There is no distinct boundary between the atmosphere and space, but an imaginary line about 62 miles kilometers from the surface, called the Karman line , is usually where scientists say atmosphere meets outer space. The troposphere is the layer closest to Earth's surface.
It is 4 to 12 miles 7 to 20 km thick and contains half of Earth's atmosphere. Air is warmer near the ground and gets colder higher up. Nearly all of the water vapor and dust in the atmosphere are in this layer and that is why clouds are found here. The stratosphere is the second layer. It starts above the troposphere and ends about 31 miles 50 km above ground.
Ozone is abundant here and it heats the atmosphere while also absorbing harmful radiation from the sun. The air here is very dry, and it is about a thousand times thinner here than it is at sea level. Because of that, this is where jet aircraft and weather balloons fly. The mesosphere starts at 31 miles 50 km and extends to 53 miles 85 km high. The top of the mesosphere, called the mesopause, is the coldest part of Earth's atmosphere, with temperatures averaging about minus degrees F minus 90 C.
This layer is hard to study. Jets and balloons don't go high enough, and satellites and space shuttles orbit too high. Scientists do know that meteors burn up in this layer. The thermosphere extends from about 56 miles 90 km to between and miles and 1, km. The mesosphere is dark, with air pressure so low that a human could not survive in this layer. Temperature begins to increase again in the thermosphere. The increase in temperature, or inversion, is due in part to the absorption of UV and x-ray radiation and the impact of the solar wind — a continuous stream of protons and electrons given off by the sun.
In this layer, atoms and molecules escape into space, and higher altitude satellites orbit our planet. Skip to Main Content Area. Home About Resources References. Energy: The Driver of Climate. 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.
The concentration of water vapor decreases drastically with altitude. The upper troposphere has considerably less water vapor than air near the surface, the stratosphere and mesosphere have almost no water vapor, and the thermosphere contains none at all.
Air also contains tiny solid particles called aerosols , such as dust, sea salt, and ash from erupting volcanoes or forest fires.
Many of these particles are so small that they are microscopic. Others are large enough to see. Aerosols affect climate by helping clouds form and shading the planet by scattering or absorbing sunlight. In the last century, manufacturing and widespread use of combustion engines have increased the number of aerosols in the atmosphere as particulate matter spews from smokestacks and exhaust pipes.
Burning wood and other materials also add particles to the air. Like everything on Earth, the air is made of chemicals. Many of these chemical reactions help maintain healthy natural environments and are vital for plants and animals. Nitrogen gas in the atmosphere does almost nothing, but nitrogen elsewhere on Earth is essential for life. Through the nitrogen cycle , nitrogen makes its way into soil and water, binds with other elements, and can be used by living things.
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