1.2.3.4. Equilibrium level (‚anvil level‘)

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  • Author: SW101

The equilibrium level is the the height at which the rising updraft cools to the temperature of the surrounding air

In this case the rising and adiabatically cooling updraft eventually ‘runs out of energy’. As the air in the updraft cools down to the temperature of the surrounding air, it looses buoyancy and stops rising. The height at which this happens can be anything from several kilometers to over 10 km high. You can visually discern an updraft that has reached equilibrium level in this case: an updraft which has ceased rising (or is about to) looses its sharp edge and becomes soft. The strongest updrafts rise above the freezing level, and the water droplets rising with the updraft freeze into ice crystals. As the updrafts ceases to rise, the top of it spreads out in a fuzzy, wispy, fibrous edge, forming a Cumulonimbus capillatus.

The updraft rises towards the equilibrium level through Cumulus congestus and Cumulonimbus calvus stages.

The updraft reaches the equilibrium level. The top of the cloud becomes fibrous, as ice crystals form a wispy, fuzzy top. This is a Cumulonimbus capillatus.