Insel Air

IATA 7I ICAO INC Callsign INSELAIR
Founded	1993, operational since 2006
Hubs	4 Flamingo International Airport Hato International Airport (Main) Princess Juliana International Airport Queen Beatrix International Airport
Focus cities	3 Kralendijk, Bonaire Miami, Florida Philipsburg, St. Maarten
Frequent-flyer program	Insel Star Miles
Airport lounge	Plesman Lounge
Alliance	Pan Caribbean Alliance
Subsidiaries	Insel Air Aruba
Fleet size	11(+2 used for parts)
Destinations	16
Company slogan	Reaching Higher
Headquarters	Curaçao
Key people	Edward Heerenveen (CGIA), Albert Kluyver (CEO), Jurgen Lippinkhof (CCO),Charley De Meza (CFO),Henry van der Kwast (President of Supervisory Board)
Website	http://www.fly-inselair.com/

Insel Air MD-80 taxiing to the gate at Hato International Airport

Insel Air International B.V., doing business as Insel Air, is an airline based in Willemstad, Curaçao.^[1] It has Hato International Airport in Curaçao as its home base. Insel is German for island. Insel Air was incorporated as a private limited liability company (Dutch: Besloten Vennootschap) on September 8, 1993 and is registered with the Chamber of Commerce and Industry of Curaçao under number 64577.

History[link]

Insel Air is a private initiative of various businesses and financial institutions who recognized the need and importance for a Curaçao-based and owned airline to provide reliable quality service to regional destinations for a reasonable price.

The airline started operations in August 2006 with one Embraer 110-P1 Bandeirante flying from Curaçao. The first flight was to the neighbouring island of Aruba. Soon after the daily scheduled flights to Aruba, Insel Air started with flights to the other neighbouring island of Bonaire and also Las Piedras in Venezuela.

Since January 2007, Insel Air serves the Eastern and Northern Caribbean islands through Sint Maarten with a McDonnell Douglas MD-83 and since June 2008 also with a McDonnell Douglas MD-82. They have also added services to Miami via Curacao and Bonaire.

In September 2009, Insel Air took delivery of a second MD-82 aircraft. The aircraft arrived at Curacao as N434AG also featuring the new logo and being the only MD-80 with the known "screwdriver tail" (at the time). The aircraft was later re-registered as PJ-MDC.

Insel took delivery of its fourth MD80 (third MD82) on December 4, 2009 and a fifth MD80 (fourth MD82) in May 2011. Insel Air started in 2011 with four destinations – Medellin in Colombia, Charlotte in the US and Barquisimeto and Caracas in Venezuela.

2011[link]

Following the introduction of new service to Medellin and Bogota in Colombia and Charlotte in the USA, the airline's plans were underway to add a fifth MD-80 during the first quarter of 2011, which arrived on the 12 May 2011. Insel Air supervisory board member Niko Kluyver, says the flights should begin in the April timeframe. The Medellin flight began on 15 April 2011. Insel Air currently has an interline agreement with Charlotte-hubbed US Airways, covering service to Curaçao and Bonaire. Apart from the new flights to Charlotte and Bogota and Medellin, Insel Air is also looking to introduce service to Brazil and Argentina. Acknowledging the carrier's MD-80 fleet doesn't necessarily have the range to reach Argentina, Kluyver says the carrier might consider another aircraft type, "depending on what type of work we do with others".

The Company also completed the IATA operational safety audit (IOSA) and has joined ALTA, the Latin American and Caribbean Air Transport Association, in November 2011.^[2]

Insel Air and Tiara Air sign agreement[link]

Aruba national airline Tiara Air and the Aruban government recently announced a collaboration with Curaçao national airline Insel Air. The collaboration should enforce optimal use of the touristic routes to Aruba.

In order to serve passengers best, the agreement is valid for all routes that both airlines operate. The Aruban government also stated that it was committed to release an AOC (Air Operating Certificate) to Insel Air within three months, making it possible for Insel Air to also proceed as an Aruban airline under the name "Insel Air Aruba."

