Lecture 3 Flashcards
Atmospheric Pressure
The pressure due to weight exerted by the overhead atmosphere.
W=mg P=F/A. F=ma
Barometric Law
Describes the vertical pressure profile of the atmosphere.
Pz = Pe^(-mg/RT) Z
If T is constant P=Pe(-Z/H)
Scale Height
Increase in altitude over which the density & pressure drop by a factor of 1/e.
H=RT/mg
Density & altitude
P= Mair p/RT
Escape Velocity (Ve)
The velocity at which the kinetic energy of a molecule is sufficient to escape the earth’s gravitational field
Vmp=SQRT (2RT/M)
Vrms=SQRT (3RT/M) is Average velocity
Relative humidity
Amount of water vapour in the air relative to the amount needed to saturate the air
RH = actual vapour pressure/saturated vapour pressure
Dew Point
The temperature of air must be cooled for the given amount of water to saturate
What is the temperature of the atmosphere governed by?
- Absorption of energy received by the sun
- Heat production in the interior of earth
- Loss of energy by emission from the earth acting as a blackbody
Lapse Rate
Change in temperature with change in altitude
Troposphere Temp Profile
Why does the temperature decrease as we go higher?
1) Surface of earth absorbs energy from the sun
2) Convection heats up the air near the surface, as it rises it cools due to adiabatic expansion
3) IR radiation is stronger near surface
Stratosphere Temp Profile
Why does temperature increase as we go higher?
1) Large concentration of ozone molecules, ozone absorbs radiation
2) Heating of O3 out weighs cooling process due to larger distance from surface
Mesosphere Temp Profile
Why does temperature decrease as we go higher?
1) Not enough O2 to form O3
2)Too high to receive IR from earth
3) Solar radiation is mainly received by molecules in thermosphere
Thermosphere Temp Profile
Why does temperature increase as we go higher?
1) Higher altitude is closer to the sun
2) Thin atmosphere and high energy (short wavelength) solar radiation
Why are most ions formed in the Ionosphere in Thermosphere
1) High energy photons not shielded
2) High energy photons break molecules into ions
3) atmosphere is thin
