Chapter 8-Circulation of the Atmosphere 2 Flashcards
height, temperature, composition, boundary
Mesosphere
This layer extends from around 50 km above the Earth’s surface to 85 km. The gases, including the oxygen molecules, continue to become more dense as one descends. As such, temperatures increase as one descends rising to about -15°C near the bottom of this layer.
The gases in the mesosphere are now thick enough to slow down meteors hurtling into the atmosphere, where they burn up, leaving fiery trails in the night sky. Both the stratosphere (next layer down) and the mesosphere are considered the middle atmosphere.
The transition boundary which separates the mesosphere from the stratosphere is called the stratopause.
height, composition, boundaries
Stratosphere
The Stratosphere extends around 50 km down to anywhere from 7 to 20 km above the Earth’s surface. This layer holds 19 percent of the atmosphere’s gases but very little water vapor.
In this region the temperature increases with height. Heat is produced in the process of the formation of Ozone and this heat is responsible for temperature increases from an average -51°C at tropopause to a maximum of about -15°C at the top of the stratosphere.
This increase in temperature with height means warmer air is located above cooler air. This prevents “convection” as there is no upward vertical movement of the gases. As such the location of the bottom of this layer is readily seen by the ‘anvil-shaped’ tops of cumulonimbus clouds
Troposphere
Lowest layer containing most of Earth’s atmosphere (75-80%). Tropopause (boundary btwn trosophere and stratosphere) is usually at ~10km - the jet stream is just below this). The height of the top of the troposphere varies with latitude (it is lowest over the poles and highest at the equator), with season (it is lower in winter and higher in summer), and time of day. It can be as high as 20 km near the equator, and as low as 7 km over the poles in winter.
Almost all weather occurs within this layer [nearly all of the water vapor and dust particles in the atmosphere are in the troposphere. That is why most clouds are found in this lowest layer, too]. It is warmed from below (sunlight warms the ground or ocean, which in turn radiates the heat into the air right above it); air is warmest at the bottom of the troposphere near ground level, and temperature decreases with altitude** (higher up it gets colder). **Air pressure and density also decrease with altitude.
The troposphere is heated from below. Sunlight warms the ground or ocean, which in turn radiates the heat into the air right above it. This warm air tends to rise. That keeps the air in the troposphere “stirred up”. The top of the troposphere is quite cold. The temperature at the top of the troposphere is around -55° C
