The Regions of Our Atmosphere
The mesosphere begins at an altitude of about 50 kilometers (30 miles), as temperature begins to decrease with altitude.
The stratosphere begins about 9-12 kilometers (16-17 kilometers in the tropics) above Earth's surface. The stratosphere is heated from above (primarily as oxygen and ozone absorb solar ultraviolet radiation). Temperature in the stratosphere increases with altitude. In this region (Latin: stratum, layer), mixing is much slower and the "ozone layer" is found here.
The troposphere begins at the Earth's surface, which acts as a source of heat resulting from absorption of visible sunlight. The temperature decreases with height in the troposphere, and so the air is well mixed in this region (Greek: tropos, a turning). Weather occurs in this layer, and most commercial airliners fly in it.
Research Overview
It has become increasingly clear that humans are changing the chemical composition of the atmosphere in ways that can affect conditions at the Earth's surface – with potential consequences for all Earth's inhabitants. At the core of CSD's research today is the desire to understand atmospheric processes underlying some of the most challenging environmental issues of our time: climate change, air quality, and the stratospheric ozone layer.
Greenhouse gases emitted from natural and human-related activities affect climate, and the climate system is warming. Human activities, such as combustion of fossil fuels, release gases and particles that can form harmful pollution in the troposphere, the atmospheric layer nearest to Earth's surface. Poor air quality prematurely kills more than 60,000 people in the United States every year, according to the U.S. Environmental Protection Agency. And in the stratosphere, a "blanket" of ozone – the "ozone layer" – shields us from the harmful effects of the Sun's ultraviolet radiation. Some chemicals released into the atmosphere by people can deplete this protective ozone layer, which in turn can lead to crop damage, harm to natural ecosystems, and skin cancer. These global environmental challenges motivate CSD research.
CSD also assesses the current state of scientific understanding on these three topics and interacts with those who use this information as the scientific basis for decisions – within NOAA, in the United States, and around the globe.
Climate Change |
Air Quality |
Ozone Layer |
Assessments |
Research Groups |