Due to the AOC, Insel Air Aruba will be able to operate many touristic flights to Aruba, therefore creating more inbound flights for the island.

According to Mr. E.K. Heerenveen, Chief General and International Affairs, "In this new agreement Insel Air Aruba will operate three Fokker 50 and one MD-80 increasing the total availability of seats to 50000 a month. Due to the cooperation with Tiara Air an extra 40.000 seats per month will be added, totaling to 90.000 seats per month.

Insel Air and KLM sign agreement[link]

Insel Air and KLM have reached an agreement for mutual interline cooperation.

InselAir International InselAir and KLM - Royal Dutch Airlines have entered into an interline agreement on Insel Air destinations, thus expanding their services to their passengers.

As of March 27, 2011, passengers carrying a KLM ticket can now also fly to all Insel Air destinations. Passengers will be transported 'comfortably and quickly' on one ticket and with automatic baggage transfer via InselAir's hubs in Curacao and Sint Maarten. Due to this agreement, KLM passengers can now connect seamlessly and continue their flights to more and to different destinations via InselAir’s flights.

For Kingston (Jamaica), San Juan (Puerto Rico), Santo Domingo in the Dominican Republic, Port au Prince (Haiti) and Las Piedras (Venezuela), KLM and Insel Air have reached a special agreement making it even more attractive for the passengers to reach these destinations.

InselAir is in the process of acquiring 3 Fokker 50 aircraft, (50-seater Turboprop) which will be incorporated into InselAir’s fleet to enhance connections and increase the flights on existing and new destinations.

Insel Air and US Airways sign agreement[link]

Due to the interline agreement with US Airways, passengers can get ticketed through on US Airways flights and vice versa, making it possible to connect to 58 US Airway destinations within 2,5 hours of the InselAir arrival and departure time in Charlotte.

Insel Air uses Sita airline management system.

Loyalty programme[link]

Insel Air's frequent flyer/loyalty programme is called "Insel StarMiles" in which members earn points for miles flown, with benefits such as priority check-in and free bagagge allowances. Membership levels include Basic, Silver, Gold and Diamond.

Livery[link]

Insel Air has a very simple livery on all of its aircraft. The fuselage is all white with the logo next to the main exit. The tail has a blue colour with a yellow curved line flowing horizontally on the tail, it also includes two white stars representing Curaçao and Klein Curaçao "small curacao". The tail entirely represents the national flag of the island of Curacao. The Embraers have a darker colored tail and a thicker and more curved line than the MD80s and the MD80's also feature the new logo update, while the Embraers are still unknown if they will receive this update.

The new fleet consisting of 3 Fokker 50 will also receive a new logo containing the Arubian official logo (The resembling that of Tiara Air, as part of the agremeent of the two airlines and the Arubian government), as these aircraft will operate under the new company Insel Air Aruba.

Destinations[link]

Insel Air serve the following destinations, as at March 2012:

City	Country	Airport	Notes
Oranjestad	Aruba	Queen Beatrix International Airport
Kralendijk	Bonaire	Flamingo International Airport
Manaus	Brazil	Eduardo Gomes International Airport*
Medellin	Colombia	José María Córdova International Airport
Barranquilla	Colombia	Ernesto Cortissoz International Airport*
Bogota	Colombia	El Dorado International Airport*
Havana	Cuba	José Martí International Airport*
Willemstad	Curacao	Hato International Airport
San José	Costa Rica	Juan Santamaría International Airport*
Santo Domingo	Dominican Republic	Las Américas International Airport
Punta Cana	Dominican Republic	Punta Cana International Airport	Seasonal
Port-au-Prince	Haiti	Toussaint Louverture International Airport
Kingston	Jamaica	Norman Manley International Airport
San Juan	Puerto Rico	Luis Muñoz Marín International Airport
Philipsburg	Sint Maarten	Princess Juliana International Airport
Paramaribo	Suriname	Johan Adolf Pengel International Airport
Miami	United States	Miami International Airport
Charlotte	United States	Charlotte/Douglas International Airport
Orlando	United States	Orlando International Airport	Seasonal
Punto Fijo	Venezuela	Josefa Camejo International Airport
Valencia	Venezuela	Arturo Michelena International Airport
Caracas	Venezuela	Simón Bolívar International Airport (Venezuela)
Maracaibo	Venezuela	La Chinita International Airport*
Barquisimeto	Venezuela	Jacinto Lara International Airport

