thermionics is a form of upwind, which results from the fact that sun exposure warms up the earth's surface and in consequence air at the soil. The thermionics, scientifically convection mentioned and transported as „air conditioning system “ of the atmosphere in the course of the day of the sun warmed up airinto larger heights and brings at the same time cooler air from several hundred meters height to the ground.Mountain climbers feel this upwind often with the afternoon descent as warm head wind from the valley, engineless fliers such as sail fliers, kite and paraglider fliers estimate it asso-called „beard “for elevator production. Thermionics is among other things responsible for the emergence of Talwinden, in extreme form they are well-known also as a dust devil (Dust Devils).
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Thermionics needs sun exposure and a suitable ground condition for the emergence sufficiently. There air particularly in an unstably laminated atmosphere easily ascends andthereby first over the drying-adiabatic temperature gradients , it cools down can reach sometime the condensation level and come it to the emergence of clouds. Cumuluswolken are thus a visible sign for thermionics. If air is to drying, so that no Wolkenbildung occurs, speaksone of blue thermionics - the sky remains cloudless and blue. It can be recognized if necessary by along-ascending Pollen, dust as well as circling birds or gliders. In contrast to it cumulonimbus clouds and thunderstorms can form with appropriate thermionics strength from Cumuluswolken in the course of the day.
Often „“the developed thermionics a slope flows along close-towards-set to the drop line upward up to an outline edge - this can be a break in the area or a change of the ground condition. There the warm air package separates from the soil and rises howa large Seifenblase up. In the flat country more easily moderate wind helps with the fact to that it can separate and ascend at area edges or edges of forest from the soil.
The thermal upwind ends, if from the soil no further warm air flows. Depending upon sun exposure can some time last, until again sufficient warm air developed and these again ascend can. With these recurring upwinds in same place one speaks of pulsating thermionics.
factors of the thermionics intensity
the intensity of the thermionics hangs among other things of the sun exposure, the condition of the earth's surface, the air humidity and the irradiation angle off. A dry Getreidefeld can deliver more warmth than a damp meadow, one toSun bent mountain flank is warmed up more than the flat country. This is because of the different retention of heat as well as humidity and evaporation of the underground. The ideal thermionics soil should
- reflect if possible little sunlight (small albedo value),
- little water evaporate and
- little warmth into thatSoil derive, but hot will, in order to warm up air over it.
The soil warmth continues to lead downward (e.g. ), He warms up to loamy soil only little. A bad heat leader, like dry sand or a plowed field, heats itself against it.A wet soil derives warmth faster into the depth. Likewise a large part of the solar power is used up, warmed up by evaporation accordingly more weakly near-surface air. Plants can reduce dependent on its kind, Wachstumsstand and density the thermionics. ThatForest plays thereby a special case: During the day it reduces the thermionics by evaporation, against evening is however warmer the crown area than the environment and donates a weak thermionics. On the other hand clearings and edges of forest are good sources of thermionics and outline edges. The soil stores muchWarmth, like e.g. Forests or cities, he can deliver her temporally transferred air and leads to thermionics in the late afternoon until evening.
On the other hand the temperature gradient (vertical temperature decrease) of the ambient air plays for the intensity of a thermal upwinda substantial role, which can amount to between 0,65° C and 1,35° C per 100 m height. There the warm air when ascending up to reaching the condensation level constantly with 1° C per 100 m (drying-adiabatic temperature gradient) cools down, resembles themselves theirTemperature difference with gradients under 1° C (stable layering) with increasing height the ambient air on weak thermionics with removing climb values the consequence is fast. With gradients of 1° C (indifferent layering) the temperature difference with increasing height remains the sameand leads to more moderate to good thermionics with continuous climb values. If the gradient over 1° C (unstable layering) amounts to, the temperature difference with the height takes according to likewise increases the climb values and thermionics strength.
Therefore itself those can with cool air advectionThermionics substantially strengthen. It occurs, if cooler air masses in higher air layers are caused by another place like e.g. after the passage a Kaltfront, that so-called. Back weather. Thus already small heating up of the soil is sufficient, around thatwarmed up air a temperature projection/lead in relation to the ambient air to give and a separation and a rapid ascending to cause. Such weather conditions are used by thermionics fliers gladly to expanded en-route flights.
Further effects support the upwind:
With the emergence of clouds additionally condensation warmth is set free,to a further temperature projection/lead to the environment and thus to further ascending of the Luftpakete to lead can - the thermionics strengthens.
In the edge zones of the upwinds by Entrainment dry and cooler air is interfered. Straight one with dampness convection, thus, The thermionics can strengthen thermionics clouds still further by developing evaporative cold, since a thin cool air coat puts around the cloud.
in the Aviatik is measured the strength of the thermionics as speed of ascending air. This amounts tobetween 0,5 up to 10 meters/second, on the average 1 to 5 meters/second. As measuring instrument the rate of climb indicator serves.
The spatial distribution of the thermionics in the atmosphere can be measured also as follows:
- Measurement of the wind field (by Doppler shift) by means of different radar technologies, RADAR, LIDAR, SODAR
- indirect measurement of the temperature distribution of an air volume by measurement of the heat radiation (infrared). From the temperature distribution can be concluded on the thermionics
by thermal upwinds to become possibly. It moves ions whereby the electrical field of the atmosphere changes.The measurement of the electrical field respectable. its gradient within the air volume (from an airplane) are possibly indikativ for the presence of thermionics.
in the engineless Fliegerei, for example with the Segelflug, hanging sliding and paraglider flies, becomesThermionics used, in order to win height (1,000 to 3,000 meters in the flat country, in the mountains still more highly). The upper, usable border of the thermionics is the cloud basis. Disturbing for the Motorfliegerei however the thermionics is rather, there it unpleasant turbulences to cause can.
Thermionics power stations try to convert the energy contained in the thermionics into electricity.