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Stratosphere
*** Shopping-Tip: Stratosphere
:''This article is about the atmospheric layer; for the hotel in
Las Vegas, Nevada Las Vegas, see
Stratosphere Las Vegas.''
The '''stratosphere''' is a layer of
Earth's atmosphere that is stratified in temperature, with warmer layers higher up and cooler layers farther down. This is in contrast to the
troposphere near the Earth's surface, which is cooler higher up and warmer farther down. The stratosphere is situated between about 10 km and 50 km
altitude above the surface at moderate latitudes, while at the
geographical pole poles it starts at about 8 km altitude. The stratosphere sits directly above the
troposphere and directly below the
mesosphere.
The stratosphere is layered in temperature because it is heated from above by absorption of
ultraviolet radiation from the
Sun. Within this layer, temperature increases as altitude increases; the top of the stratosphere has a temperature of about 270
Kelvin K, about the same as the ground level temperature. This top is called the
stratopause, above which temperature again decreases with height. The vertical stratification, with warmer layers above and cooler layers below, makes the stratosphere
dynamically stable: there is no regular
convection and associated
turbulence in this part of the atmosphere. The heating is caused by an
ozone layer that absorbs solar
ultraviolet radiation, heating the upper layers of the stratosphere. The base of the stratosphere occurs where heating by conduction from above and heating by convection from below (through the troposphere) balance out; hence, the stratosphere begins at lower altitudes near the poles due to the lower ground
temperature there.
Commercial
airliner airliners typically cruise at an altitude near 10 km in temperate latitudes, in the lower reaches of the stratosphere. This is to avoid atmospheric
turbulence from the
convection in the
troposphere. Turbulence experienced in the cruise phase of flight is often caused by
convective overshoot from the troposphere below. Similarly, most
gliders soar on thermal plumes that rise through the troposphere above warm patches of ground; these plumes end at the base of the stratosphere, setting a limit to how high gliders can fly in most parts of the world. (Some gliders do fly higher, using
wave lift from mountain ranges to lift them into the stratosphere).
The stratosphere is a region of intense interactions among radiative, dynamical, and chemical processes, in which horizontal mixing of gaseous components proceeds much more rapidly than vertical mixing.
An interesting feature of stratospheric circulation is the
QBO quasi-Biennial Oscillation (QBO) in the tropical latitudes, which is driven by
gravity waves that are convectively generated in the
troposphere. The QBO induces a
secondary circulation that is important for the global stratospheric transport of tracers such as
ozone or
water vapor.
In northern hemispheric winter,
sudden stratospheric warmings can often be observed which are caused by the absorption of
Rossby waves in the stratosphere.
Ozone Depletion
{{main|Ozone depletion}}
The main cause of ozone depletion is the presence of ''chlorofluorocarbons'' (aka CFCs - CF2Cl2, CFCl3) in the Earth's '''stratosphere'''. Because CFCs are stable, inexpensive, non-toxic, flammable, or corrosive, they are used as propellants, as refrigerants, as solvents, etc. However, it is because of this stability that causes these CFCs to persist within the environment. These molecules eventually find their way to the stratosphere, where they undergo a series of chain reactions which ultimately lead to the destruction of the ozone layer.
The U.S. government banned the use of CFCs for aerosol propellants in 1980. Worldwide efforts to reduce the use of CFCs began in September 1987 and by 1996 an international ban was put into effect preventing the industrial production and release of CFCs. These efforts have been drastically thwarted by black market operations in China and Russia where up to $300 million worth of illegal CFCs are manufactured. The amounts of CFCs in the stratosphere will continue to rise until early 2000, and are expected to reach acceptable levels by mid-century.
See also
*
Léon Teisserenc de Bort (the discoverer of the stratosphere)
*
Edge of space
{{earthsatmosphere}}
Category:Atmosphere
cs:Stratosféra
da:Stratosfæren
de:Stratosphäre
es:Estratosfera
fr:Stratosphère
gl:Estratosfera
ko:성층권
he:סטרטוספירה
nl:Stratosfeer
ja:�層�
no:Stratosfæren
pl:Stratosfera
pt:Estratosfera
sk:Stratosféra
sr:СтратоÑ?фера
fi:Stratosfääri
sv:Stratosfär
vi:Tầng bình lưu
uk:СтратоÑ?фера
zh:平�层
*** Shopping-Tip: Stratosphere
