from The American Heritage® Dictionary of the English Language, 4th Edition
- n. An atmospheric area about 80 kilometers (50 miles) above the earth's surface, forming the upper boundary of the mesosphere.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. In the atmosphere, the boundary between the mesosphere and the ionosphere. It is the atmospheric boundary where the temperature reaches its minimum value.
Sorry, no etymologies found.
At the top of the mesosphere is another transition zone known as the mesopause.
What is the volume of air in a 5×5 degree grid (say 0-5 lat 0-5 long) that goes up ~80 km (guessing the below stops around the mesopause boundry and doesn’t count all the way the full 10,000)