troposphere [%PREMIUM_LINK%] (trō'pə-sfîr', trŏp'ə-) Pronunciation Key |
The lowest and densest region of the Earth's atmosphere, extending from the Earth's surface to the tropopause. The troposphere is characterized by temperatures that decrease with increasing altitude. At the top of this region, temperatures are close to -55°C (-67°F). The weather, major wind systems, and cloud formations occur mostly in the troposphere. See also exosphere, mesosphere, stratosphere, thermosphere., See illustration at atmosphere.