| the portion of the atmosphere above the troposphere. |
| upper atmosphere n. The part of the atmosphere above the troposphere. |
| upper atmosphere
The part of the atmosphere above the troposphere. The upper atmosphere includes the mesosphere, the ionosphere, the thermosphere, and the exosphere. Temperatures in the upper atmosphere decrease with increasing altitude except in the thermosphere, where temperatures increase significantly with altitude, because the few molecules present receive intense solar radiation. |
