That portion of the atmosphere from Earth's surface to the stratosphere; that is, the lowest 10 to 20 km of the atmosphere. The troposphere is characterized by decreasing temperature with height, appreciable vertical wind motion, appreciable water vapor content, and weather. Compare to stratosphere. Dynamically, the troposphere can be divided into the following layers: planetary boundary layer, which includes both the surface boundary layer and the Ekman layer, and the free atmosphere. See free atmosphere, Ekman layer, planetary boundary layer, and surface boundary layer.