Layer of the atmosphere between 30 and 50 mi (50 and 80 km) in altitude, characterized by decreasing temperatures with increasing altitude.
The region of the atmosphere lying above the stratosphere and extending from the stratopause at about 50 km height to the mesopause at 85â€“95 km. The mesosphere is characterized by decreasing temperature with increasing height, reflecting the decreasing absorption of solar ultraviolet radiation by ozone. Many features of the mesosphere remain poorly understood since in situ measurements are difficult. The region is too high for balloon operations and too low for satellites to orbit. Rockets, while useful, usually travel too rapidly through the region to produce reliable measurements. See atmospheric shell.
The atmospheric shell between about 20 km and about 70 to 80 km, extending from the top of the stratosphere (the stratopause) to the upper temperature minimum that defines the mesopause (the base of the thermosphere).