We need to remember that most of our civilian flying activity takes place in the Troposphere. Let us now understand about the Troposphere and Tropopause. In our previous post, we had gained an overall understanding of Layers of the Atmosphere.
TROPOSPHERE AND TROPOPAUSE
The lowest layer of the atmosphere or the layer which is closest to the earth’s surface is called the troposphere. The main characteristic of this layer is the decrease in temperature with height. The level where the temperature no longer decreases with height, defines the upper limit of the Troposphere.
This upper boundary is called the Tropopause where the temperature remains constant with increase in altitude. The average height of tropopause is taken as 11 kilometres, which is found at about 45 degrees latitude. However, the height of the tropopause is not constant across the earth.
EQUATORIAL TROPOPAUSE
Over the equator, air expands due to the higher temperatures which results in higher level of the Tropopause. Therefore, in the equatorial regions, tropopause is found at approximately 16 kilometres height with an average temperature of -70 degrees. This is called as the Equatorial Tropopause.
POLAR TROPOPAUSE
Over the poles, air column contrats due to lower temperatures, resulting in a lower height of the tropopause. In the polar regions, the tropopause is found at about 8 kilometres with a temperature of -50 degrees. This called as the Polar Tropopause.
TEMPERATURE AT TROPOPAUSE
You can see that the temperature of tropopause is lower at the equator as compared to the poles. This is the reverse of what happens at the surface, where the surface temperature is lower at the poles as compared to the equator.
This is because the height of tropopause is more at the equator than at the poles. We can say that the height of tropopause reduces with latitude, while the temperature of tropopause increases with latitude.
The height of tropopause is important for pilots because you can find the presence of Jet Streams and Clear Air Turbulence (CAT) near the tropopause.
ISOTHERMAL AND INVERSION
Normally, the temperature falls with height in the troposphere. However, in certain places you may find that the temperature may remain constant with height, resulting in an Isothermal layer. In certain other places you may find that the temperature increases with height, resulting in an Inversion layer.
Understanding about the troposphere and troposphere is important for pilots, because most of the passenger aircraft fly in the troposphere. In addition, most of the weather phenomena are also found only in the troposphere.
The tropopause signifies the start of a marked temperature inversion. This effectively limits the vertical movement of air and clouds within our atmosphere. It’s useful to know then, that the tropopause usually signifies the limit of cloud development.
In this lesson, we hadve learnt about the Troposphere and Tropopause in detail. In the next lesson, we shall understand about the Variations in the Tropopause.