Photos of contrails in the Cypriot sky are increasingly appearing on social networks and heated debates are flaring up about what they are and why they have been appearing much more intensely in recent years. What are the reasons for their appearance? Why do they become more numerous in autumn and winter?
Answers
meteorologist Eric Kitas.
Contrails are thin, long white streaks of condensed moisture (droplets or ice crystals). Water vapor condensation is a natural phenomenon caused by the very low temperatures (usually below -40°C) that prevail at the high altitudes where aircraft fly. Tiny particles from the engine, known as condensation nuclei, act as starting points for condensation, leaving behind thin trails of ice crystals.
The length of time that condensation trails are visible depends on the humidity observed at flight altitude:
at
low humidity
a natural process of sublimation occurs, in which a substance passes from a solid state to a gaseous state, bypassing the liquid phase. In a dry atmosphere, ice crystals sublimate and become invisible, causing the thin white lines to dissolve very quickly as the aircraft moves.
high humidity
the ice crystals persist, causing the lines left by aircraft to remain in the sky for several hours and can sometimes "propagate" into cirrus clouds.
“The frequency of contrails has certainly increased in recent years due to the continued increase in flights around the world, which has led to an increase in the number of passenger and commercial aircraft crossing our airspace,” explains Eric Kitas. — At the same time, planes now fly much higher and have more powerful engines that produce more water vapor.
But why are contrails in the skies over Cyprus more common and more intense mainly in autumn and to a lesser extent in winter? This can also be explained from a meteorological point of view.
During the autumn months, the upper troposphere begins to cool significantly as winter approaches, while the waters of the Mediterranean Sea retain much of the summer heat, leading to increased evaporation and higher moisture content in air masses near the earth's surface.
This, combined with the changing weather conditions of autumn, creates unstable atmospheric conditions and areas of high humidity in the upper troposphere, leading to more frequent and intense formation of contrails. In autumn, more often than usual, two criteria necessary for the appearance of contrails are met:
1)
very low temperatures in the upper troposphere,
2)
increased humidity level.
During the summer months, the Mediterranean region is dominated by warmer air masses, with the result that the upper troposphere often lacks the temperature required to form persistent contrails and tends to be limited in number compared to autumn and winter. In spring, temperatures in the upper troposphere may be low, but humidity begins to decline, with the frequency of condensation trails being higher than in summer, but at the same time lower than in autumn and winter.
— Based on the above, no, in our region no one sprays to prevent rain. Traces of condensation have been observed and will continue to be observed without affecting weather conditions, says the Cypriot meteorologist.
