Composition, extent, vertical division

050-01-01Pablo Asensio Martínez2026-04-012 min

Layers of the Atmosphere

Atmosphere Layers

The atmosphere is divided into several layers based on the variation of temperature with altitude:

  1. Troposphere:

    • It is the lowest layer, extending from the surface to the tropopause.
    • It contains approximately 75% of the mass of the atmosphere and 99% of the water vapor.
    • Almost all weather (clouds, precipitation) occurs here.
    • Temperature decreases with height (approx. 2°C/1000 ft or 0.65°C/100m).
    • Dry air composition: 78% Nitrogen, 21% Oxygen, 1% others (Argon, CO2, etc.). Water vapor varies between 0% and 5%.

  2. Stratosphere:

    • Extends from the tropopause to the stratopause (approx. 50 km).
    • Temperature increases with height (thermal inversion) due to the absorption of UV radiation by ozone.
    • It is a very stable layer, with little vertical turbulence, ideal for commercial jet flight in its lower part.

  3. Mesosphere:

    • From the stratopause to the mesopause (approx. 85 km).
    • Temperature decreases with height, reaching the coldest values in the atmosphere.

  4. Thermosphere:

    • From the mesopause to approx. 600 km.
    • Temperature increases drastically.

  5. Exosphere:

    • The outermost layer, transitioning into space.

The Tropopause

It is the boundary between the troposphere and the stratosphere. It is defined as the point where the temperature stops decreasing with height (becomes isothermal or increases).

Tropopause and Jet Streams Cross Section

  • Height Variation: The height of the tropopause is not constant; it varies with latitude and season (surface temperature).
    • Equator: Higher (~16-18 km / 56,000 ft) due to convection and expansion of warm air.
    • Poles: Lower (~8-10 km / 26,000 ft) due to contraction of cold air.
    • Seasons: Higher in summer, lower in winter.
  • Height/Temperature Relationship:
    • High Tropopause (Equator) -> Colder Temperature (approx. -80°C).
    • Low Tropopause (Poles) -> Warmer Temperature (approx. -40°C).

Atmosphere Temperature Profile

  • ISA (International Standard Atmosphere): Assumes a tropopause at 11 km (36,090 ft) with a constant temperature of -56.5°C.
  • Tropopause Breaks: It is not a continuous surface; there are "breaks" where Jet Streams occur and air exchange between the troposphere and stratosphere takes place.

Ozone (O3)

  • Location: 90% is found in the stratosphere (Ozone Layer, between 15-35 km). The remaining 10% is in the troposphere.
  • Function: Absorbs harmful ultraviolet (UV) radiation from the sun, which heats the stratosphere.
  • Hazards for Aviation:
    • Ozone is toxic.
    • On high-altitude flights (jet cruise in the lower stratosphere), the concentration can be dangerous.
    • Symptoms: Irritation of eyes, nose, and throat, chest pain, cough, difficulty breathing.
    • Modern aircraft have catalytic converters to break down ozone before it enters the cabin.

Water Vapor

  • It is the most important gaseous component for meteorology.
  • It is the main engine of weather patterns (energy transport, latent heat).
  • Necessary for the formation of clouds and precipitation.