Fog is defined as water droplets suspended in the air at the Earth’s surface. To make it simple, fog is the same as a cloud, it is just very close to the ground.
Water droplets form when air is cooled and converted into water vapor. It is this interaction of the warm and cold that creates the environment needed for the droplets to develop.
This episode of weather for kids will talk about the different types of fog we experience through the year. Each type is created a little different, but the fog develops due to the interaction/change in the temperature of the air and the amount of moisture available at the time.
Below are the different types of fog:
Steam Fog – Colder air moves over a warmer body of water. The water evaporates adding moisture to the air. This layer of air is warmed by the water near the surface. As it rises it turns to vapor and looks like steam.
Radiation Fog – This happens at night when the temperature cools down. Dry in the atmosphere can trap moisture near the ground. The outgoing radiation from the Earth passes through this layer as it escapes toward space at night. The moist layer does not absorb much heat and it cools faster than the air above. As the moisture rises into the cooler layer, it turns into a vapor, and fog forms.
Upslope Fog – Cold air is forced up the side of a mountain or high terrain. It becomes colder. Moisture forms in the process and fog forms on the side of the mountain or high terrain.
Precipitation Fog – Warm air moves in with rain. The rain evaporates into the cooler layer below the shower. The evaporation process causes the air to become even cooler. Moisture saturates near the surface and the rain moves away with the shower. This moisture becomes fog.
Advection Fog – Onshore winds blow in warmer air over colder water. The warm air gets cooled by the water loaded with moisture. Fog forms in the process. The wind continues to blow the warmer air and fog inland.
*Advection fog also happens over land. We see this during the Winter with a snowpack on the ground. The warmer air moves in over the cold snow and fog forms.