Ilmavettä

Ilmavettä is the Finnish term used to describe the water content present in the air, i.e., water in its gaseous form as part of the atmosphere. In meteorology and climate science this gaseous phase is usually referred to as vesihöyry (water vapor), while "ilmavettä" is a common, everyday expression for humidity or moisture in the air.

In the atmosphere, most of the water exists as vapor rather than liquid. The amount of water vapor the air can hold depends on temperature: warmer air can contain more water vapor. When air cools or becomes saturated, the water vapor can condense into tiny droplets, forming clouds or fog, or it can deposit as frost on surfaces. The transition between gaseous water and liquid or solid water is governed by processes such as evaporation, condensation, sublimation, and deposition.

Humidity is commonly quantified in several ways. Relative humidity expresses the current amount of water vapor as a percentage of the maximum amount the air can hold at a given temperature. Absolute humidity measures the mass of water vapor per volume of air, while specific humidity relates to the mass of water vapor relative to the total mass of air. The dew point is the temperature at which air must be cooled for condensation to begin. Hygrometers and other sensors are used to monitor ilmavettä in weather stations and climate studies.

Ilmavettä plays a central role in weather, climate, and the energy balance of the atmosphere. It influences precipitation, cloud formation, and thermal dynamics, and it affects human comfort and health through conditions of humidity.