The
stratosphere is the second major layer of
Earth's atmosphereThe Earth's atmosphere is a layer of gases surrounding the planet Earth that is retained by Earth's gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention , and reducing temperature extremes between day and night...
, just above the
troposphereThe troposphere is the lowest portion of Earth's atmosphere. It contains approximately 75 percent of the atmosphere's mass and 99 percent of its water vapor and aerosols....
, and below the
mesosphereThe mesosphere is the layer of the Earth's atmosphere that is directly above the stratosphere and directly below the thermosphere. The mesosphere is located about 50 to 85 kilometers above the Earth's surface.The stratosphere and mesosphere are referred to as the middle atmosphere...
. It 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 border of the troposphere and stratosphere, the
tropopauseThe tropopause is the atmospheric boundary between the troposphere and the stratosphere. Going upward from the surface, it is the point where air ceases to cool with height, and becomes almost completely dry. More formally, it is the region of the atmosphere where the lapse rate changes from...
, is marked by where this inversion begins, which in terms of
atmospheric thermodynamicsIn the physical sciences, atmospheric thermodynamics is the study of heat and energy transformations in the earth’s atmospheric system. Following the fundamental laws of classical thermodynamics, atmospheric thermodynamics studies such phenomena as properties of moist air, formation of clouds,...
is the
equilibrium levelIn meteorology, the equilibrium level , or level of neutral buoyancy , is the height at which a rising parcel of air is at a temperature of equal warmth to it. This means that unstable air is now stable when it reaches the equilibrium level and convection stops...
.
The
stratosphere is the second major layer of
Earth's atmosphereThe Earth's atmosphere is a layer of gases surrounding the planet Earth that is retained by Earth's gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention , and reducing temperature extremes between day and night...
, just above the
troposphereThe troposphere is the lowest portion of Earth's atmosphere. It contains approximately 75 percent of the atmosphere's mass and 99 percent of its water vapor and aerosols....
, and below the
mesosphereThe mesosphere is the layer of the Earth's atmosphere that is directly above the stratosphere and directly below the thermosphere. The mesosphere is located about 50 to 85 kilometers above the Earth's surface.The stratosphere and mesosphere are referred to as the middle atmosphere...
. It 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 border of the troposphere and stratosphere, the
tropopauseThe tropopause is the atmospheric boundary between the troposphere and the stratosphere. Going upward from the surface, it is the point where air ceases to cool with height, and becomes almost completely dry. More formally, it is the region of the atmosphere where the lapse rate changes from...
, is marked by where this inversion begins, which in terms of
atmospheric thermodynamicsIn the physical sciences, atmospheric thermodynamics is the study of heat and energy transformations in the earth’s atmospheric system. Following the fundamental laws of classical thermodynamics, atmospheric thermodynamics studies such phenomena as properties of moist air, formation of clouds,...
is the
equilibrium levelIn meteorology, the equilibrium level , or level of neutral buoyancy , is the height at which a rising parcel of air is at a temperature of equal warmth to it. This means that unstable air is now stable when it reaches the equilibrium level and convection stops...
. The stratosphere is situated between about 10 km (6 miles) and 50 km (31 miles)
altitudeAltitude is defined based on the context in which it is used . As a general definition, altitude is a distance measurement, usually in the vertical or "up" direction, between a reference datum and a point or object...
above the surface at moderate latitudes, while at the
polesA geographical pole is either of the two points—the north pole and the south pole—on the surface of a rotating planet where the axis of rotation meets the surface of the body...
it starts at about 8 km (5 miles) altitude.
The word
stratosphere is from the
GreekGreek , an independent branch of the Indo-European family of languages, is the language of the Greeks. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. In its ancient form, it is the language of classical...
meaning 'stratified layer'and sphaira meaning ball.
Temperature
The stratosphere is layered in temperature because it is heated from above by absorption of
ultravioletUltraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than x-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
radiation from the
SunThe Sun is the star at the center of the Solar System. The Earth and other matter orbit the Sun, which by itself accounts for about 99.86% of the Solar System's mass....
