What is meant by 'super-saturation' in atmospheric terms?

Super-saturation in atmospheric terms refers to a condition where the air contains more water vapor than it can typically hold at a given temperature and pressure, which usually leads to the development of clouds and precipitation. This state generally occurs under conditions where the humidity exceeds 100%, often due to a combination of cooling the air or through processes like lifting that allow the air to hold more water vapor than it normally would at that specific temperature.

The correct answer discusses the concept of excessive condensation nuclei which can play a significant role in the process of super-saturation. When there are ample condensation nuclei present in the atmosphere, they provide surfaces for water vapor to condense upon when the air reaches super-saturation levels. This can facilitate cloud formation and precipitation even when the relative humidity is above the saturation point for pure water vapor.

Other options do not reflect the precise meaning of super-saturation: a balance of water vapor would indicate a stable state below saturation, holding maximum water vapor points to the saturation point rather than exceeding it, and temperature fluctuations do not define the phenomenon of water vapor exceeding saturation, although they can influence humidity and condensation indirectly.