Vertical structure - The atmosphere

Vertical structure - The atmosphere

1. Atmosphere can be divided up into well-marked horizontal layers mainly based upon temperature.

   • Troposphere
   • Stratosphere
   • Mesosphere
   • Thermosphere

2. Troposphere

   • Lowest layer, where turbulence and weather most marked
   • contains virtually all water vapour and 75% molecular mass of the atmosphere
   • general decrease of temp at a rate of 6.5 degrees Celsius/km
   • Tropopause - temp inversion layer which acts like a lid on weather and the troposphere

3. Stratosphere

   • Second layer, 50km troposphere upwards.
   • contains much of the Ozone
   • maximum temperature occurs at the stratopause (may exceed 0 degrees Celsius)
     • Temp increase due to the low density of air at this height.

4. Mesosphere

   • above the stratopause average temps increase to about -90 degrees Celsius - rise again after 80 km due to the Ozone and Oxygen molecules absorbing radiation
     • This temp inversion is called the mesopause
   • Pressure low here decreasing from 1 mb at 50 km to 0.01 mb at 90km (surface pressure = 1000 mb)

5. Thermosphere

   • Atmospheric densities very low
   • Molecular and atomic oxygen absorb solar radiation at this point.