The stratopause is a layer in the Earth's atmosphere which lies above the stratosphere and below the mesosphere. The temperature within the stratopause is influenced by the absorption of ultraviolet (UV) radiation from the sun, which is more intense at the equator than at the poles. In January, the Southern Hemisphere is experiencing summer, and the Northern Hemisphere is in winter.
At the poles, the situation is particularly extreme: the pole tilted away from the sun experiences polar night, a period during which it receives no direct sunlight at all. This contributes to extremely cold temperatures. Conversely, the pole tilted towards the sun experiences polar day and gets continuous sunlight, which, although less intense than at the equator, mitigates the extreme cold to some extent.
Given these dynamics, during January, which is winter in the Northern Hemisphere and summer in the Southern Hemisphere, one would expect the following in terms of coldest temperatures at the stratopause:
a. The North Pole experiences extreme cold due to the lack of sunlight (polar night).
b. 45° N is cold but not as extreme as the pole, as it does receive some amount of sunlight during the day.
c. The equator receives continuous sunlight year-round but is less intensely cold due to the inclination of Earth's axis. Day and night are of almost equal duration throughout the year.
d. The South Pole is experiencing summer conditions with continuous sunlight (polar day), which will cause it to be less cold than the North Pole.
Therefore, the coldest temperature at the stratopause (1 mb) in January is most likely found at:
a. the North Pole
The North Pole is the coldest due to it being winter there with no sunlight reaching it, leading to very cold atmospheric temperatures at all levels, including the stratopause.
