- the portion of the atmosphere above the troposphere.
Compare upper air.
Origin of upper atmosphere
First recorded in 1890–95
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
- meteorol that part of the atmosphere above the troposphere
- 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.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.