Look up. Way up. After that, the atmosphere blends into space. Trace amounts of carbon dioxide, methane, water vapor, and neon are some of the other gases that make up the remaining 0.
The atmosphere is divided into five different layers, based on temperature. The troposphere is thickest at the equator, and much thinner at the North and South Poles. The majority of the mass of the entire atmosphere is contained in the troposphere—between approximately 75 and 80 percent. Temperatures in the troposphere decrease with altitude. It reaches from the top of the troposphere, which is called the tropopause, to an altitude of approximately 50 kilometers 30 miles.
Temperatures in the stratosphere increase with altitude. A high concentration of ozone, a molecule composed of three atoms of oxygen, makes up the ozone layer of the stratosphere. This ozone absorbs some of the incoming solar radiation, shielding life on Earth from potentially harmful ultraviolet UV light, and is responsible for the temperature increase in altitude.
The top of the stratosphere is called the stratopause. Temperatures decrease in the mesosphere with altitude. The thermosphere is located above the mesopause and reaches out to around kilometers miles. Not much is known about the thermosphere except that temperatures increase with altitude.
The uppermost layer, that blends with what is considered to be outer space, is the exosphere. Also called a shooting star or falling star. The high temperature indicates the amount of the energy absorbed by the molecules but with so few in this layer, the total number of molecules is not enough to heat our skin. This layer extends from around 31 miles 50 km above the Earth's surface to 53 miles 85 km. The gases, including the oxygen molecules, continue to become denser as one descends.
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. The Stratosphere extends around 31 miles 50 km down to anywhere from 4 to 12 miles 6 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.
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.
Known as the lower atmosphere almost all weather occurs in this region. The stratosphere is very dry; air there contains little water vapor. Because of this, few clouds are found in this layer; almost all clouds occur in the lower, more humid troposphere. Polar stratospheric clouds PSCs are the exception.
PSCs appear in the lower stratosphere near the poles in winter. They are found at altitudes of 15 to 25 km 9. They appear to help cause the formation of the infamous holes in the ozone layer by "encouraging" certain chemical reactions that destroy ozone. PSCs are also called nacreous clouds. Air is roughly a thousand times thinner at the top of the stratosphere than it is at sea level. Because of this, jet aircraft and weather balloons reach their maximum operational altitudes within the stratosphere.
Due to the lack of vertical convection in the stratosphere, materials that get into the stratosphere can stay there for long times. Such is the case for the ozone-destroying chemicals called CFCs chlorofluorocarbons.
Large volcanic eruptions and major meteorite impacts can fling aerosol particles up into the stratosphere where they may linger for months or years, sometimes altering Earth's global climate.
0コメント