Future planned destinations *

Terminated destinations[link]

Insel Air previously served the following destination.

City	Country	Airport
Port of Spain	Trinidad and Tobago	Piarco International Airport

Fleet[link]

As of March 2012, the Insel Air fleet consists of the following aircraft.^[3]

The fleet age for Insel Air's MD-80's is 24.7 years. The airline is also the only operator of the Fokker 50 in the Caribbean region.

Previously operated[link]

• 2 Bombardier Dash 8-300 (leased from Voyageur Airways)
• 2 Dash 6-300 Twin Otter (leased)
• 1 McDonnell Douglas MD-82 (leased from World Atlantic Airlines)

Incidents and Accidents[link]

On October 21, 2011, one of Insel Air's McDonnell Douglas MD-82's performing flight 7I 904 from Miami International Airport to Curacao's Hato International Airport with 144 passengers, was en route at FL330 near Santo Domingo (Dominican Republic) when the crew diverted to Santo Domingo's Las Américas International Airport due to a smoke indication in the cargo compartment. The aircraft landed safely, with no injuries. A replacement aircraft reached Curacao with a delay of 9 hours. The airport had reported the aircraft diverted because of mechanical problems with an engine.

The airline later explained that the crew received a cargo smoke detector indication, discharged the fire suppression system of that cargo compartment and diverted to Santo Domingo. The aircraft is undergoing thorough examination before returning to service.^[4]

External links[link]

Wikimedia Commons has media related to: Insel Air

• Insel Air
• Insel Air Fleet
• Insel Air Pictures

References[link]

Blue light is scattered more than other wavelengths by the gases in the atmosphere, giving the Earth a blue halo when seen from space.

Limb view, of the Earth's atmosphere. Colours roughly denote the layers of the atmosphere.

This image shows the moon at centre, with the limb of Earth near the bottom transitioning into the orange-coloured troposphere, the lowest and most dense portion of the Earth's atmosphere. The troposphere ends abruptly at the tropopause, which appears in the image as the sharp boundary between the orange- and blue- coloured atmosphere. The silvery-blue noctilucent clouds extend far above the Earth's troposphere.

The atmosphere of Earth 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 (greenhouse effect), and reducing temperature extremes between day and night (the diurnal temperature variation).

Atmospheric stratification describes the structure of the atmosphere, dividing it into distinct layers, each with specific characteristics such as temperature or composition. The atmosphere has a mass of about 5×10¹⁸ kg, three quarters of which is within about 11 km (6.8 mi; 36,000 ft) of the surface. The atmosphere becomes thinner and thinner with increasing altitude, with no definite boundary between the atmosphere and outer space. An altitude of 120 km (75 mi) is where atmospheric effects become noticeable during atmospheric reentry of spacecraft. The Kármán line, at 100 km (62 mi), also is often regarded as the boundary between atmosphere and outer space.

Air is the name given to atmosphere used in breathing and photosynthesis. Dry air contains roughly (by volume) 78.09% nitrogen, 20.95% oxygen, 0.93% argon, 0.039% carbon dioxide, and small amounts of other gases. Air also contains a variable amount of water vapor, on average around 1%. While air content and atmospheric pressure vary at different layers, air suitable for the survival of terrestrial plants and terrestrial animals is currently only known to be found in Earth's troposphere and artificial atmospheres.

