Atmospheric science – definitions:\r What is the correct name for the pressure exerted by fully saturated air (air at 100% relative humidity at a given temperature)?

Introduction / Context:
Moist air properties are central to hydrometeorology and evaporation estimates. At a given temperature, there is a maximum pressure that water vapour can exert in equilibrium with liquid water; this concept is crucial for psychrometrics and mass-transfer evaporation formulas.

Given Data / Assumptions:

• Air is saturated (relative humidity = 100%).
• We seek the standard term for the vapour’s equilibrium pressure at this state.

Concept / Approach:
When air is fully saturated, the water vapour’s partial pressure reaches its temperature-dependent maximum. This maximum is called saturation vapour pressure, often also referred to simply as saturation pressure (of water vapour) at that temperature.

Step-by-Step Reasoning:
Partial pressure refers to any constituent’s share of total pressure; for saturated air, the water vapour’s partial pressure equals its saturation value.Therefore the correct technical names in this saturated condition are “saturation vapour pressure” and “saturation pressure”.

Verification / Alternative check:
Psychrometric charts and Clausius–Clapeyron based tables list saturation vapour pressure versus temperature, confirming established terminology.

Why Other Options Are Wrong:

• “Partial pressure” and “vapour pressure” are generic; they do not specifically emphasize the saturated condition.
• Only the paired terms explicitly denote the maximum at saturation.

Common Pitfalls:

• Using “vapour pressure” generically when the context is specifically the saturated state.
• Confusing total atmospheric pressure with the vapour’s partial pressure.

Final Answer:
Both saturation vapour pressure and saturation pressure