Foreign Direct Investment (FDI) from the viewpoint of the Balance of Payments and the. International Investment Position (IIP) share a same conceptual framework given by the. International Monetary Fund (IMF).
The dew point is the temperature at which the water vapor in the air can no longer stay in a vapor form, and condenses from a vapor into a liquid on a surface. The film of air around the mug in the picture cools rapidly due to the cold temperature of the surface of the glass.
The answer is because temperature sets a limit to how much water vapor can be in the air. Even in tropical air, once the volume of water vapor in the atmosphere approaches 4% it will begin to condense out of the air (rain). The condensing of water vapor prevents the percentage of water vapor in the air from increasing. If temperatures were much warmer, there would be a potential to have more than 4% water vapor in the atmosphere. Think about the steam trapped in a tea kettle.