Composition[link]

Composition of Earth's atmosphere. The lower pie represents the trace gases which together compose 0.039% of the atmosphere. Values normalized for illustration. The numbers are from a variety of years (mainly 1987, with CO₂ and methane from 2009) and do not represent any single source.

Mean atmospheric water vapor

Air is mainly composed of nitrogen, oxygen, and argon, which together constitute the major gases of the atmosphere. The remaining gases are often referred to as trace gases,^[1] among which are the greenhouse gases such as water vapor, carbon dioxide, methane, nitrous oxide, and ozone. Filtered air includes trace amounts of many other chemical compounds. Many natural substances may be present in tiny amounts in an unfiltered air sample, including dust, pollen and spores, sea spray, and volcanic ash. Various industrial pollutants also may be present, such as chlorine (elementary or in compounds), fluorine compounds, elemental mercury, and sulfur compounds such as sulfur dioxide [SO₂].

Structure of the atmosphere[link]

Principal layers[link]

In general, air pressure and density decrease in the atmosphere as height increases. However, temperature has a more complicated profile with altitude. Because the general pattern of this profile is constant and recognizable through means such as balloon soundings, temperature provides a useful metric to distinguish between atmospheric layers. In this way, Earth's atmosphere can be divided into five main layers. From highest to lowest, these layers are:

Exosphere[link]

The outermost layer of Earth's atmosphere extends from the exobase upward. It is mainly composed of hydrogen and helium. The particles are so far apart that they can travel hundreds of kilometers without colliding with one another. Since the particles rarely collide, the atmosphere no longer behaves like a fluid. These free-moving particles follow ballistic trajectories and may migrate into and out of the magnetosphere or the solar wind.

Thermosphere[link]

Temperature increases with height in the thermosphere from the mesopause up to the thermopause, then is constant with height. Unlike in the stratosphere, where the inversion is caused by absorption of radiation by ozone, in the thermosphere the inversion is a result of the extremely low density of molecules. The temperature of this layer can rise to 1,500 °C (2,700 °F), though the gas molecules are so far apart that temperature in the usual sense is not well defined. The air is so rarefied that an individual molecule (of oxygen, for example) travels an average of 1 kilometer between collisions with other molecules.^[3] The International Space Station orbits in this layer, between 320 and 380 km (200 and 240 mi). Because of the relative infrequency of molecular collisions, air above the mesopause is poorly mixed compared to air below. While the composition from the troposphere to the mesosphere is fairly constant, above a certain point, air is poorly mixed and becomes compositionally stratified. The point dividing these two regions is known as the turbopause. The region below is the homosphere, and the region above is the heterosphere. The top of the thermosphere is the bottom of the exosphere, called the exobase. Its height varies with solar activity and ranges from about 350–800 km (220–500 mi; 1,100,000–2,600,000 ft).^{[citation needed]}

Mesosphere[link]

The mesosphere extends from the stratopause to 80–85 km (50–53 mi; 260,000–280,000 ft). It is the layer where most meteors burn up upon entering the atmosphere. Temperature decreases with height in the mesosphere. The mesopause, the temperature minimum that marks the top of the mesosphere, is the coldest place on Earth and has an average temperature around −85 °C (−120 °F; 190 K).^[4] At the mesopause, temperatures may drop to −100 °C (−150 °F; 170 K).^[5] Due to the cold temperature of the mesosphere, water vapor is frozen, forming ice clouds (or Noctilucent clouds). A type of lightning referred to as either sprites or ELVES, form many miles above thunderclouds in the troposphere.

Stratosphere[link]

The stratosphere extends from the tropopause to about 51 km (32 mi; 170,000 ft). Temperature increases with height due to increased absorption of ultraviolet radiation by the ozone layer, which restricts turbulence and mixing. While the temperature may be −60 °C (−76 °F; 210 K) at the tropopause, the top of the stratosphere is much warmer, and may be near freezing^{[citation needed]}. The stratopause, which is the boundary between the stratosphere and mesosphere, typically is at 50 to 55 km (31 to 34 mi; 160,000 to 180,000 ft). The pressure here is 1/1000 sea level.

