Why airplanes taxi

On Feb 10, 9:47 am, Mxsmanic wrote:
So, overall,
the air is always warmest at the surface. There are some anomalies higher in
the atmosphere.

Not always. Not at all always. We frequently get inversions where the
air 1000' feet up is much warmer than that on the surface. Inversions
are very common here, and I would imagine they're common most anywhere
away from the equator. We've had days here, in the winter, where we've
left the ground where the temp is -20°C, and found -18°C at 3000' agl.
Often I find the winds howling at 25 or 30 knots just 200 feet above
the surface, while the wind on the ground is zilch and the temp is 25
degrees colder.
"Always" just doesn't deal with reality. Works on a sim, I
suppose.

Parcels of air that rise in the atmosphere will cool as the pressure in the
atmosphere drops, and this is responsible the adiabatic lapse rate.

If you'd ever studied meteorology (Commercial Pilot
groundschool) you'd know that the temp falls with altitude until we
reach the tropopause. Then it starts rising until we reach the
stratopause, where it starts to fall again through the mesosphere, and
once we reach the thermosphere it rises again and keeps on rising,
though the density is so low that the actual heat content is minimal.
See this:
http://www.ux1.eiu.edu/~cfjps/1400/FIG01_019.JPG

In both cases, the correlation is between temperature and altitude, not
temperature and pressure.

If pressure rises, so does temperature. The air coming down
off the Rockies here rises in temperature as its pressure rises in the
descent. This is part of the chinook phenomenon's equation. The rest
of that equation has to do with condensation of the vapor on the west
side of the mountains, which releases the heat of evaporation back to
the atmosphere so that the air's temperature fall is minimal as the
air is forced upward by the terrain. So when it gets to 3000' on this
side, it's MUCH warmer and drier than it was at 3000' on the west
side. The snow evaporates (sublimates) in that warm, dry air. It
doesn't have a chance to melt.
The atmosphere is much more complex than you think.

Dan