Convection
Convection is the concerted, collective movement of groups or aggregates of molecules within fluids (e.g., liquids, gases) and rheids, through advection or through diffusion or as a combination of both of them. Convection of mass cannot take place in solids, since neither bulk current flows nor significant diffusion can take place in solids. Diffusion of heat can take place in solids, but that is called heat conduction. Convection can be demonstrated by placing a heat source (e.g. a Bunsen burner) at the side of a glass full of a liquid, and observing the changes in temperature in the glass caused by the warmer ghost fluid moving into cooler areas.
Convective heat transfer is one of the major types of heat transfer, and convection is also a major mode of mass transfer in fluids. Convective heat and mass transfer take place both by diffusion – the random Brownian motion of individual particles in the fluid – and by advection, in which matter or heat is transported by the larger-scale motion of currents in the fluid. In the context of heat and mass transfer, the term "convection" is used to refer to the sum of advective and diffusive transfer. In common use the term "convection" may refer loosely to heat transfer by convection, as opposed to mass transfer by convection, or the convection process in general. Sometimes "convection" is even used to refer specifically to "free heat convection" (natural heat convection) as opposed to forced heat convection. However, in mechanics the correct use of the word is the general sense, and different types of convection should be qualified for clarity.
Atmospheric convection
Atmospheric convection is the result of a parcel-environment instability, or temperature difference, layer in the atmosphere. Different lapse rates within dry and moist air lead to instability. Mixing of air during the day which expands the height of the planetary boundary layer leads to increased winds, cumulus cloud development, and decreased surface dew points. Moist convection leads to thunderstorm development, which is often responsible for severe weather throughout the world. Special threats from thunderstorms include hail, downbursts, and tornadoes.
Overview
There are a few general archetypes of atmospheric instability that correspond to convection and lack thereof. Steeper and/or positive lapse rates (environmental air cools quickly with height) suggests atmospheric convection is more likely, while weaker and/or negative environmental lapse rates suggest it is less likely. This is because any displaced air parcels will become more (less) buoyant, given their sign of adiabatic temperature change, in the steep (weak) lapse rate environments.
Podcasts:
Convection
ALBUMS
- Orkus Compilation 61 released: 2010
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by Deicide
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by Primal Fear
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by Crucified
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by The Crucified
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by Amber Pacific
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by Hate
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by In Fear & Faith
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by Question Mark
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by Breeze
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by Crimson Armada
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by Contravene
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by Storyteller
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by Leaders
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by As Bold As Lions
Conviction
by: DeicideA day of death upon the cross of deceit
impure with pleasure to bare witness to he
death calling you to christ, human sacrifice, conviction
down the unseen, your belief, absent god, don't exist
go unto thou, from the dead, walk with him, he ain't there
love in retreat, uncompelled, feel no pain, pray unfelt
hate run in place, holy grace, contemplate, there's no god
the work of jesus was the devil in fact
his miracles were nothing more than a trap
lies pinned upon the cross, crucify his false religion
conviction, choking on the crucifix in his blood
conviction, take the bullet for the love of a son
conviction, from the cross into his kingdom you go
conviction, no more bullshit from the likes of the lord
satanic visions bring the lord to his death
their own disenchantment of perversions confessed
caught, harrow in disgust, revel in your lost religion
conviction, choking on the crucifix in his blood
conviction, take the bullet for the love of a son
conviction, from the cross into his kingdom you go