Troposphere[link]

The troposphere begins at the surface and extends to between 9 km (30,000 ft) at the poles and 17 km (56,000 ft) at the equator,^[6] with some variation due to weather. The troposphere is mostly heated by transfer of energy from the surface, so on average the lowest part of the troposphere is warmest and temperature decreases with altitude. This promotes vertical mixing (hence the origin of its name in the Greek word "τροπή", trope, meaning turn or overturn). The troposphere contains roughly 80% of the mass of the atmosphere.^[7] The tropopause is the boundary between the troposphere and stratosphere.

Other layers[link]

Within the five principal layers determined by temperature are several layers determined by other properties:

• The ozone layer is contained within the stratosphere. In this layer ozone concentrations are about 2 to 8 parts per million, which is much higher than in the lower atmosphere but still very small compared to the main components of the atmosphere. It is mainly located in the lower portion of the stratosphere from about 15–35 km (9.3–22 mi; 49,000–110,000 ft), though the thickness varies seasonally and geographically. About 90% of the ozone in our atmosphere is contained in the stratosphere.
• The ionosphere, the part of the atmosphere that is ionized by solar radiation, stretches from 50 to 1,000 km (31 to 620 mi; 160,000 to 3,300,000 ft) and typically overlaps both the exosphere and the thermosphere. It forms the inner edge of the magnetosphere. It has practical importance because it influences, for example, radio propagation on the Earth. It is responsible for auroras.
• The homosphere and heterosphere are defined by whether the atmospheric gases are well mixed. In the homosphere the chemical composition of the atmosphere does not depend on molecular weight because the gases are mixed by turbulence.^[8] The homosphere includes the troposphere, stratosphere, and mesosphere. Above the turbopause at about 100 km (62 mi; 330,000 ft) (essentially corresponding to the mesopause), the composition varies with altitude. This is because the distance that particles can move without colliding with one another is large compared with the size of motions that cause mixing. This allows the gases to stratify by molecular weight, with the heavier ones such as oxygen and nitrogen present only near the bottom of the heterosphere. The upper part of the heterosphere is composed almost completely of hydrogen, the lightest element.
• The planetary boundary layer is the part of the troposphere that is nearest the Earth's surface and is directly affected by it, mainly through turbulent diffusion. During the day the planetary boundary layer usually is well-mixed, while at night it becomes stably stratified with weak or intermittent mixing. The depth of the planetary boundary layer ranges from as little as about 100 m on clear, calm nights to 3000 m or more during the afternoon in dry regions.

The average temperature of the atmosphere at the surface of Earth is 14 °C (57 °F; 287 K)^[9] or 15 °C (59 °F; 288 K),^[10] depending on the reference.^{[11] [12][13]}

Physical properties[link]

Comparison of the 1962 US Standard Atmosphere graph of geometric altitude against air density, pressure, the speed of sound and temperature with approximate altitudes of various objects.^[14]

Pressure and thickness[link]

The average atmospheric pressure at sea level is about 1 atmosphere (atm) = 101.3 kPa (kilopascals) = 14.7 psi (pounds per square inch) = 760 torr = 29.92 inches of mercury (symbol Hg). Total atmospheric mass is 5.1480×10¹⁸ kg (1.135×10¹⁹ lb),^[15] about 2.5% less than would be inferred from the average sea level pressure and the Earth's area of 51007.2 megahectares, this portion being displaced by the Earth's mountainous terrain. Atmospheric pressure is the total weight of the air above unit area at the point where the pressure is measured. Thus air pressure varies with location and weather.

