How do greenhouse gases affect the adiabatic lapse rate?

Question

How do greenhouse gases affect the adiabatic lapse rate?

Answer 1

The adiabatic lapse rate would probably never equal

the environmental lapse rate barring the water cycle.

The reason is obvious if I understand the definition

of "environment" correctly. Thus, GHG would be a factor.



Edit:

Considering one model, the environmental lapse rate can be derived by

simply letting the "troposphere" remain effectively impervious to infrared photons.

Hence, energy is transported via GHG collision flux to an effective emission

surface where the aforementioned hidden photons are released into

space. This lapse rate is unequal to the ideal adiabatic lapse rate

derived via thermodynamics although this rate might adjusted by

considering the fact that GHG profile in the atmosphere is not isotropic

which brings to vision another model for me to think about. Hence we may

pretend, so to speak, that energy transport via latent heat is not a

factor.

Answer 2

I'm not sure I entirely understand your question, but the reason the actual lapse rate =/= the adiabatic lapse rate is because of water vapor. GHGs affect the starting temps, but the GH properties of GHGs don't greatly affect the LR itself (to the extent that they don't explain the difference between the dry adiabatic LR and the actual).



I believe the adiabatic lapse rate is a pretty good approximation for dryer regions like the poles, with the small differences being largely due to small amounts of water vapor in the air.



Or maybe I'm missing something?

Answer 3

You can sharpen your pencils on this one, or you can give a qualitative (liberal arts) answer.



And I am most interested in the effect of greenhouse gases other than H₂O.



See: http://en.wikipedia.org/wiki/Troposphere…

4 hours ago



********

Good points Bad Moon, NW Jack and Dana, but the genesis of the question is that



Environmental Lapse rate ≠ Adiabatic Lapse Rate



Ignoring for the moment the water cycle (i.e., wet adiabatic lapse rate), GHG have an effect on the lapse rate so that it is not the adiabatic lapse rate.

Answer 4

The adiabatic lapse rate is a property of gases to cool as they drop in pressure. To the extent that pressure drops as altitude increases, atmospheric gases cool as they gain altitude. "Adiabatic" means no heat being added or taken away using any external source. Thus, the change in temperature represents the amount of work that the gases do on the surrounding gases. The work done is the integral of the change in the product of the pressure and the specific volume of the gas.



To the extent that greenhouse gases tend to be heavier than air, and thus bring up the specific gravity of air, they cause the pressure gradient to be very slightly steeper. Thus, the adiabatic lapse rate increases extremely slightly as CO2 concentration increases, and decreases extremely slightly when CH4 concentration increases.



MW Air = 29

MW CO2 = 44

MW CH4 = 16



Edit:

If you want to ask about the environmental lapse rate, and how greenhouse gases affect it, then the answer depends on the model used. http://en.wikipedia.org/wiki/Climate_models



1) The older models predicted a hot spot in the mid troposphere at 6 km up. In other words, it was expected that this altitude would heat faster than the surface, and faster than the zone above it. http://www.worldclimatereport.com/index.php/2004/07/19/the-data-weigh-in/

That never happened proving that there was something wrong with the original models. http://www.ssmi.com/msu/msu_data_description.html#msu_amsu_time_series



2) Like good scientists, they reworked their models which no longer predicts a hot spot at that altitude in the same sense as the old models. Now, 6 Km is the pivot point. The surface would warm the fastest. The amount of warming expected would decrease as the 6 km altitude is approached. At about 6 Km, the effect will be about neutral, and above 6 Km the atmosphere would cool. http://www.realclimate.org/index.php/archives/2004/12/why-does-the-stratosphere-cool-when-the-troposphere-warms/



The idea is that greenhouse gases capture heat closer to the surface, and convert it to wavelengths that the atmosphere is transparent to. Thus, in theory, the heat tends to have escaped and is no longer being trapped as we ascend in altitude beyond the 6 Km altitude.



All this means that in theory one would expect a greater lapse rate due to a greater temperature drop as one ascends in altitude.



Of course, this is partly an example of curve fitting after the original models that attempted to demonstrate CO2 as the primary cause of global warming failed. That explains the new agreement with the altitude data.

Answer 5

It should decrease the Lapse Rate. Whether it is or not becomes the magic question. Global Warming is at present, a documented Surface expression of warming that must be transferred upward to an ultimate cooling of Absolute Zero in the uppermost atmosphere. A failure to decrease the Lapse Rate would be indicative that there is something terribly wrong with the Temperature Data.

As one AGW proponent (properly) described Global Warming to me, "it is like a bathtub attempting to drain water". The heat must eventually be translated upward, and the rate at which the heat is transferred will manifest as Global Warming at surface.

Answer 6

The increase in water vapor as surface air temperature rises causes a change in the moist-adiabatic lapse rate such that the surface to mid-tropospheric gradient decreases with increasing temperature (i.e. it warms faster aloft).