Equilibrium level (‚anvil level‘)


As the air in the updraft rises it cools. The cooling is adiabatic, meaning it cools due to expansion as the pressure drops with height. There is virtually no cooling due to heat transfer with the cooler surrounding air. As long as the rising air (parcel) is warmer than the surrounding air it is buoyant. As it reaches ambient temperature it ceases rising, reaching the equilibrium level (EL). This level is also known as the level of neutral buoyancy (LNB) or the limit of convection (LOC).

In other words: equilibrium level is the altitude at which a rising updraft ceases to rise, its air having cooled down to the same temperature as the surrounding air.

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We will take a look at the two different situations:

  • The equilibrium level is the height at which the rising updraft cools to the temperature of the surrounding air
  • The equilibrium level is produced by a temperature inversion, which prevents the updraft from rising further

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