- This article is about the atmospheric mesosphere, for the Earth's mantle see Mesosphere (mantle)
The mesosphere refers to the mantle in the region between the asthenosphere and the outer core. The upper boundary is defined as the sharp increase in seismic wave velocities and density at a depth of 660 km...
.
The
mesosphere (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...
words mesos
= middle and sphaira = ball) is the layer of the
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...
that is directly above the
stratosphereThe stratosphere is the second major layer of Earth's atmosphere, just above the troposphere, and below the mesosphere. 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...
and directly below the
thermosphereThe thermosphere is biggest of all the layers of the earth's atmosphere directly above the mesosphere and directly below the exosphere. Within this layer, ultraviolet radiation causes ionization. The International Space Station has a stable orbit within the upper part of the thermosphere, between...
. The mesosphere is located about 50 to 85 kilometers (30 to 50 miles) above the
EarthEarth is the third planet from the Sun. It is the fifth largest of the eight planets in the solar system, and the largest of the terrestrial planets in the Solar System in terms of diameter, mass and density...
's surface.
The stratosphere and mesosphere are referred to as the middle atmosphere.
- This article is about the atmospheric mesosphere, for the Earth's mantle see Mesosphere (mantle)
The mesosphere refers to the mantle in the region between the asthenosphere and the outer core. The upper boundary is defined as the sharp increase in seismic wave velocities and density at a depth of 660 km...
.
The
mesosphere (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...
words mesos
= middle and sphaira = ball) is the layer of the
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...
that is directly above the
stratosphereThe stratosphere is the second major layer of Earth's atmosphere, just above the troposphere, and below the mesosphere. 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...
and directly below the
thermosphereThe thermosphere is biggest of all the layers of the earth's atmosphere directly above the mesosphere and directly below the exosphere. Within this layer, ultraviolet radiation causes ionization. The International Space Station has a stable orbit within the upper part of the thermosphere, between...
. The mesosphere is located about 50 to 85 kilometers (30 to 50 miles) above the
EarthEarth is the third planet from the Sun. It is the fifth largest of the eight planets in the solar system, and the largest of the terrestrial planets in the Solar System in terms of diameter, mass and density...
's surface.
The stratosphere and mesosphere are referred to as the middle atmosphere. The
mesopause, at an altitude of 80–90 km, separates the mesosphere from the
thermosphereThe thermosphere is biggest of all the layers of the earth's atmosphere directly above the mesosphere and directly below the exosphere. Within this layer, ultraviolet radiation causes ionization. The International Space Station has a stable orbit within the upper part of the thermosphere, between...
—the second-outermost layer of the Earth's atmosphere. This is also around the same altitude as the
turbopauseThe turbopause marks the altitude in the Earth's atmosphere below which turbulent mixing dominates. The region below the turbopause is known as the homosphere, where the chemical constituents are well mixed and display identical height distributions; in other words, the chemical composition of the...
, below which different chemical species are well mixed due to turbulent eddies. Above this level the atmosphere becomes non-uniform; the
scale heightA scale height is a term often used in scientific contexts for a distance over which a quantity decreases by a factor of e...
s of different chemical species differ by their
molecular massThe molecular mass of a substance, frequently referred to by the older term molecular weight and abbreviated as MW, is the mass of one molecule of that substance, relative to the unified atomic mass unit u...
es.
Temperature
Within the mesosphere, temperature decreases with increasing
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...
. This is due to decreasing solar heating and increasing cooling by CO
2 radiative emission. The top of the mesosphere, called the
mesopauseThe mesopause is the temperature minimum at the boundary between the mesosphere and the thermosphere atmospheric regions. Due to the lack of solar heating and very strong cooling by radiative emission from CO2, the mesopause is the coldest place on Earth with temperatures as low as -100°C...
, is the coldest place on Earth. Temperatures in the upper mesosphere fall as low as , varying according to
latitudeLatitude, usually denoted by the Greek letter phi gives the location of a place on Earth north or south of the equator. Lines of Latitude are the imaginary horizontal lines shown running east-to-west on maps that run either north or south of the equator...
and
seasonA season is a division of the year, marked by changes in weather.Seasons result from the yearly revolution of the Earth around the Sun and the tilt of the Earth's axis relative to the plane of revolution...
.
