Lab 2: Vertical Structure of the Atmosphere

1. Lab 2:Vertical Structure of the Atmosphere

2. Vertical Structure of the Atmosphere

3. 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

4. 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?

5. 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

6. 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

8. Vertical Structure of the Atmosphere

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

10. 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

11. 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

12. 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

13. 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

14. 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