The layered atmosphere
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The Layered Atmosphere. The Earth's atmosphere contains several different layers that can be defined according to air temperature. Troposphere. According to temperature, the atmosphere contains four different layers ( Figure 7b-1 ). The first layer is called the troposphere .

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The layered atmosphere

The Layered Atmosphere

The Earth's atmosphere contains several different layers that can be defined according to air temperature


  • According to temperature, the atmosphere contains four different layers (Figure 7b-1). The first layer is called the troposphere.

  • The depth of this layer varies from about 8 to 16 kilometers.

  • Greatest depths occur at the tropics where warm temperatures causes vertical expansion of the lower atmosphere. From the tropics to the Earth's polar regions the troposphere becomes gradually thinner. The depth of this layer at the poles is roughly half as thick when compared to the tropics.

  • Average depth of the troposphere is approximately 11 kilometers as displayed in Figure 7b-1


  • Above the tropopause is the stratosphere.

  • This layer extends from an average altitude of 11 to 50 kilometers above the Earth's surface.

  • This stratosphere contains about 19.9 % of the total mass found in the atmosphere. Very little weather occurs in the stratosphere. Occasionally, the top portions of thunderstorms breach this layer.

  • The lower portion of the stratosphere is also infuenced by the polar jet stream and subtropical jet stream. In the first 9 kilometers of the stratosphere, temperature remains constant with height.


  • A zone with constant temperature in the atmosphere is called an isothermal layer.

  • From an altitude of 20 to 50 kilometers, temperature increases with an increase in altitude. The higher temperatures found in this region of the stratosphere occurs because of a localized concentration of ozone gas molecules.

  • These molecules absorb ultraviolet sunlight creating heat energy that warms the stratosphere. Ozone is primarily found in the atmosphere at varying concentrations between the altitudes of 10 to 50 kilometers.

  • This layer of ozone is also called the ozone layer . The ozone layer is important to organisms at the Earth's surface as it protects them from the harmful effects of the sun's ultraviolet radiation. Without the ozone layer life could not exist on the Earth's surface.

Stratopause mesosphere
Stratopause & Mesosphere

  • Separating the mesosphere from the stratosphere is transition zone called the stratopause.

  • In the mesosphere, the atmosphere reaches its coldest temperatures (about -90° Celsius) at a height of approximately 80 kilometers.

  • At the top of the mesosphere is another transition zone known as the mesopause.


  • The last atmospheric layer, as defined by vertical temperature change, has an altitude greater than 80 kilometers, and is called the thermosphere.

  • The thermosphere is the hottest layer in the atmosphere.

  • Heat is generated from the absorption of solar radiation by oxygen molecules.

  • Temperatures in this layer can reach 1300 to 1800° Celsius.

SUN +100

-31 units (Albedo)

Reflected back to space

Energy absorbed in Stratosphere +3 units






Energy absorbed in Troposphere

+18 units

( gases ,dust)



+3 units



+25 direct

Total energy absorbed at surface = +45 units

Energy radiated to space –Total = 69 units

Energy from Long wave radiation

= 46 units

Non radiative exchanges = 23 units


-3 units of UV from ozone layer

-21 units from the atmosphere heat input

-14 units from the greenhouse effect

-8 units of direct heat loss from the earth’s surface

Energy gained and lost by the greenhouse effect: Total –14 units

Downward radiation

+96 units

Long wave radiation: -110 units

Non Radiative exchanges units

Convective (turbulent) transfer

- 4 units

Latent heat transfer (evaporation)

-19 units

90 unitso N

40o N


Equator 0o

40o S

90o S

Polar units








Diagram showing the Tricellular Model





Origin units

Maturity units

Occlusion units

Air mass types
Air-mass types

  • There are four main types of air mass:

  • Tropical continental (Tc)

  • Tropical maritime (Tm)

  • Polar continental (Pc)

  • Polar maritime (Pm)

  • And two further sub-divisions:

  • Arctic maritime (Am)

  • Returning polar maritime (rPm)

Energy lost to Space

High Sun 13%

Low Sun


Greenhouse gas

Cloud Type

Long Wave Radiation

Net Radiation Balance


Latent energy

Reflection from ground. Albedo

Surface Absorption of energy

Problems of ice
Problems of Ice protect against radiation frosts, where cold air settles near the surface