[mez-uh-sfeer, mes-, mee-zuh-, -suh-] 
| 1. | (in the classification of the earth's atmosphere by chemical properties) the region between the ionosphere and the exosphere, extending from about 250–650 mi. (400–1050 km) above the surface of the earth. |
| 2. | (in the classification of the earth's atmosphere by thermal properties) the region between the stratosphere and the thermosphere, extending from about 20–50 mi. (32–80 km) above the surface of the earth. |
| mes·o·sphere (měz'ə-sfîr', měs'-) n. The portion of the atmosphere from about 30 to 80 kilometers (20 to 50 miles) above the earth's surface, characterized by temperatures that decrease from 10°C to -90°C (50°F to -130°F) with increasing altitude. mes'o·spher'ic (-sfîr'ĭk, -sfěr'-) adj. |
mesosphere
region of the upper atmosphere between about 50 and 80 km (30 and 50 miles) above the surface of the Earth. The base of the mesosphere is defined as the temperature maximum existing at the top of the stratosphere, with the boundary between the two regions usually called the stratopause. The mesosphere extends upward to the next temperature minimum, which defines the base of the thermosphere; the boundary between the two regions is called the mesopause.
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əˌsfɪər
