Chapter 1B: Air Pressure and Density & Vertical Structure of the Atmosphere Flashcards
Explain the concept of air pressure in terms of mass of air above some level.
If more molecules are packed into an air column, the column becomes denser, the air weighs more, and the surface pressure goes up.
On the other hand, when fewer molecules are in the air column, the air weighs less and the surface pressure goes down.
What is the relationship between air pressure and height?
Air pressure decreases exponentially with height
Why does air pressure decrease with increasing altitude?
As altitude increases, there is always less air above you (because more of it is below you).
Why do we feel a pressure change in a train, airplane or car? (ears popping)
This is due to a relatively sudden change in altitude.
What is the relationship between air density and height?
Air density decreases exponentially with height.
What is Avogadro’s law? (ideal gas law)
For any gas at the same temperature and pressure, one mole of gas occupies the same volume.
How do high altitudes affect oxygen levels?
At high altitudes, the air density is low. This means that there will be a lot less O2 available to breathe. (although the proportions of N2 and O2 remain the same).
Describe what the pressure at a certain vertical level would be.
The pressure at a given altitude is equivalent to the weight of the overlying air column per unit area.
(for the atmosphere)
How does pressure vary in water?
Pressure increases with water depth.
What is hydrostatic equilibrium? SLIDE 28
Balance between vertical pressure gradient force and the force of gravity per unit of volume.
Why do pressure and density decrease rapidly with height?
- Pressure decreases approximately exponentially with height because of the hydrostatic balance of the atmosphere.
- Because Density = Pressure /( R’ x Temperature), density also decreases approximately exponentially with height.
If you were suddenly placed at an altitude of 100 km above Earth, would your stomach expand or contract?
Your stomach would expand because the pressure outside your body would be several orders of
magnitude less than the pressure inside your body
