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than the surrounding air. The lighter air rises and cools due to its expansion in the lower pressure at higher altitudes. It stops rising when it has cooled to the same temperature, thus density, as the surrounding air.
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into visible droplets. When a steady wind is present, thermals and their respective cumulus clouds can align in rows oriented with wind direction, sometimes referred to as "
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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.
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169:(LFC), rising to great heights, condensing large quantities of water and forming convective clouds causing showers or even thunderstorms. The latter are
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at the top of the thermal. Cumulus clouds are formed by the rising air in a thermal as it ascends and cools, until the
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Thermal cross section with stronger lift (rising air) in darker shades of green, while red is sink (descending air).
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warms the ground, which in turn warms the air directly above. The warm air near the surface expands, becoming less
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can prevent thermals from rising high and the air is said to be stable, as mature thermals can't form.
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Bubble or vortex ring thermal model (left), and column or plume thermal model (right)
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of thermals are influenced by the properties of the lower atmosphere (the
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energy allowing the air to rise higher. Very unstable air can reach the
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Meteorology and Flight: Pilot's Guide to
Weather (Flying & Gliding)
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208:, carrying dust instead of water vapor. Thermals are also seen on the
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This article is about the atmospheric phenomenon. For other uses, see
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Time-lapse video of clouds caused by thermals forming and decaying
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Thermals are often indicated by the presence of visible isolated
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Column of rising air in the lower altitudes of Earth's atmosphere
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282:. U.S. Dept. of Transportation, FAA. 2003. pp. 9–6, 9–7
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Example of a thermal column between the ground and a cumulus
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Thermals are also seen elsewhere in the solar system. On
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173:to any aircraft flying through or nearby.
273:"Glider Flying Handbook, FAA-H-8083-13A"
176:Thermals are one of the many sources of
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334:Thermal Structure and Behavior
161:The condensing water releases
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370:Severe weather and convection
330:What do thermals look like?
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355:Atmospheric thermodynamics
231:Atmospheric thermodynamics
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280:FAA government handbooks
167:level of free convection
83:, and are an example of
21:Thermal (disambiguation)
301:Bradbury, Tom (2000).
89:atmospheric convection
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196:Thermals beyond Earth
142:in the air begins to
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360:Aviation meteorology
336:by Wayne M. Angevine
305:. A & C Black.
365:Gliding technology
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284:. Retrieved
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246:Hang gliding
214:Bénard cells
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226:Air current
206:dust devils
163:latent heat
140:water vapor
121:troposphere
349:Categories
286:21 January
259:References
85:convection
171:dangerous
158:pilots.
126:inversion
220:See also
180:used by
144:condense
116:strength
241:Gliding
186:gliders
152:soaring
133:cumulus
77:thermal
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156:glider
136:clouds
276:(PDF)
150:" by
105:dense
307:ISBN
288:2021
202:Mars
190:soar
184:and
178:lift
154:and
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75:(or
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210:sun
188:to
101:Sun
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