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Example of a thermal column between the ground and a cumulus
This article is about the atmospheric phenomenon. For other uses of the term thermal, see thermal (disambiguation).


A thermal column (or thermal) 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 are an example of convection. The Sun warms the ground, which in turn warms the air directly above it.

When a pool of warmer air accumulates, it expands and becomes lighter (less dense) than the surrounding air mass. The mass of lighter air will then rise, but as it does so it will cool due to expansion. This process will continue until at some height the pool of air will have cooled to the same temperature as the surrounding air, at this stage the air will stop rising. Also associated with a thermal is a downward flow surrounding the thermal column. The downward moving exterior is caused by colder air being displaced at the thermal top.

The size and strength of thermals are influenced greatly by the properties of the lower atmosphere (the troposphere). Generally, when the air is cold, bubbles of warm air formed by the ground heating the air above it, can rise like a hot air balloon. The air is then said to be unstable. If there is a warm layer of air higher up, an inversion can prevent thermals from rising high and the air is said to be stable.

Thermals are often indicated by the presence of visible cumulus clouds. When a steady wind is present thermals and their respective cumulus clouds can align in rows oriented with wind direction. Cumulus clouds formed by the rising air in a thermal as it cools and ascends, until the water vapor in the air begins to condense into visible droplets. The condensing water releases latent heat energy allowing the air to rise higher. Very unstable air can rise to great heights condensing large quantities of water and so forming showers or even thunderstorms.

Thermals are one of the many sources of lift used by soaring birds and gliders to soar.

See also

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Thermal can mean:
  • Clothing worn in extreme cold to conserve body heat
  • Exothermic reaction in chemistry
  • Heat
  • Thermal, California, a small town near Indio, California
  • Thermal neutron

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Air or Earth's atmosphere is a layer of gases surrounding the planet Earth.

Air may also refer to:
  • Air (1977 video game), an air combat based mainframe computer game
  • Air (band), a French electronic music duo

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Earth's atmosphere is a layer of gases surrounding the planet Earth and retained by the Earth's gravity. It contains roughly (by molar content/volume) 78% nitrogen, 20.95% oxygen, 0.93% argon, 0.
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Solar radiation is radiant energy emitted by the sun from a nuclear fusion reaction that creates electromagnetic energy. The spectrum of solar radiation is close to that of a black body with a temperature of about 5800 K.
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Convection in the most general terms refers to the movement of currents within fluids (i.e. liquids, gases and rheids).

Convection is one of the major modes of heat and mass transfer.
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In physics, density is mass m per unit volume V—how heavy something is compared to its size. A small, heavy object, such as a rock or a lump of lead, is denser than a lighter object of the same size or a larger object of the same weight, such as pieces of
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The word size may refer to how big something is. In particular:
  • Measurement
  • Dimensions: length, width, height, diameter, perimeter, area, volume
  • Clothing sizes such as shoe size or dress size
  • Body dimensions

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In physics, power (symbol: P) is the rate at which work is performed or energy is transmitted, or the amount of energy required or expended for a given unit of time.
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not to scale.]]

The troposphere is the lowest portion of Earth's atmosphere. It contains approximately 75% of the atmosphere's mass and almost all of its water vapor and aerosols.

The average depth of the troposphere is about 11 km in the middle latitudes.
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inversion is a deviation from the normal change of an atmospheric property with altitude. It almost always refers to a temperature inversion, i.e., an increase in temperature with height, or to the layer within which such an increase occurs.
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cloud is a visible mass of condensed droplets, frozen crystals suspended in the atmosphere above the surface of the Earth or another planetary body, such as a moon. (Clouds can also occur as masses of material in interstellar space, where they are called interstellar clouds and
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Water vapor or water vapour (see spelling differences), also aqueous vapor, is the gas phase of water. Water vapor is one state of the water cycle within the hydrosphere.
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Condensation is the change in matter of a substance to a denser phase, such as a gas (or vapor) to a liquid.[1] Condensation commonly occurs when a vapor is cooled to a liquid, but can also occur if a vapor is compressed (i.e.
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In thermochemistry, latent heat is the amount of energy in the form of heat released or absorbed by a substance during a change of phase (i.e. solid, liquid, or gas), - also called a phase transition.
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Not to be confused with lift (force).


Lift, or more precisely "static lift" is rising air used by soaring birds and by humans in gliding, hang gliding and paragliding to make extended soaring flights.
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This is a list of types of soaring birds, which are birds that can maintain flight without wing flapping, using rising air currents. Many gliding birds are able to 'lock' their extended wings by means of a specialized tendon.
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Gliders or Sailplanes are heavier-than-air aircraft primarily intended for unpowered flight. See also gliding and motor gliders for more details.[1]

Terminology

A "glider" is an unpowered aircraft.
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Gliding is a recreational activity and competitive sport in which pilots fly un-powered aircraft known as gliders or sailplanes. Properly, the term gliding refers to descending flight of a heavier-than-air craft, whereas soaring
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A "hot tower" is a tropical cumulonimbus cloud that penetrates the tropopause, i.e. it reaches out of the lowest layer of the atmosphere, the troposphere, into the stratosphere. In the tropics, the tropopause typically lies at least 15 km above sea level.
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An updraft or downdraft (air pocket) is the vertical movement of air as a weather related phenomenon. Commonly, one of two forces causes the air to move. Localized regions of warm or cool air will exhibit vertical movement.
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atmosphere is a layer of gases that may surround a material body of sufficient mass.[1] The gases are attracted by the gravity of the body, and are retained for a longer duration if gravity is high and the atmosphere's temperature is low.
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