ADIABATIC LAPSE RATE - dT/dz - drop in temperature of a blob of air as it rises without gaining or losing energy.
dT/dz = -g/cp
g= gravitational acceleration cp = Specific Heat Capacity at Constant Pressure
cp = squiggle R / M
M = mean molecular mass =<amu> 0.001 - e.g. air = 29 kg / mol
R = gas constant = 8.31 J K^-1 mol^-1
squiggle = 5/2 for monoatomic gas, = 7/2 for diatomic gas, = 9/2 for triatomic gas
UNITS: cp - (kg m^2 s^-2 K^-1 mol^-1 )/(kg mol^-1) = m^2 s^-2 K^-1
dT/dz = g/cp - m s^-2 /(m^2 s^-2 K^-1) = K m^-1
What's cp for E, V, M? What's dT/dz for Earth, Venus Mars?
m2 s-2 K-1
K / km
|V||CO2||44 x 0.001||850||8.87||10.4|
|E||O2 , N2||29 x 0.001||1003||9.81||9.8|
|M||CO2||44 x 0.001||850||3.71||4.4|
So, Earth and Venus about the same - down in the troposphere - but at Mars the adiabatic temperature profile drops off more slowly with height.
- - - - - = adiabatic lapse rate, White line = actual lapse rate
- if cools faster than adiabatic - stable (cool air sinks)
- if cools slower than than adiabatic - unstable (warm air rises)
For example - here are data from Mars... A = adiabatic, C = condensation of CO2
Heating at the equator - cooling at the poles
WHY less energy flux on Venus? Higher albedo (0.6 instead of 0.4)
WHY the coriolis force? What is the cause? Conservation of angular momentum.
Here is a map of surface winds - not the narrow strips and the the enormous effect of land masses. And seasons.
Below is Fig 4.5 from G&W - note the jet streams - and their changes with seasons - left and right.
An effect of the rapid rotation on Earth is to produce the strong waves in the mid-high latitudes - producing cyclones (L) that hit the west of Europe and US (nasty weather in Britain and coasts of Oregan and Washington states) ...and some anti-cyclones (H). Fig 4-18
Fig 4-16 shows the effect of coriolis forces - they tend to balance the pressure gradient forces leading to circular winds - cyclonic winds anticlockwise and anti-cyclonic clockwise (opposite in southern hemisphere).
Remember the calculations from homework about the latent heat of vaporization and condensation of water? Although the total amount of water in the atmosphere is small, the effects of latent heat on the dynamics can be substantial. Furthermore, the hydrological cycle is of huge planetary importance.