Lab 2: Vertical Structure of the Atmosphere

Vertical Structure of the Atmosphere

Vertical Structure of the Atmosphere The atmosphere is a compressible “fluid” Molecules are pulled to the earth’s surface by gravity Molecules are most compressed close to the earth’s surface Few molecules exist in earth’s gravitational field beyond 100km Considered arbitrary “top” to the atmosphere 90% of our atmosphere lies below 16km

Vertical Structure of the Atmosphere Within the Atmosphere: Density Decreases as Height Increases Rate: For every 5.6 Km you go up in the atmosphere (ascend), there is ½ the atmospheric mass from when you started Called % above (sea level) If gravitational pull is largest at the surface of the earth, then that too will decrease as you ascend. Connection?

Vertical Structure of the Atmosphere Lab says: “We can assume that 100% of the atmospheric mass lies above sea level and exerts a pressure of approximately 1000 millibars (mb) Same rate applies as “% Above”. Every 5.6 km, half the pressure exists

Vertical Structure of the Atmosphere Partial Pressure of Gas = Total Pressure (as determined by our graph) X Percentage of Gas in the Atmosphere Ex: 1000mb x .78 (percent of Nitrogen) = 780 mb

Vertical Structure of the Atmosphere

Vertical Structure of the Atmosphere Lapse rate – the rate at which temperature changes with height Describes the vertical temperature structure of the troposphere.

Vertical Structure of the Atmosphere Pressure density AND temperature decrease with altitude ↑altitude = ↓air pressure & temperature 1km↑ in altitude = ↓ 6.5°C in air temperature

Vertical Structure of the Atmosphere Troposphere: where most of the weather occurs Temperature decreases as height increases Tropopause: Point between Troposphere and Stratosphere where there is no change in temperature

Vertical Structure of the Atmosphere Tropospheric Lapse Rate: takes an average* Average air temperature at the surface of the earth is 15°C Temperature decreases by 6.5°C per kilometer until 11,000 km Why does it stop? Tropopause

Vertical Structure of the Atmosphere Location of Tropopause varies with season & latitude: colder air has a higher density and lowers the height Thickness depends on high temperature & thermal mixing Highest in the tropics

Vertical Structure of the Atmosphere Ozone warms quickly in the stratosphere Absorbs heat from solar radiation and emits heat (perhaps stabilizing the decrease in the troposphere and increase in the stratosphere) Stratosphere does not warm at the same rate (unlike the troposphere which cools at the same rate) This is due to the ozone layer Ozone like urban heat island Radiation heating