Monday, April 22, 2024

The Tropospheric Lapse Rate Simply Derived From Calorimetry



I received a comment about warming of the troposphere, on "The True and Simple Physics Being Denied" post from 2021, and, upon consideration, my response, which I explained years ago, deserves to be seen again, by all:

"Have you cosidered that gravitation continuosly press atmospheric gases. That makes atmosphere warmer than it should be. That is lapse rate."

You do not understand what causes the "lapse rate" temperature gradient in the troposphere, which depends upon the pressure gradient, and you confuse "compressed" (as an unchanging condition) with "pressing" (as a continuing action). The troposphere has an equilibrium -- non-changing -- pressure and temperature condition, which is experimentally identifiable as the hydrostatic condition, where the pressure at any level is just the weight of the atmosphere above that level.

This imposes a quite simple physics upon the lower atmosphere, going all the way back to the introductory physics of calorimetry (the measurement of heat energy by the work it performs).

In the hydrostatic condition, one can investigate how the temperature must vary as a function of altitude, by looking at the potential energy of a small volume of air at a given level, and how it changes with a small change in altitude. The potential energy is just ρgh, where ρ is the mass per unit volume, g is the gravitational acceleration, and h is the altitude. Just above that small element of air is another, whose potential energy is ρg(h+Δh). The difference in potential energy, ρg Δh, is by the basic calorimetry equation, -ρc ΔT (a positive change in altitude gives a negative change in temperature), with c the effective specific heat of the air. So ΔT/Δh = -g/c. So the temperature gradient, or lapse rate, is just a constant, -g/c. There is no continuous compressing of the atmosphere, it has already been compressed to its equilibrium, hydrostatic condition.

I explained this simple physics years ago. Unfortunately, the "global warming" non-debate -- actually part of a WAR, that I call "The War of the Insane Left" -- leaves non-physicists high and dry and without a correct physics leg to stand on. However, I do not take political or ideological comments, so no more here on that subject.

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