Page 214 - PPL-engelsk 2025

Meteorology

3.2 The atmosphere, composition and structure

The Earth's atmosphere consists of approximately 78% nitrogen, 21% oxygen,

almost 1% argon, and small amounts of other gases.

From a meteorological perspective, the atmosphere is made up of:

- Dry air

- Water vapor

- Pollution particles

The atmosphere protects life on Earth in several ways. It absorbs cosmic

radiation from space (small particles burn up in the atmosphere before they

reach the Earth's surface), and the ozone layer reduces harmful solar radiation

(UV). The atmosphere extends far into space and consists of various layers.

3.2.1 The Troposphere

Most weather phenomena occur in the lower part of the atmosphere,

specifically in the layer known as the troposphere.

On the next page, you will see a diagram extending from the Earth's surface to

700 km into space. Of this, the lowest 8-16 km constitutes the troposphere, the

part of the atmosphere where we are located.

An important component of the troposphere is water. 99% of all water is found

within 10 km (30,000 feet) of the Earth's surface. Half of it is found below 2 km

(6,000 feet). The reason water is not found at higher altitudes is due to low

temperatures.

Flight Theory PPL(A)(UL)/LAPL Henning Andersen, Midtjysk Flyveskole© 2025 214