Fog

Condensed water vapor in cloudlike masses lying close to the ground and limiting visibility.

Explanation

Fogs form similar to the way that clouds form, and they are basically just a cloud on the surface of land or water with millions of tiny water droplets. Land fogs usually form in autumn and winter, when the nights are long. There are several different ways that fog can form, depending on the conditions. Below is a description of the different types. Also, you can look at the experiment below to create your own fog.

• Advection Fog: A current of relatively warm, moist air passes over a colder body of land or water. This type is frequent in the winter when snow is on the ground, and is also common over the ocean.
• Radiation Fog: Only formed over land. When radiation lowers water temperature slowly at night, but land is cooling quickly, a fog is formed because of the temperature difference. This fog isn't very thick and usually disappears in the morning when the sun comes up.
• Upslope Fog: Air is evenly cooled by its rising and expanding, such as when a wind flows up a mountain slope, and a fog is formed.
• Precipitation Fog: The snow or rain in a storm cloud passes through a layer of air that is cooler than the precipitation.

What You'll Need:

• beaker
• water
• stove
• ice

Directions:

1. Boil the water on the stove with the help of an adult.
2. Fill the beaker with the boiling water and let it sit for a few minutes.
3. Pour out the water, leaving a couple inches at the bottom.
4. Put a chunk of ice at the mouth of the beaker.
5. Let it sit for several minutes and observe what happens.

What's Happening?

As the warm moist air expands in the beaker, it hits the cool air from the ice above. The molecules come together to form droplets of fog. Eventually these small droplets would normally become larger to fall as rain. A natural fog forms when cool air moves over the ground that was heated by the sun. When the sun comes out the next day, the fog soon disappears and the droplets of water are broken back up into molecules of water vapor.

There are many different levels of fog, from the blinding mass to a light covering to light rain. Below is a description of some of the common forms of fog.

• Fog: This can form on sea or land. The density of fog, or the thickness, depends on the number and size of the water droplets in the air. However, the densest fog has a surprisingly low water content.
• Haze: This is a light fog and has even less water than fog does.
• Mist: This is a fog that is almost rain. It is more transparent, with many tiny droplets of water that float or fall to the ground.
• Freezing Fog: Fog droplets freeze on anything they touch because the temperatures are below freezing.