If the atmosphere had a uniform density, it would terminate abruptly at an altitude of 8.50 km (27,900 ft). It actually decreases exponentially with altitude, dropping by half every 5.6 km (18,000 ft) or by a factor of 1/e every 7.64 km (25,100 ft), the average scale height of the atmosphere below 70 km (43 mi; 230,000 ft). However, the atmosphere is more accurately modeled with a customized equation for each layer that takes gradients of temperature, molecular composition, solar radiation and gravity into account.

In summary, the mass of the earth's atmosphere is distributed approximately as follows:^[16]

• 50% is below 5.6 km (18,000 ft).
• 90% is below 16 km (52,000 ft).
• 99.99997% is below 100 km (62 mi; 330,000 ft), the Kármán line. By international convention, this marks the beginning of space where human travelers are considered astronauts.

By comparison, the summit of Mt. Everest is at 8,848 m (29,029 ft); commercial airliners typically cruise between 10 km (33,000 ft) and 13 km (43,000 ft) where the thinner air improves fuel economy; weather balloons reach 30.4 km (100,000 ft) and above; and the highest X-15 flight in 1963 reached 108.0 km (354,300 ft).

Even above the Kármán line, significant atmospheric effects such as auroras still occur. Meteors begin to glow in this region though the larger ones may not burn up until they penetrate more deeply. The various layers of the earth's ionosphere, important to HF radio propagation, begin below 100 km and extend beyond 500 km. By comparison, the International Space Station and Space Shuttle typically orbit at 350–400 km, within the F-layer of the ionosphere where they encounter enough atmospheric drag to require reboosts every few months. Depending on solar activity, satellites can still experience noticeable atmospheric drag at altitudes as high as 700–800 km.

Density and mass[link]

Temperature and mass density against altitude from the NRLMSISE-00 standard atmosphere model (the eight dotted lines in each "decade" are at the eight cubes 8, 27, 64, ..., 729)

The density of air at sea level is about 1.2  kg/m³ (1.2 g/L). Density is not measured directly but is calculated from measurements of temperature, pressure and humidity using the equation of state for air (a form of the ideal gas law). Atmospheric density decreases as the altitude increases. This variation can be approximately modeled using the barometric formula. More sophisticated models are used to predict orbital decay of satellites.

The average mass of the atmosphere is about 5 quadrillion (5×10¹⁵) tonnes or 1/1,200,000 the mass of Earth. According to the American National Center for Atmospheric Research, "The total mean mass of the atmosphere is 5.1480×10¹⁸ kg with an annual range due to water vapor of 1.2 or 1.5×10¹⁵ kg depending on whether surface pressure or water vapor data are used; somewhat smaller than the previous estimate. The mean mass of water vapor is estimated as 1.27×10¹⁶ kg and the dry air mass as 5.1352 ±0.0003×10¹⁸ kg."

Optical properties[link]

Solar radiation (or sunlight) is the energy the Earth receives from the Sun. The Earth also emits radiation back into space, but at longer wavelengths that we cannot see. Part of the incoming and emitted radiation is absorbed or reflected by the atmosphere.

Scattering[link]

When light passes through our atmosphere, photons interact with it through scattering. If the light does not interact with the atmosphere, it is called direct radiation and is what you see if you were to look directly at the Sun. Indirect radiation is light that has been scattered in the atmosphere. For example, on an overcast day when you cannot see your shadow there is no direct radiation reaching you, it has all been scattered. As another example, due to a phenomenon called Rayleigh scattering, shorter (blue) wavelengths scatter more easily than longer (red) wavelengths. This is why the sky looks blue; you are seeing scattered blue light. This is also why sunsets are red. Because the Sun is close to the horizon, the Sun's rays pass through more atmosphere than normal to reach your eye. Much of the blue light has been scattered out, leaving the red light in a sunset.

