What causes the temperature outside an aircraft (eg. passenger jet or military transport) to vary while in level cruising flight? And how much does it vary? Are there any records of air temperature during flight that you know of?

I ask because the US 1976 standard atmosphere specifies a uniform temperature throughout the stratosphere that is not realistic.

How much variation at altitude would be expected from: latitude, ocean vs land, summer vs winter, over mountains, monsoon, jet stream, random weather events?

It varies quite a lot.
The coldest I ever saw was -66°, somewhere around Saudi Arabia up in the high 30,000’ range. I’ve also seen +45° near the ground at Riyadh.
Have a look at the standard atmosphere, it’ll show the standard temperature lapse rate. But yes that’s an average and it does very a bit as you go north/south.

Don’t aeroplanes ever record the observed outside air temperature?

mollwollfumble said:

Don’t aeroplanes ever record the observed outside air temperature?

With the old gear I used, no. What we used to do though was give occasional met reports in-flight and that included the OAT. I believe that the modern gear in airliners reports all that back to the base and it’s passed on to Met department.

Spiny Norman said:

mollwollfumble said:

Don’t aeroplanes ever record the observed outside air temperature?

With the old gear I used, no. What we used to do though was give occasional met reports in-flight and that included the OAT. I believe that the modern gear in airliners reports all that back to the base and it’s passed on to Met department.

Thanks SN.

mollwollfumble said:

Don’t aeroplanes ever record the observed outside air temperature?

The airbus I was on from the US to AUS had the outside air temps displayed on the entertainment screen, with altitude, distance..

Not sure how accurate, but it was entertaining.