| Term: | Polar night jet stream |
| Definition: | Westerly jet stream of maximum intensity near the stratopause, in the middle and subpolar latitudes of the winter hemisphere, caused by prolonged radiative cooling of the air in high latitudes during this season. |
| Term: | Polar night jet stream |
| Definition: | A core of strong westerly winds that develop during autumn and winter in the upper stratosphere and mesosphere near the boundary of the polar night. Radiative cooling in the polar night appears to maintain the required baroclinicity. |