Question ID: 500314

[Era]

An aircraft is flying from south to north, above the west east blowing Polar front jet stream, at FL 400 in the Southern Hemisphere. What change, if any, in temperature will be experienced?

Answers available:

It stays the same.
It increases
It decreases - correct answer
It decreases and then increases

can anyone help me to understand the answer.

[JJ Jones]

Here's a diagram of the Southern Hemisphere Polar Front and the West to East Jetstream associated with it. The temperatures are for illustration purposes but you can see that the temperature at the higher tropopause in the warmer sub tropical air is lower than the temperature above the tropopause in the colder polar air. On either side of the jetstream core the temperatures are about the same.
Therefore if flying above the jetstream core from South to North (in the direction of the arrow) the temperature will decrease.

Hope this helps

[tedwood]

Dragging this one back up, but I selected 'Decreases' in the question practise but it came back as wrong and the correct answer is 'decrease then increase'.

Is this an error? If not, can anyone explain why it would then increase? The question explanation doesn't discuss a later increase, only the initial decrease due to higher tropopause?

Thanks
Ed