Temperature inversion

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Temperature inversion

• By Nikolai Kozak, Tomás Franco, Claudio González

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What is a temperature inversion?

• A temperature inversion is a thin layer of the
  atmosphere where the decrease in temperature with
  height is much less than normal (or in extreme
  cases, the temperature increases with height). An
  inversion, also called a "stable" air layer, acts
  like a lid, keeping normal convective overturning
  of the atmosphere from penetrating through the
  inversion. This can cause several weather-related
  effects.

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What is a temperature inversion?

• One is the trapping of pollutants below the
  inversion, allowing them to build up. If the sky
  is very hazy, or is sunsets are very red, there
  is likely an inversion somewhere in the lower
  atmosphere. This happens more frequently in high
  pressure zones, where the gradual sinking of air
  in the high pressure dome typically causes an
  inversion to form at the base of a sinking layer
  of air. Another effect is making clouds spread
  out and take on a flattened appearance.

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What is a temperature inversion?

• Still another effect is to prevent thunderstorms
  from forming. Even in an air mass that is hot and
  humid in the lowest layers, thunderstorms will be
  prevented if an inversion is keeping this air
  from rising. The opposite of a temperature
  inversion is an unstable air layer.

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When and Why Does This Happen?

• This happens when you have warm air that sits on
  top of a pool of cold air. Normally the
  temperature gets colder as you go higher in
  altitude. But on cold, calm nights, cold air will
  settle near the surface since cold air is heavier
  than warm air. In the meantime, a lack of winds
  will prevent the air from mixing. The pattern
  also usually creates ground fog. When the sun
  comes up, it will start to warm the air above the
  fog layer, creating an inversion -- it's actually
  warmer in higher altitudes than at the ground.

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When and Why Does This Happen?

• When the sun comes up, it will start to warm the
  air above the fog layer, creating an inversion --
  it's actually warmer in higher altitudes than at
  the ground. That helps further trap the cold air,
  and everything else in it, near the surface --
  including pollutants. That's why air quality
  suffers during inversions and usually leads to
  burn bans.

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• An example of this is Albuquerque

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But not everyone thinks that way

• Some people believe that the atmosphere often is
  highly layered, and such layering is most
  pronounced when a temperature inversion blocks
  intruding air from above and below The result can
  be a lower layer of polluted air, followed by 500
  to 1,000 feet of pristine air topped by another
  layer of pollution.

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And what are the Causes of Temperature Inversion?

• Under certain conditions, the normal vertical
  temperature gradient is inverted such that the
  air is colder near the surface of the Earth. This
  can occur when, for example, a warmer, less dense
  air mass moves over a cooler, denser air mass.
  This type of inversion occurs in the vicinity of
  warm fronts, and also in areas of oceanic
  upwelling such as along the California coast.

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And what are the Causes of Temperature Inversion?

• With sufficient humidity in the cooler layer,
  fog is typically present below the inversion cap.
  An inversion is also produced whenever radiation
  from the surface of the earth exceeds the amount
  of radiation received from the sun, which
  commonly occurs at night, or during the winter
  when the angle of the sun is very low in the sky.

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And what are the Causes of Temperature Inversion?

• This effect is virtually confined to land regions
  as the ocean retains heat far longer. In the
  Polar Regions during winter, inversions are
  nearly always present over land.
• A warmer air mass moving over a cooler one can
  "shut off" any convection which may be present in
  the cooler air mass. This is known as a capping
  inversion.

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And what are the Causes of Temperature Inversion?

• However, if this cap is broken, either by extreme
  convection overcoming the cap, or by the lifting
  effect of a front or a mountain range, the sudden
  release of bottled-up convective energy like the
  bursting of a balloon can result in severe
  thunderstorms.

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And what are the Effects of Temperature Inversion?

• With the ceasing of convection, which is normally
  present in the atmosphere, a number of phenomena
  are associated with a temperature inversion. The
  air becomes stiller hence the air becomes murky
  because dust and pollutants are no longer lifted
  from the surface.
• This can become a problem in cities where many
  pollutants exist

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Where does this frequently occur?

• Inversion effects occur frequently in big cities
  such as Mumbai, India Los Angeles, California
  Mexico City  Sao Paulo, Brazil Santiago, Chile
  and Tehran, Iran, but even also in smaller cities
  like Oslo, Norway and Salt Lake City.

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Santiago. Chile
Los Angeles, California
Mexico City
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And what are the Effects of Temperature Inversion?

• Sometimes the inversion layer is higher so that
  the cumulus clouds can condense but then they
  spread out under the inversion layer. This cuts
  out sunlight to the ground and prevents new
  thermals from forming. A period of cloudiness is
  followed by sunny weather as the clouds disperse.
  This cycle can occur more than once in a day.

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And what are the Effects of Temperature Inversion?

• In addition, when an inversion layer is present
  (for example early in the morning when
  ground-level air temperatures are cool, and high
  level air temperatures are warmer), if a sound or
  explosion occurs at ground level, the sound wave
  can travel much further than normal- the sound is
  refracted by the temperature change at the
  boundary and it undergoes total internal
  reflection. Much of the sound is thus trapped
  under the layer and the sound can travel much
  greater distances than normal.

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And what are the Effects of Temperature Inversion?

• In an inversion, vertical motion in the
  atmosphere is suppressed because the atmosphere
  is stable. Hence vertical heat transport by
  eddies is suppressed this reduced (downwards)
  heat transport leads to further cooling of the
  lower surface. This can lead to an effective
  decoupling of the atmosphere from the surface in
  extreme conditions, such as may be found in
  Antarctica during the polar night, where
  inversions greater than 25 C commonly occur.

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And what are the Effects of Temperature Inversion?

• If a transmitting antenna extends into such a
  duct of cool air, or if the radio wave enters the
  duct at a very low angle of incidence, vhf and
  uhf transmissions may be propagated far beyond
  normal line-of-sight distances. When ducts are
  present as a result of temperature inversions,
  good reception of vhf and uhf television signals
  from a station located hundreds of miles away is
  not unusual.

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And what are the Effects of Temperature Inversion?

• These long distances are possible because of the
  different densities and refractive qualities of
  warm and cool air. The sudden change in density
  when a radio wave enters the warm air above a
  duct causes the wave to be refracted back toward
  Earth. When the wave strikes the Earth or a warm
  layer below the duct, it is again reflected or
  refracted upward and proceeds on through the duct
  with a multiple-hop type of action.

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Bibliography

• http//en.wikipedia.org/wiki/Temperature_inversion
  
• http//www.weatherquestions.com/What_is_a_temperat
  ure_inversion.htm
• http//www.komotv.com/weather/asksteve/4348226.htm
  l

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