nattavkjøling

Nattavkjøling, also known as nocturnal cooling or night sky radiation, is a natural process where surfaces exposed to the night sky lose heat through infrared radiation. This phenomenon is most effective on clear, dry nights with minimal wind. The ground and objects on it radiate thermal energy upwards into space, especially during periods of low atmospheric moisture, which can trap heat.

The rate of nattavkjøling depends on several factors, including the surface material, its temperature, and the atmospheric conditions. Dark, matte surfaces tend to radiate heat more effectively than light or reflective surfaces. Cloud cover acts as a blanket, reflecting some of the outgoing infrared radiation back towards the surface and reducing the cooling effect. Similarly, wind can mix the air, bringing warmer air from higher altitudes down to the surface and mitigating the cooling.

This process is important in various contexts. In meteorology, it contributes to the formation of dew and frost when surfaces cool below the dew point of the surrounding air. In architecture and urban planning, understanding nattavkjøling can inform strategies for passive cooling in buildings and urban environments, particularly in hot climates where dissipating built-up heat is a concern. By allowing buildings and paved surfaces to cool down overnight, the overall heat load during the following day can be reduced.