The capacity of air to hold water vapor increases with which factor?

• A. Higher air temperature
• B. Lower air temperature
• C. Higher pressure
• D. Increased humidity

Answer: (A)

Warm air can hold more water vapor because the saturation vapor pressure—the maximum amount of moisture the air can contain before condensation—rises with temperature. As air heats up, molecules move faster and stay in the gaseous phase even with more water present, increasing the air’s capacity. Cooler air can’t support as much moisture before it condenses, so its capacity is lower. Humidity, by contrast, is simply how much water vapor is actually in the air, not how much it could hold. Pressure has less influence on this capacity under typical flight conditions, since the key limit is temperature.