. Within this layer, temperature increases as altitude increases (see temperature inversion); the top of the stratosphere has a temperature of about 270
KThe kelvin is a unit increment of temperature and is one of the seven SI base units. The Kelvin scale is a thermodynamic temperature scale where absolute zero, the theoretical absence of all thermal energy, is zero kelvin...
(−3°C or 29.6°F), just slightly below the freezing point of water. This top is called the
stratopauseThe stratopause is the level of the atmosphere which is the boundary between two layers, stratosphere and the mesosphere...
, above which temperature again decreases with height. The vertical
stratificationAtmospheric stratification is the division of the atmosphere into distinct layers, each with specific characteristics such as temperature or composition....
, with warmer layers above and cooler layers below, makes the stratosphere dynamically stable: there is no regular
convectionConvection is the movement of molecules within fluids . Convection is one of the major modes of heat transfer and mass transfer...
and associated
turbulenceIn fluid dynamics, turbulence or turbulent flow is a fluid regime characterized by chaotic, stochastic property changes. This includes low momentum diffusion, high momentum convection, and rapid variation of pressure and velocity in space and time. Flow that is not turbulent is called laminar flow...
in this part of the atmosphere. The heating is caused by an
ozone layerThe ozone layer is a layer in Earth's atmosphere which contains relatively high concentrations of ozone . This layer absorbs 93-99% of the sun's high frequency ultraviolet light, which is potentially damaging to life on earth. Over 91% of the ozone in Earth's atmosphere is present here...
that absorbs solar ultraviolet radiation, heating the upper layers of the stratosphere. The base of the stratosphere occurs where heating by
conductionIn heat transfer, conduction is the transfer of thermal energy between neighboring molecules in a substance due to a temperature gradient. It always takes place from a region of higher temperature to a region of lower temperature, and acts to equalize temperature differences. Conduction takes...
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
temperatureIn physics, temperature is a physical property of a system that underlies the common notions of hot and cold; something that feels hotter generally has the higher temperature. Temperature is one of the principal parameters of thermodynamics...
.The major reason for the temperature increase with altitude is that most of the ozone (O
3) is contained in the stratosphere. High energy ultraviolet light interacts with ozone to cause the temperature increase.
Aircraft flight
Commercial
airlinerAn airliner is a large fixed-wing aircraft for transporting passengers and cargo. Such planes are owned by airlines....
s typically cruise at altitudes of 9–12 km in temperate latitudes, in the lower reaches of the stratosphere. They do this to optimize
jet engineA jet engine is a reaction engine that discharges a fast moving jet of fluid to generate thrust in accordance with Newton's laws of motion. This broad definition of jet engines includes turbojets, turbofans, rockets, ramjets, pulse jets and pump-jets...
fuel burn, mostly thanks to the low temperatures encountered near the tropopause. It also allows them to stay above any hard weather, and avoid atmospheric
turbulenceIn fluid dynamics, turbulence or turbulent flow is a fluid regime characterized by chaotic, stochastic property changes. This includes low momentum diffusion, high momentum convection, and rapid variation of pressure and velocity in space and time. Flow that is not turbulent is called laminar flow...
from the
convectionConvection is the movement of molecules within fluids . Convection is one of the major modes of heat transfer and mass transfer...
in the
troposphereThe troposphere is the lowest portion of Earth's atmosphere. It contains approximately 75 percent of the atmosphere's mass and 99 percent of its water vapor and aerosols....
. Turbulence experienced in the cruise phase of flight is often caused by
convective overshootConvective overshoot is a phenomenon of convection carrying material beyond an unstable region of the atmosphere into a stratified, stable region...
from the troposphere below. Although a few
gliderUnpowered aircraft are a group of aerial vehicles that can fly without propulsion. They can be classified as gliders, balloons and kites. In this instance, 'flight' means a trajectory that is not merely a vertical descent such as a parachute. In the case of kites, the flight is not free, but...
s have achieved great altitudes in the powerful
thermalA thermal column is a column of rising air in the lower altitudes of the Earth's atmosphere. Thermals are created by the uneven heating of the Earth's surface from solar radiation, and an example of convection. The Sun warms the ground, which in turn warms the air directly above it....
s in thunderstorms, this is dangerous. Most high altitude flights by gliders use
lee wavesIn meteorology, lee waves are atmospheric standing waves. The most common form is mountain waves, which are atmospheric internal gravity waves...
from mountain ranges and were used to set the current record of 15,447m (50,671 feet).