Absorption[link]

Different molecules absorb different wavelengths of radiation. For example, O₂ and O₃ absorb almost all wavelengths shorter than 300 nanometers. Water (H₂O) absorbs many wavelengths above 700 nm. When a molecule absorbs a photon, it increases the energy of the molecule. We can think of this as heating the atmosphere, but the atmosphere also cools by emitting radiation, as discussed below.

Rough plot of Earth's atmospheric transmittance (or opacity) to various wavelengths of electromagnetic radiation, including visible light.

The combined absorption spectra of the gases in the atmosphere leave "windows" of low opacity, allowing the transmission of only certain bands of light. The optical window runs from around 300 nm (ultraviolet-C) up into the range humans can see, the visible spectrum (commonly called light), at roughly 400–700 nm and continues to the infrared to around 1100 nm. There are also infrared and radio windows that transmit some infrared and radio waves at longer wavelengths. For example, the radio window runs from about one centimeter to about eleven-meter waves.

Emission[link]

Emission is the opposite of absorption, it is when an object emits radiation. Objects tend to emit amounts and wavelengths of radiation depending on their "black body" emission curves, therefore hotter objects tend to emit more radiation, with shorter wavelengths. Colder objects emit less radiation, with longer wavelengths. For example, the Sun is approximately 6,000 K (5,730 °C; 10,340 °F), its radiation peaks near 500 nm, and is visible to the human eye. The Earth is approximately 290 K (17 °C; 62 °F), so its radiation peaks near 10,000 nm, and is much too long to be visible to humans.

Because of its temperature, the atmosphere emits infrared radiation. For example, on clear nights the Earth's surface cools down faster than on cloudy nights. This is because clouds (H₂O) are strong absorbers and emitters of infrared radiation. This is also why it becomes colder at night at higher elevations. The atmosphere acts as a "blanket" to limit the amount of radiation the Earth loses into space.

The greenhouse effect is directly related to this absorption and emission (or "blanket") effect. Some chemicals in the atmosphere absorb and emit infrared radiation, but do not interact with sunlight in the visible spectrum. Common examples of these chemicals are CO₂ and H₂O. If there are too much of these greenhouse gases, sunlight heats the Earth's surface, but the gases block the infrared radiation from exiting back to space. This imbalance causes the Earth to warm, and thus climate change.

Refractive index[link]

The refractive index of air is close to, but just greater than 1. Systematic variations in refractive index can lead to the bending of light rays over long optical paths. One example is that, under some circumstances, observers onboard ships can see other vessels just over the horizon because light is refracted in the same direction as the curvature of the Earth's surface.

The refractive index of air depends on temperature, giving rise to refraction effects when the temperature gradient is large. An example of such effects is the mirage.

Circulation[link]

An idealised view of three large circulation cells.

Atmospheric circulation is the large-scale movement of air through the troposphere, and the means (with ocean circulation) by which heat is distributed around the Earth. The large-scale structure of the atmospheric circulation varies from year to year, but the basic structure remains fairly constant as it is determined by the Earth's rotation rate and the difference in solar radiation between the equator and poles.

Evolution of Earth's atmosphere[link]

Earliest atmosphere[link]

The outgassings of the Earth were stripped away by solar winds early in the history of the planet until a steady state was established, the first atmosphere. Based on today's volcanic evidence, this atmosphere would have contained 60% hydrogen, 20% oxygen (mostly in the form of water vapor), 10% carbon dioxide, 5 to 7% hydrogen sulfide, and smaller amounts of nitrogen, carbon monoxide, free hydrogen, methane and inert gases.^{[citation needed]}

A major rainfall led to the buildup of a vast ocean, enriching the other agents, first carbon dioxide and later nitrogen and inert gases. A major part of carbon dioxide exhalations were soon dissolved in water and built up carbonate sediments.

Second atmosphere[link]

Water-related sediments have been found dating from as early as 3.8 billion years ago.^[17] About 3.4 billion years ago, nitrogen was the major part of the then stable "second atmosphere". An influence of life has to be taken into account rather soon in the history of the atmosphere, since hints of early life forms are to be found as early as 3.5 billion years ago.^[18] The fact that this is not perfectly in line with the 30% lower solar radiance (compared to today) of the early Sun has been described as the "faint young Sun paradox".

