Edit filter log

'{{One source|date=July 2009}} [[Image:Thermal column.svg|thumb|Example of a thermal column between the ground and a cumulus]] {{about|the atmospheric phenomenon|other uses of the term '''thermal'''|thermal (disambiguation)}} YOUR HEADTEACHER IS GAYYYYYYYYYYY!!!!!!!!!!! '''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 an example of [[convection]]. The Sun warms the ground, which in turn warms the air directly above it.<ref>{{cite book |last= Bradbury |first= Tom |title= Meteorology and Flight: Pilot's Guide to Weather (Flying & Gliding) |publisher= A & C Black |year= 2000 |id = ISBN 0-7136-4226-2}}</ref> Dark earth, urban areas and roadways are good sources of thermals. The warmer air expands, becoming less [[density|dense]] than the surrounding air mass. The mass of lighter air rises, and as it does, it cools due to its expansion at lower high-altitude pressures. It stops rising when it has cooled to the same temperature as the surrounding air. 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 top of the thermal. The [[size]] and [[power (physics)|strength]] of thermals are influenced by the properties of the lower atmosphere (the ''[[troposphere]]''). Generally, when the air is cold, bubbles of warm air are formed by the ground heating the air above it and 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 [[temperature inversion|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 cloud|cumulus]] [[clouds]] at the apex of the thermal. When a steady wind is present thermals and their respective cumulus clouds can align in rows oriented with wind direction, sometimes referred to as "cloud streets" by [[soaring]] and [[Glider (sailplane)|glider]] pilots. Cumulus clouds are formed by the rising air in a thermal as it ascends and cools, 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 reach the [[level of free convection]] (LFC) and thus 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 (soaring)|lift]] used by [[soaring birds]] and [[Unpowered aircraft|gliders]] to [[gliding|soar]]. Thermals on the [[sun]] typically form hexagonal prisms ([[Bénard cell]]s). ==References== {{Reflist}} ==External links== *[http://www.rcsoaring.com/docs/thermals_2006.pdf What do thermals look like?] - ''Thermal Structure and Behavior'' by Wayne M. Angevine *[http://bookergc.blogspot.com/2008/04/thermal-formation-and-decay.html Time-lapse video of clouds caused by thermals forming and decaying] [[Category:Aviation terminology]] [[Category:Aeronautics]] [[Category:Weather]] [[Category:Convection]] [[da:Termik]] [[de:Thermik]] [[es:Térmica]] [[eo:Termiko]] [[fr:Bulle de convection]] [[id:Termal]] [[it:Corrente ascensionale]] [[he:זרם אוויר חם]] [[hu:Termik]] [[nl:Thermiek]] [[no:Termikk]] [[nn:Termikk]] [[pl:Komin termiczny]] [[ru:Термик]] [[sl:Termika]] [[fi:Termiikki]] [[sv:Termik]] [[uk:Термальна колона]]'