When I was a little boy, my guardian would point to the sky, showing me those white trails, and say, “Look, it’s a jet!” I used to think they were fighter jets, and I was fascinated by how straight they were and how they didn’t disappear easily. Later on, I discovered that these trails were made by commercial planes flying at very high altitudes. I learned that these trails left by planes are called contrails, and they’re not smoke coming from the plane’s engines or wingtips. So, here’s something you might want to know about those white trails left by planes, also known as condensation trails or contrails.
Contrails are actually a type of cloud, and their formation is a result of the temperature difference between the hot, humid air around a plane’s engine and the low temperatures outside the aircraft. In this article, we’ll explore the science behind contrails, how they form, and why they can sometimes linger in the sky for a long time.
The Science of Contrails
Contrails form mainly at high altitudes where the atmosphere has much lower vapor pressure and temperature compared to the exhaust gas from a plane’s working engine. The exhaust contains not only water vapor but also carbon dioxide, oxides of sulfur and nitrogen, unburned fuel, metal particles, and soot. These elements provide condensation sites for the water vapor.
When a plane is flying at high altitude, where the temperature is about minus 40 degrees, the vapor condenses, turning into fog or small ice crystals. These crystals evaporate more slowly than regular water, and that’s why those white trails remain in the sky for a long time.
Factors Affecting Contrail Formation
The appearance of contrails depends on several factors, including the height and composition of the surrounding atmosphere. Here’s how different conditions can affect contrail formation:
Humidity
If a plane flies over a region with dry air, there are no small particles of water in the air, and nothing to freeze outside. In such areas, there may be no contrails at all, or they may be very pale and disappear quickly.
Temperature
The colder it is outside, the longer, thicker, and brighter the white stripes are. In some northern regions where the air temperature reaches minus 50 degrees and below, a contrail can form even during takeoff or landing.
Altitude
Contrails typically don’t form after airplanes and helicopters that fly at low altitudes. The air temperature is not low enough, and water particles simply don’t have time to turn into crystals.
A Common Phenomenon Explained
The mechanism of contrails’ formation is similar to what happens when a cold bottle is left in a hot room. If the temperature difference is high enough, the plastic fogs up, and water droplets form on the bottle. It’s the same thing that happens if you walk through the frost with glasses and then enter a warm room.
Contrails are a common and intriguing phenomenon that many of us observe but might not fully understand. These white trails left by planes are not just beautiful to look at; they tell a story of science and weather conditions. The next time you see those white lines in the sky, you’ll know exactly what’s happening up there.
First love never dies. I fell in love with airplanes and aviation when I was a kid. My dream was to become a pilot, but destiny led me to another path: to be an aviation digital media content creator and a small business owner. My passion for aviation inspires me to bring you quality content through my website and social accounts. Aviation is indeed in my blood and blog!
