On a foggy day, the overnight temperatures were warmer. why is this?
-
Fog is composed of very tiny water droplets (it is a cloud in contact with the ground). These tiny water droplets act to intercept and re-radiate heat energy from the surface in all directions, including back towards the surface. As a result it acts sort of like a blanket, trapping some of the heat and keeping temperatures warmer than they would be otherwise.
-
The ground water is warmer than the air in the evening and rises into the cool night when the sun evaporates the water from the ground it warms the earth and the water is warm and brings the warm fog into the air.
-
Fog creates latent heating