Dynamical features
The main dynamical features in this region are
atmospheric tideAtmospheric tides are global-scale periodic oscillations of the atmosphere. In many ways they are analogous to ocean tides. Atmospheric tides can be excited by:*The regular day/night cycle in the insolation of the atmosphere...
s, internal atmospheric gravity waves (commonly called "
gravity wavesIn 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....
") and planetary waves. Most of these tides and waves are excited 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....
and lower
stratosphereThe stratosphere is the second major layer of Earth's atmosphere, just above the troposphere, and below the mesosphere. 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...
, and propagate upward to the mesosphere. In the mesosphere, gravity-wave amplitudes can become so large that the waves become unstable and dissipate. This dissipation deposits momentum into the mesosphere and largely drives global circulation.
Noctilucent cloudNoctilucent clouds, are tenuous cloud-like phenomena that are the "ragged-edge" of a much brighter and pervasive polar cloud layer called polar mesospheric clouds in the upper atmosphere, visible in a deep twilight. They are made of crystals of water ice. The name means roughly night shining in Latin...
s are located in the mesosphere. The mesosphere is also the region of the
ionosphereThe ionosphere is the uppermost part of the atmosphere, distinguished because it is ionized by solar radiation. It plays an important part in atmospheric electricity and forms the inner edge of the magnetosphere...
known as the D layer. The D layer is only present during the day, when some
ionizationIonization is the physical process of converting an atom or molecule into an ion by adding or removing charged particles such as electrons or other ions. This is often confused with dissociation ....
occurs with
nitric oxideNitric oxide or nitrogen monoxide is a chemical compound with chemical formula NO. This gas is an important signaling molecule in the body of mammals, including humans, and is an extremely important intermediate in the chemical industry...
being ionized by
Lyman seriesIn physics and chemistry, the Lyman series is the series of transitions and resulting ultraviolet emission lines of the hydrogen atom as an electron goes from n ≥ 2 to n = 1...
-alpha hydrogen radiation. The ionization is so weak that when night falls, and the source of ionization is removed, the free electron and ion form back into a neutral molecule.
Uncertainties
The mesosphere lies above the maximum altitude for
aircraftAn aircraft is a vehicle which is able to fly by being supported by the air, or in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil An aircraft is a vehicle which is able to fly by being supported...
and below the minimum altitude for orbital
spacecraftA spacecraft is a craft or machine designed for spaceflight. On a sub-orbital spaceflight, a spacecraft enters space then returns to the Earth. For an orbital spaceflight, a spacecraft enters a closed orbit around the planetary body. Spacecraft used for human spaceflight carry people on board as...
. It has only been accessed through the use of
sounding rocketsA sounding rocket, sometimes called a research rocket, is an instrument-carrying rocket designed to take measurements and perform scientific experiments during its sub-orbital flight. The origin of the term comes from nautical vocabulary, it refers to to sound, which means to throw a weighted...
. As a result, it is the most poorly understood part of the atmosphere. The presence of red sprites and blue jets (electrical discharges or
lightningLightning is an atmospheric discharge of electricity accompanied by thunder, which typically occurs during thunderstorms, and sometimes during volcanic eruptions or dust storms...
within the lower mesosphere),
noctilucent cloudNoctilucent clouds, are tenuous cloud-like phenomena that are the "ragged-edge" of a much brighter and pervasive polar cloud layer called polar mesospheric clouds in the upper atmosphere, visible in a deep twilight. They are made of crystals of water ice. The name means roughly night shining in Latin...
s and density shears within the poorly understood layer may have contributed to the
Space Shuttle Columbia disasterThe Space Shuttle Columbia disaster occurred on February 1, 2003, when the Space Shuttle Columbia disintegrated over Texas during re-entry into the Earth's atmosphere, with the loss of all seven crew members, shortly before it was scheduled to conclude its 28th mission, STS-107.The loss of Columbia...
.
Meteors
Millions of
meteorMETEOR is a metric for the evaluation of machine translation output. The metric is based on the harmonic mean of unigram precision and recall, with recall weighted higher than precision...
s enter the atmosphere, an average of 40 tons per day. Within the mesosphere most melt or vaporize as a result of collisions with the gas particles contained there. This results in a higher concentration of
ironIron is a metallic chemical element with the symbol Fe and atomic number 26. Iron is a group 8 and period 4 element and is therefore classified as a transition metal. Iron and iron alloys are by far the most common metals and the most common ferromagnetic materials in everyday use...
and other refractory materials reaching the surface.
External links