One of the most visible anthropogenic effects on the atmosphere is the condensation trails or contrails. Contrails form for various reasons but the most important is the emission of water vapour. In order that contrails can form, air in aircraft’s plume must become saturated with water vapour. Beside visual pollution, contrails can affect the radiation budget of the surface-atmosphere system.
In this master thesis analysis of radiosonde measurements is made (measurements taken in period 21. 10. 2004-12. 05. 2019), using Schmidt-Appleman criterion, which can be used to determine if contrail can form according to environment variables and properties of an aircraft. With a usage of the Schmidt-Appleman criterion computation is made to determine occurrence of the possible contrails above Slovenia. In addition to the criterion for contrail formation, persistence of contrails requires that ambient air is frost-saturated.
Analysis has shown, that only in rare cases the state of the atmosphere is not suitable for formation of potential contrails. On the other hand, only 30 % off all analysed days was suitable for formation of potential persistent contrails. It is interesting that only rarely potential contrails are visible from the ground. This is, because of the lower clouds, that obstruct the view.
Mean thickness of the region, where contrails can form, depends strongly on season. In colder winter months mean thickness is significantly larger than in hot summer months. Criterion for contrails depends in first place on environmental temperature and in second place on relative humidity. In the time series for upper and lower boundary of the region, where criterion for contrails is fulfilled, there are mostly no statistically significant linear trends. The same applies for percentage of days when Schmidt-Appleman criterion is fulfilled.