Atmospheric layers

Define troposphere

Lowest layer of the atmosphere where temperature decreases with height/altitude

Define stratosphere

Next layer in the atmosphere after the troposphere, temperature increases with altitude (inversion)

Define mesosphere

Temperature decreases with altitude

Define thermosphere

Temperature increases with altitude

Define ionosphere

Layer in the atmosphere defined by electrical properties and interaction with the solar wind

Define exosphere

Temperature decreases with altitude

Key features of the troposphere (7)

- Temperature decreases with altitude

- Up to 11km

- Average -56.5°C

- Has 75% of the atmosphere's mass

- Warmed from surface by terrestrial radiation

- Components constantly moving, composition keeps changing (behaviour and weather)

- Mainly advection but also conduction and convection

Key features of the stratosphere (5)

- Temperature increases with altitude (to 0°C)

- 11km to 50km

- 21% of the atmosphere's mass

- Not much cloud or turbulence

- Has 90% of atmospheric ozone

Key features of the mesosphere (5)

- Temperature decreases with altitude (-90°C)

- 50km to 90km (Kaman line)

- Extremely low density

- Atmospheric pressure <0.01hPa - 1hPa

- Contains noctilucent clouds

Key features of the thermosphere (4)

- Temperature increases with altitude

- 500km

- Hottest atmospheric layer (2000°C)

- All energy into only a few particles

Key features of the ionosphere (6)

- From mesosphere to exosphere

- Not defined by temperature

- Layer reflects radio waves

- Constantly changing

- Define by electrical properties as solar winds interact with atmosphere

- Causes aurora

Key features of the exosphere (2)

- Temperature decreases with altitude

- Upper limit indeterminate

Define tropopause

Isothermal/transition layer between the troposphere and stratosphere

What is the idealised global tropopause?

- Equator warmer, poles colder

- Thermal expansion = tropopause higher at equator, lower at poles

- Average height 36,090ft

- Equator = 56,000ft, -75°C (65,000ft in summer)

- Poles = 26,000ft, -48°C

- Sub-tropical jet at 40,000ft 30°N/S

- Polar frontal jet stream at 60°N/S

- Slopes gently downward

What causes breaks in the tropopause?

- Areas of mass vertical ascent or subsidence of air in areas between the atmospheric circulation cells

- Surface temperatures cause significant horizontal variations of temperature at altitude (high altitude pressure gradients)

- Breaks disrupt isothermal barrier, large volumes of cold/warm air are brought in

How does temperature change the vertical dimensions of the troposphere?

Increasing surface temperature will increase tropopause altitude

How does pressure change the vertical dimensions of the troposphere?

Increasing pressure will decrease tropopause altitude

How does latitude change the vertical dimensions of the troposphere?

Increasing latitude will decrease the tropopause altitude

How do seasons change the vertical dimensions of the troposphere?

In summer, height will increase. In winter, height will decrease

Why is their generally no cloud or turbulence in the stratosphere?

- Not enough water vapour or aerosols

- These are critical for cloud formation

- They must get past the troposphere stuff and avoid cloud formation there before reaching the stratosphere

- No turbulence (vertical mixing/agitation of air)

- Inversion (stable) layer

Define Nacreous clouds

- Rare stratospheric cloud

- Winter

- 15-25km

- At night (sunsets, refraction of light, illuminating then)

- Mainly ice crystals, supercooled water droplets

What are supercooled water droplets?

Liquid water in temperatures when they should be frozen (below 0°C) but there is no nuclei

What is spontaneous glaciation?

At -40°C, water can't exist in liquid below this temperature

What are noctilucent clouds?

- Rare mesospheric cloud

- 75-85km

- High latitudes 50-65°N/S

- From ice/space debris

- Summer

- Illuminated by sun below horizon

- Refract energy and prevents energy from reaching the earth so it cools

What happens during the ionisation process?

In the region of the atmosphere where the earth's magnetic field and solar wind interact. Interactions strip electrons away from atoms and molecules which form charged particles called ions