All the condensation trails they are icy clouds, long lines that sometimes appear when an airplane passes and are caused by the condensation of the water vapor contained in the emissions of the engines. Sometimes other types of contrails are also formed on the tips of the wings, due to the condensation of atmospheric vapors caused by the drop in pressure and temperature that occurs when the aircraft passes, but the latter usually occurs during takeoff and landing. , not during flight at high levels, and they last much less.
For this reason, we are going to dedicate this article to telling you everything you need to know about condensation trails and their characteristics.
Key features
Aircraft engines emit water vapour, carbon dioxide (CO2), trace amounts of nitrogen oxides (NOx), hydrocarbons, carbon monoxide, sulfur gases and soot and metal particles. Of all these gases and particles, water vapor is the only one associated with contrail formation.
To form a large contrail behind an aircraft en route, certain temperature and humidity conditions are necessary to allow the condensation of the water vapor emitted by the engines. Sulfur gases can help because they help form small particles that can act as condensation nuclei, but generally anyway.
There are enough particles in the atmosphere to act as condensation nuclei. The remaining gases and particles emitted by the aircraft engine they do not affect wake formation.
When the gases emitted by the aircraft mix with the surrounding air, they cool rapidly, if there is enough moisture in the atmosphere to cool the mixture. When saturation is reached, the water vapor condenses. The moisture content of the mixture, ie whether it reaches saturation, will depend on the temperature and humidity of the air, as well as the amount of water vapor and the temperature of the aircraft emissions.
How they are formed
Depending on the amount of air and gas expelled, temperature exchange, and moisture content, contrails can become denser, more persistent, and conducive to cloud formation, or otherwise begin to rapidly dissipate.
Naturally, in the atmosphere, especially at high levels, the levels of humidity and air fluctuations give way to the formation of cirrus clouds or cirrus, and sometimes these can be quite similar to condensation trails left behind by an airplane or any type of aircraft. To distinguish them, an analysis of meteorological observations must be carried out and determine at what level of the atmosphere they are found and what is their source of formation.
One of the most common tools to see them in greater detail are satellite images taken from space. Scientific observations have determined that contrails last only a few seconds or minutes when the air in the atmosphere is dry, but when the air is moist, contrails can last longer and expand into wide cirrus clouds, generally the same as about the same natural source
Contrails typically reduce the amount of solar radiation reaching the Earth's surface, thereby increasing the amount of infrared radiation absorbed by the atmosphere, much like cirrus clouds with similar characteristics.
Types of condensation trails
Once a contrail has formed, its evolution depends on atmospheric conditions. So we can see the three types of contrails mentioned in the poster:
- short trails: these are the little white lines we see behind the plane that disappear almost as fast as the plane passes. They occur when the amount of water vapor in the atmosphere is low, and then the ice particles that form the wake quickly return to their gaseous state.
- Persistent contrails that do not propagate: these are long white lines that persist after an aircraft has passed, but do not grow or spread. They occur when atmospheric humidity is high, so contrails do not evaporate (more precisely, they do not sublimate), and they can last for hours.
- Persistent contrails that remain: as the cloud grows, the lines become thicker, wider, and irregular in shape. This happens when the humidity in the atmosphere is very close to the condensation level, water vapor in the atmosphere can easily condense into ice particles in the wake. If there is also some instability and turbulence, the trajectory has an irregular shape. These trails can also be moved by the wind.
Contrail Prediction
The first mention of contrails dates back to the end of World War I, when planes could fly at high altitudes. They are given the conditions of their formation. Until the beginning of World War II, they were considered just a curiosity, but during the war, contrails became a very interesting topic because they could give away the position of an airplane. So, in different countries, they began to investigate the causes and conditions of their formation. In 1953, the American Appleman published the graph that makes it possible to determine whether and at what level contrails will form with knowledge of high-altitude temperature and humidity conditions.
Contrails are possible under these conditions (if there is enough moisture in the surrounding atmosphere) Above the 400hPa level, it corresponds to an altitude of about 7 km. and more and more likely to be at higher levels until it is almost certain (even with 0% humidity in the atmosphere) Above about 280 hPa (points marked in red), that is, slightly above 9 km high.
atmospheric disturbances
Many human activities have harmful effects on the atmosphere, and these lines in the sky are a good example. The gases emitted by aircraft are pollutants that directly and indirectly damage the atmosphere. When the polluting gas combines with the steam, the water droplets in the cloud acidify and the contaminants eventually settle to the surface.
The increase in airlines in recent years has led to an increase in contrails, which of course affects the natural process of exchanging radiation and illumination from the sun with the earth, a condition that causes irregular heating or cooling of the Earth. Earth's surface, in the atmosphere.
I hope that with this information you can learn more about condensation trails, their characteristics and formation.