Planes fly in the second layer of the atmosphere called the stratosphere. This layer is placed above the troposphere and below the mesosphere. The layer got its name because it is stratified in temperature. This means that the warmer layers are higher up while the colder layers are closer to our planet.
The reason the temperature increases with height is because of the ozone layer. It absorbs the Sun’s ultraviolet radiation. This makes the stratosphere opposite of the troposphere, the layer where humans live. In that layer, the temperature decreases the higher we go.
The stratosphere is separated from the troposphere by a layer called the tropopause. This is the place where the temperature inversion starts to happen. The height of the stratosphere changes depending on the part of the planet. It can be 66,000 feet high near the equator, but it gets significantly lower when we approach the poles. There, the stratosphere begins at heights of just 23,000 feet.
The temperatures in the stratosphere vary greatly but are always much colder than the surface of our planet. The temperature near the tropopause is always around -51°C, and it rises to around -15°C when we approach the mesosphere. However, the temperatures in this layer are known to vary greatly depending on the season we are in. During the winter, they can get extremely low. The winds blowing in the stratosphere are much stronger than those in the troposphere. They can reach speeds of up to 130 miles per hour.
The Ozone Layer
The stratosphere is the layer of the atmosphere where we can find the ozone layer. The ozone layer forms when molecular oxygen absorbs the extremely high amounts of energy coming from the Sun. This happens at wavelengths that are shorter than 240 nanometers. When the oxygen molecules split, they produce radicals that combine with molecular oxygen and then form ozone.
Ozone gets photolyzed faster than molecular oxygen. It also has a stronger absorption because of the more intense solar emission at its wavelengths. The ozone layer is also known as the ozone shield, and it absorbs the majority of the ultraviolet radiation coming from the Sun. We mainly find the ozone layer in the lower parts of the stratosphere, although this varies depending on the geographical location.
Aircraft In The Stratosphere
The majority of commercial airlines fly at heights between 30,000 and 39,000 feet, which makes up the lower parts of the stratosphere. These parts are chosen because flying through them is optimal for the consumption of fuel. The low temperatures combined with low air density are responsible for this. They allow the planes to fly faster while also maintaining the necessary lift.
Due to the constant temperature in the tropopause and the stratosphere, there is less chance of turbulence to occur there. The turbulence that happens when we fly somewhere in commercial flights is caused by local wind shears and small variations that happen in the jet stream. However, the dangers of thunderstorms may cause stronger turbulence in these parts.