How does air temperture aloft vary with latitude ?
 

Many decades ago when I was an air cadet, I think I was taught that air temperature aloft typically reduces by c. 1C for each 1000ft of altitude.

Logically, if this were true, it should mean that an aircraft flying a Great Circle route in July at a constant altitude of 38,000ft from overhead the North Pole (-50C at ground level ?) to overhead Aziziya in Libya (+50C at ground level ?) would experience an outside air temperature rising from -88C to +11C.

I'm sure this can't be right, but would love to hear the correct answer from a suitably qualified person, thanks :)

I was always taught that the typical temperature drop was about 2 degrees per thousand.

Dry adiabatic lapse rate, 3 degrees C per 1000 ft. Saturated adiabatic lapse rate, 2 degrees C per 1000 ft.

Make that 1.5C for the saturated.
Adiabatic lapse rate is not the same as the observed lapse rate, that is, the temperature drop with altitude ''on the day''.

https://en.wikipedia.org/wiki/Intern...ard_Atmosphere

YMMV. :O

And you aren't going to get -50C at the North Pole in July. You could actually get temps closer to +5 to -5C. -50 would be more high winter temps.

Don't forget the Tropopause.
 

I think the environmental lapse rate is generally quoted as being approximately 2 Celsius per thousand feet, as per DR and Tarqs posts. However don't forget (?) the Tropopause, the point at which the temperature stops dropping or sometimes even begins to start rising again as you continue to climb, and which tends to be at lower altitudes over the poles than over the equator..it can certainly be well below 38,000 feet at higher latitudes, indeed down in the 20 thousands of feet is quite common. As a result linear extrapolation of temperature might work up to 38000 feet at Equatorial Latitudes where there's usually a very high "Trop", it won't be valid near the Poles.

In the real world I can't recall seeing much colder than -65 to -75'ish celsius.....that's over Siberia cruising in the mid 30 thousands of feet.

BTW as far as I recall it the wet/dry diabetic lapse rates (1.5 and 3 degrees per thousand) are much more tied in with stability/instability and apply to ascending masses of air, rather than the linear drop in air temperature as you yourself ascend through the atmosphere.

Tropopause
 

Your theory works to the tropopause only...over the pole it can be around 26,000ft and equator 40,000+....
Then iirc the tempr lapse rate decreases or remains constant.

The effect of the tropopause is that the upper levels over the equator can get colder than the upper levels over the poles.

Just to add some meat to the bones and for the benefit of the OP I've looked back at some charts/data for Sunday AM.

Tropause "heights":

Over Sudan, equatorial air, the Tropopause was forecast at 55000 feet, Over Eastern Europe, in air of polar origin the tropopause was down at around 25000 feet.

Crusie altitude temperatures:

Over northern Africa at an altitude of 39000 feet it was forecast to be -53 celsius.

Over Lyon at 37000 feet the temperature was forecast to be -55 celsius.