The Mesosphere-Layer of the Earth´s Atmosphere
The mesosphere is one of the layers of the earth´s atmosphere. It lies in between the stratosphere and the thermosphere and spans from about 50-85 km (30-55 miles) above the surface of the earth. In this layer, the temperature decreases with altitude. Below and above the mesosphere, there are boundaries that separate it from the other atmospheric layers;these are the stratopause below and the mesopause above. These transition regions mark the thickness of the mesosphere, which is of about 35 km (22 miles).
The air density is lower than the layers below, but it´s sufficient enough to create friction for the meteorites that enter it, causing them to burn up and leaving remnants of these rocky bodies in the atmosphere in the form of iron and other metals, before reaching the surface of the earth. As any other layer of the atmosphere, this one protects us from objects from outer space, such as meteors and ultraviolet radiation.
This layer of the atmosphere is one of the least known due aircraft and weather balloons are not able to reach these heights and the orbit at which satellites travel is high above the mesosphere. Scientist use sounding rockets-which make short elliptical flights that never go into orbit, to study this layer.
The Transition Regions
The earth´s atmosphere consists of five different layers;each one with its own distinct characteristics. Each layer has a transition region that separates them form the next layer. These layers and transition regions are the troposphere-tropopause, stratosphere-stratopause, mesosphere-mesopause, thermosphere-thermopause, and exosphere-exopause. Each of these permits life to exist on earth.
The troposphere, where 99% of the atmosphere´s mass is allows living things to breath and the stratosphere contains the ozone layer, which blocks UV rays. In the atmosphere, meteors are able to go through the exosphere and thermosphere, but when reaching the mesosphere a greater abundance of air molecules produces friccion causing them to disintegrate.
Above the stratosphere is the stratopause, which marks the temperature minimum for the mesosphere. At the top of the mesosphere is the mesopause, which is the coldest region in the atmosphere and probably of the earth, as here temperatures--143° C, colder than those found in antarctica.
Layers of the Atmosphere and Transition Regions
Mesospheric and Near Space phenomena
Atmospheric lightning transient luminous event
Auroras-polar lights or northern lights- is a natural light display that occurs in northern regions, such as the Arctic and Antarctic. They become luminous when the energized particles from the sun interact with atoms and molecules in the thermosphere, then they travwel throuhgh the earth´s magnetic field lines down to the Poles.
Meteors that reach the mesosphere interact with air molecules, causing them to burn up and light up in the sky. This is due that this rocky bodies enter the mesosphere at very high speeds that produce friccion against the thin layer of air particles. This helps protect the earth from the otherwise rocky bombardments.
Noctilucent clouds are formed ion the mesosphere and in the polar regions. They form at higher altitudes than tropospheric clouds and they usually glow in blueish color; They are most often seen aat higher altitudes when the sun sets below in the horizon.
The ionosphere is a region in the earth´s atmosphere that extends throughout the mesosphere, thermosphere and exosphere. In this region, air molecules and atoms are ionized by the energetic particles coming from the sun and from outer space-cosmic rays. Through the process of ionization, the ionosphere protects the earth by absorbing Extreme Ultraviolet Radiation in the F2 layer and lower energetic radiation at lower altitudes.
The Ozone Layer
This layer is located at about 20-30 km above from the earth´s surface. It protects the earth from harmful ultraviolet radiation. The highest levels of ozone-O3- are in the stratosphere where this gas absorbs sunlight with wavelenghts of 200-315 nm UV rays. Concentration of ozone is lower in the mesosphere; nevertheless, it adds to the absorption and protection of the earth against these harmful rays.
This is a photochemical reaction that occurs in the upper atmosphere and is the result of the interaction of UV radiation and the atoms and molecules that exist in atmosphere. When these molecules and atoms return to their neutral state, they release energy. Most of the airglow is due to oxygen, nitrogen and sodium. Whle airglow is produced at all layers of the atmosphere, the band that glows visibly is situated in between 80-95 km (50-60 miles) in altitude.
Atmospheric Tides (AT)
These are periodic oscillations of the atmosphere that are generated in the troposphere and stratosphere when water vapor and the ozone layer absorb solar radiation during the day and heat the atmosphere. They propagate upwards to the mesosphere and thermosphere, increasing in amplitude due to lower air densities as altitude increases. AT are categorized as regular fluctuations of temperature, wind, pressure and density.
Airglow in the Mesosphere
These are clouds that appear in the winter polar stratosphere at altitudes of between 15-25 km (9-15 miles). They are commonly observed before sunrise or sunset when the sun is anywhere from 2-6° below the horizon. They are related to ozone depletion through the production of chlorine which catalyzes ozone destruction.
Atmospheric Lightning Transient Luminous Event
They are very brief electrical formations that occur in the upper regions of the atmosphere and above larger thunderstorms. Sprites are believed to form due to the ionization of the upper atmosphere after a lightning strike. Blue jets are brighter than sprites and is a type of lightning that discharges from the positive region in a thundercloud and a negative layer above it. They occur in the fraction of one tenth of a second and usually extend uppward in the atmosphere. Elves are electronic pulses that occur in the ionosphere due to the excitation of nirogen molecules by a discharge from an thunderstorm in the lower atmosphere.
Red Sprites and Blue Jets
Gravity waves are atmospheric waves that can transport momentum up in the atmosphere. They form in the troposphere and stratosphere by convective storms. These waves propagate into the middle atmosphere where they grow in amplitude forming a fan-like pattern of waves and reaching breaking amplitudes at the mesosphere.
This transfer of momentum produces great dynamical characteristics in the atmosphere, including periodical wind turbulence at the tropics between easterly and westerly winds.
Gravity Waves in the clouds resembles that of altostratus clouds in the sky
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The mesosphere protects the earth by burning up meteors and asteroids before reaching the surface of the earth
Ice clouds-noctilucent clouds or polar mesospheric clouds-are visible at sunset from the earth´s poles
The mesosphere is made of the same gases-oxygen, carbon dioxide and nitrogen-the same way that the lower atmosphere but it´s less dense
The mesosphere´s temperature decreases with height, reaching its lowest,-90° C (-130° F), temperature at the mesopause
Sprites or elves are a type of mesospheric lightning
The mesosphere, along with other layers of the atmosphere help maintain earth´s climate suitable for life
Even though, there are few gas molecules in the mesosphere, they´re enough to produce friccion and cause meteors to melt
Mesosphere is Difficult to Study
This layer of the atmosphere is not easy to study; weather balloons have only reached 53 km of altitude, that´s the record and airplanes cannot fly that high due that at this altitude the air is very thin and lower altitudes mean more air resistance, so 35,000-42,000 feet is the regular flying altitude for airplanes. Satellites orbit at altitudes above the mesosphere due that the air molecules there are scarse so there is less air drag.
To study the mesosphere, there would have to be more scientific instruments capable of staying sufficient amounts of time there to get measurements.Scientists use sounding rockets and weather balloons that only measure the first km of this layer.
© 2018 Jose Juan Gutierrez