# Contrails and Their Dependence on Meteorological Situations
###### Abstract  
Contrails created by aircraft are a very hot topic today because they contribute to the warming of the atmosphere. Air traffic density is very high, and current forecasts predict a further significant increase. Increased air traffic volume is associated with an increased occurrence of contrails and induced cirrus clouds. The scientific level of contrails and their impact on the Earth's climate is surprisingly low. The scientific studies published so far are mainly based on global models, in situ measurements, and satellite observations of contrails. The research is based on observations of contrails in flight paths in the vicinity of Dscin and Prague, and the collection of flight and meteorological data. It focused on the influence of the meteorological situation on the formation of persistent contrails. The collected data on contrails and meteorological variables were statistically processed using machine learning methods for classification models. Several models were developed to predict and simulate the properties of contrails as a function of given air traffic and meteorological conditions. The Random Forests model produced the best results. Dependencies between meteorological conditions, formation, and contrail lifetime were found. The aim of the study was to identify the possibility of using available meteorological data to predict persistent contrails. Keywords:contrail; induced cirrus clouds; Schmidt-Appleman criterion; meteorological data; aerological measurements; prediction; classification models +
Footnote †: journal: Medical  
The duration of the contrail depends mainly on the value of the partial pressure of water vapor in the surrounding air. If the resulting ice particles are in an environment during the mixing process in which the water vapor partial pressure value is lower than the saturation value relative to the ice, the ice particles will sublimate, and the contrail will be short-lived. As the relative humidity of the environment relative to the ice increases, the sublimation process slows down. If the value of the partial pressure of water vapor around the ice particles exceeds the saturation value relative to the ice, not only will the ice particles not sublimate, but they may continue to grow via the deposition of water vapor from the surrounding air as long as the air around the ice particle is supersaturated relative to the ice [7]. Thus, the occurrence of natural cirrus, persistent contrails, and contrail cirrus is closely related to the occurrence of sufficiently cold supersaturated regions relative to ice (CISSR). This is usually defined as a region with relative humidity with respect to ice (RHi) > 100% and a temperature below 233 K and typically located near the tropopause [8; 9]. CISSR can be horizontally extensive in the order of hundreds of km, but they are also very shallow, with a vertical extent of one flight level. The occurrence of CISSR is mainly related to outward air motions, typically in regions of frontal systems, storm system trajectories, in the Northern Hemisphere at mid-latitudes in areas south of Jetstream trajectories, in anticyclonic flow near ridges of higher air pressure, and in warm cyclone transmission belts [10; 11]. Short-lived contrails have virtually no effect on the Earth's energy balance but induced cloud cover have, because of their long persistence and extensive spatial coverage. It has a significant effect that can be both warming and cooling, with the positive effect dominating globally [7]. Long-lived contrails and induced cirrus clouds mainly affect the long-wave radiation and, therefore, mostly cause positive radiative forcing, which tends to warm the atmosphere [9]. Recently, there has been more interest in contrails because of their environmental impact, which consists of an increase in induced cirrus clouds and the consequent effect on atmospheric temperature. Until recently, legislation did not address the formation and occurrence of contrails and their effect on the environment and climate.