The geological record however shows a continually relatively warm surface during the complete early temperature record of the Earth with the exception of one cold glacial phase about 2.4 billion years ago. In the late Archaean eon an oxygen-containing atmosphere began to develop, apparently from photosynthesizing algae which have been found as stromatolite fossils from 2.7 billion years ago. The early basic carbon isotopy (isotope ratio proportions) is very much in line with what is found today,^[19] suggesting that the fundamental features of the carbon cycle were established as early as 4 billion years ago.

Third atmosphere[link]

Oxygen content of the atmosphere over the last billion years. This diagram in more detail

The accretion of continents about 3.5 billion years ago^[20] added plate tectonics, constantly rearranging the continents and also shaping long-term climate evolution by allowing the transfer of carbon dioxide to large land-based carbonate storages. Free oxygen did not exist until about 1.7 billion years ago and this can be seen with the development of the red beds and the end of the banded iron formations. The Earth had a lot of iron in the beginning, and higher amounts of oxygen was not available in the atmosphere until all the iron had ben oxidized. This signifies a shift from a reducing atmosphere to an oxidising atmosphere. O₂ showed major ups and downs until reaching a steady state of more than 15%.^[21] The following time span was the Phanerozoic eon, during which oxygen-breathing metazoan life forms began to appear.

The amount of oxygen in the atmosphere has gone up and down during the last 600 million years. There was a peak 280 million years ago, when the amount of oxygen was about 30 %, much higher than today. The cause of changes in the atmosphere is two main processes: Plants converts carbon dioxide into the bodies of the plants, which emits oxygen into the atmosphere, and break down of pyrite rocks cause sulphur to be added to the oceans. Volcanos cause this sulphur to be oxidized, reducing the amount of oxygen in the atmosphere. But volcanos also emit carbon dioxide, so that plants can convert this to oxygen. The exact cause of the variation of oxygen in the atmosphere is not known. Periods with much oxygen in the atmosphere are believed to cause rapid development of animals. Even if the atmosphere today has only 21 percent oxygen, today is still regarded as a period with rapid development of animals because of a high amount of oxygen in the atmosphere.^[22]

Currently, anthropogenic greenhouse gases are increasing in the atmosphere. According to the Intergovernmental Panel on Climate Change, this increase is the main cause of global warming.^[23]

Air pollution[link]

Air pollution is the introduction of chemicals, particulate matter, or biological materials that cause harm or discomfort to organisms into the atmosphere.^[24] Stratospheric ozone depletion is believed to be caused by air pollution (chiefly from chlorofluorocarbons).^{[citation needed]}

See also[link]

	Atmosphere portal
	Environment portal

References[link]

External links[link]

Wikimedia Commons has media related to: Earth's atmosphere

• NASA atmosphere models
• NASA's Earth Fact Sheet
• American Geophysical Union: Atmospheric Sciences
• Outreach of the GEOmon project See how Earth atmosphere is observed and monitored by a European project that combines many approaches.
• Stuff in the Air Find out what the atmosphere contains.
• Layers of the Atmosphere
• Answers to several questions of curious kids related to Air and Atmosphere
• The AMS Glossary of Meteorology
• Paul Crutzen Interview Free video of Paul Crutzen Nobel Laureate for his work on decomposition of ozone talking to Harry Kroto Nobel Laureate by the Vega Science Trust.
• Slides describing the Earth's modern atmosphere

v t e Atmospheres Major Sun Venus Earth Mars Jupiter Saturn Titan Uranus Neptune Triton Pluto HD 209458 b Tenuous Mercury Moon Io Europa Ganymede Callisto Enceladus Dione Rhea See also Stellar atmosphere Coma (cometary) Extraterrestrial atmospheres