and time series of the gas flux and VLP trend are generated. In particular, we consider the LGS dataset that reports information on thermal activity based on MODIS sensor data. Considering the SO\({}_{2}\) flux plotted in Figure 13, it is possible to observe some peaks at the end of July and August 2019. In fact, two main paroxysms were registered on 3 July and 28 August [21]. The VLP trend confirms peaks of over 25 events/h on these dates (see Figure 14). Conversely, CO\({}_{2}\) time series are not reported because of the incompleteness due to the station destruction after the paroxysm of 3 July 2019. C/S time series are also not complete because of instrument malfunctioning (as reported in the daily LGS bulletin published on 4 July 2019). Figure 14: VLP time series for 2017–2021, extracted from LGS daily bulletins. Figure 12: Comparison of VLP events recorded in INGV and LGS bulletins in 2015–2021.