## 3 Results
### Aerosol Contamination Protection  
2.1 Aerosol Contamination Monitoring on a Synoptic Scale: The Saharan Dust Movement over the Mediterranean to Europe  
Comparing Al340/380 and Al354/388 images and cloud cover images obtained by the EUMETSAT MSG satellite (Figure 8), the Saharan sand transportation route coincides. Also, it is possible to notice that a difference between indices Al340/380 and Al354/388 exists, although it is minimal. The AI values in the Rijeka-Kvarner-Istria area were approximately from 1.25 to 2.5. On the south and the southwest, it was even higher. Such a high index indicates a high aerosol concentration and its sand origin. Figures also show a low AI index (a blue area) in the middle of high values, possibly because of the thick cloud cover presence. It should be checked separately in some of the deeper analyses and presented in future papers. However, it is important to note that, despite the cloud cover, an overview of the situation can still be obtained. It is worth remembering that the AI is calculated daily (Figure 8), and the presented cloud cover images (Figure 9) are recorded at 09 UTC and 18 UTC. Analysis of the surface measurements of the PM10 concentration showed its rise at the surface level on 20 June. The highest level (100-130 \(\upmu\)g/m\({}^{3}\)) was recorded on 21 June and in the first half of the next day. Later, concentrations fell below 50, and then below 30 \(\upmu\)g/m\({}^{3}\) (Figure 10). When comparing surface measurements with the AI, the coincidence is apparent. Figure 8: The Saharan sand movement over the Mediterranean to the European continent, 19 June 2024. Al340/380 (**a**), Al354/388 (**b**) [51]. Position coordinates are approximate. Figure 9: Cloud cover, EUMETSAT, Dust RGB, 19.06.2024. 09 UTC (**a**) and 18 UTC (**b**) [52; 53]. Position coordinates are approximate. 2.2 Aerosol Contamination Monitoring on a Mesoscale: The Faults in the 25 kV 50 Hz Electric Traction Network in Croatia  
The recorded aerosol indices in the Rijeka-Kvarner-Istria area are mainly from the interval [\(-\)5, 3] with a distribution close to normal, slightly skewed to the left with slightly positive kurtosis (0.36 for Al\({}_{340/380}\) and 0.61 for Al\({}_{354/388}\)) (Figure 11). The PM\({}_{10}\) particle distribution showed a significantly higher number of measured values lower than 100 \(\upmu\)g/m\({}^{3}\). Similarly, the aerosol height analysis showed that most aerosol is not spread too high in the atmosphere. It goes mainly up to 2500 m or to the pressure level of approximately 800 hPa. The comparison of the Sentinel 5p satellite records and PM\({}_{10}\) particle concentration measurements showed the power network outage appearance when AI values are negative (Figure 12) and positive (Figure 13) and when the PM\({}_{10}\) concentration is relatively high. Figure 11: Distribution of AI values in the Rijeka–Kvarner–Istria area. Figure 10: Concentration of PM\({}_{10}\) [\(\upmu\)g/m\({}^{3}\)] particles in Rijeka, Croatia, 20–22 June 2024. Figure 12: AI negative values (colored “\(\times\)”) and PM\({}_{10}\) particle concentrations (gray circle) on the day when outages appeared, 18 January 2022. Figure 13: AI positive values (colored “\(\times\)”) and PM\({}_{10}\) particle concentrations (gray circle) on the day when outages appeared, 6 February 2022. During the period when PM\({}_{10}\) particle concentrations were recorded at around 140-160 \(\mathrm{\SIUnitSymbolMicro}\)g/m\({}^{3}\) at some locations, the recorded AI values were close to minus two or minus three. At the same time, the aerosol mid-pressure was quite low (up to 850 hPa), and consequently the layer height was high (up to 1800 m). Recording the aerosol concentration at higher levels and having a significantly low AI may indicate that aerosols probably are not of sea salt origin. The presented example enables setting approximated limits of AI values when sea salt intrusion in the atmosphere is present.