Circulation and mixing
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 quasi-Biennial Oscillation (QBO) in the tropical latitudes, which is driven by
gravity waveIn fluid dynamics, gravity waves are waves generated in a fluid medium or at the interface between two media which has the restoring force of gravity or buoyancy....
s that are convectively generated in the
troposphereThe troposphere is the lowest portion of Earth's atmosphere. It contains approximately 75 percent of the atmosphere's mass and 99 percent of its water vapor and aerosols....
. The QBO induces a
secondary circulationA secondary circulation is a circulation induced in a rotating system. For example, the primary circulation of Earth's atmosphere is zonal. If however a parcel of air, that moves in a purely zonal direction, is accelerated or decelerated zonally, the Coriolis force will add a meridional component...
that is important for the global stratospheric transport of tracers such as
ozoneOzone or trioxygen is a simple triatomic molecule, consisting of three oxygen atoms. It is an allotrope of oxygen that is much less stable than the diatomic O
2. Ground-level ozone is an air pollutant with harmful effects on the respiratory systems of animals...
or
water vaporWater vapor or water vapour , also aqueous vapor, is the gas phase of water. Water vapor is one state of the water cycle within the hydrosphere. Water vapor can be produced from the evaporation or boiling of liquid water or from the sublimation of ice...
.
In northern hemispheric winter, sudden stratospheric warmings can often be observed which are caused by the absorption of
Rossby waveRossby waves are giant meanders in high-altitude winds that are a major influence on weather. Their emergence is due to shear in rotating fluids, so that the Coriolis force changes along the sheared coordinate. In planetary atmospheres, they are due to the variation in the Coriolis effect with...
s in the stratosphere.
See also
- Léon Teisserenc de Bort
Léon Philippe Teisserenc de Bort was a French meteorologist who became famous for his discovery of the stratosphere.-Instrumented balloons pioneer:...
and Richard AssmannRichard Assmann ; was a German meteorologist and physician who was a native of Magdeburg....
(the discoverers of the stratosphere)
- Paris Gun
The Paris Gun was a German artillery piece used to bombard Paris during World War I. This oversized railway gun was in service from March-August 1918. When it was first employed, Parisians believed they'd been bombed by a new type of high-altitude zeppelin, as neither the sound of an airplane nor...
(first artificial object to reach stratosphere)
- SR-71 Blackbird
The Lockheed SR-71 is an advanced, long-range, Mach 3 strategic reconnaissance aircraft developed from the Lockheed A-12 and YF-12A aircraft by the Lockheed Skunk Works as a Black project. The SR-71 was unofficially named the Blackbird, and called the Habu by its crews, referring to an Okinawan...
- Concorde
The Aérospatiale-BAC Concorde aircraft was a turbojet-powered supersonic passenger airliner, a supersonic transport . It was a product of an Anglo-French government treaty, combining the manufacturing efforts of Aérospatiale and the British Aircraft Corporation...
- Lockheed U-2
The Lockheed U-2, nicknamed "Dragon Lady", is a single-engine, very high-altitude reconnaissance aircraft operated by the United States Air Force and previously flown by the Central Intelligence Agency. It provides day and night, very high-altitude , all-weather surveillance...
- RQ-4 Global Hawk
The Northrop Grumman RQ-4 Global Hawk is an unmanned aerial vehicle used by the United States Air Force as a surveillance aircraft....
- Twinjet
A twinjet is a jet aircraft powered by two engines. There are two common configurations of the engines; one sees either engine slung under a wing, and the other sees them mounted at the back of the fuselage. Twinjets tend to be quieter and more efficient than aircraft with either three or four...
s service ceilingIn aeronautics, a ceiling is the maximum density altitude an aircraft can reach under a set of conditions.-Service ceiling:The service ceiling attempts to capture the maximum usable altitude of an aircraft...
- Le Grand Saut