![]() ![]() For formation, all fogs (and clouds) also need tiny nuclei (like dust or smog particles), on which condensation can form. What weather conditions must exist for fog to form? Fog forms when very moist air (air with high humidity) is cooled to its dew point or saturation point, where it can no longer hold the moisture it contains. ![]() The same thing happens, on a larger scale, to make fog. As the water vapor in the atmosphere hits the cold container, it cools, and little beads of water form on the outside of the container. You have seen this if you've left a cold container out on your kitchen counter before. As water vapor cools, it undergoes a process called condensation, where it changes from a gaseous state to a liquid state. In this Cyberchase episode on PBS KIDS GO!, watch as the CyberSquad investigates dew point in order to complete a rescue mission under the cover of fog!įrom where do the water droplets come? They originate from water vapor, which is water in its gaseous state. So when there are enough water droplets suspended in the air, all close together, and you can't see beyond 1 kilometer (km), then you have the weather event called fog. The water droplet is opaque, which means that you can't see through it. Fog! What is fog? Well, imagine a water droplet suspended in the air, like a party balloon that has lost most of its helium and is floating just above the ground. As a side note, the same process can cause freezing rain or drizzle.Here's a riddle for you: What do you call a cloud that sits on the ground? A cloud with a bad altitude? Nope. As a result, any object the freezing fog comes into contact with will become coated with ice, which makes freezing fog very dangerous for travel and walking. If this happens, water droplets remain in the liquid state until they come into contact with a surface upon which they can freeze. The term supercooled, means that the droplets have been cooled beyond the freezing point of 32° F. Freezing fog occurs when the water droplets that the fog is composed of are “ supercooled“. This means that advection fog can be distinguished from radiation fog by its horizontal movement along the ground.Įvery once in a while central Illinois will see this type of fog during the winter. This type of fog is very close to radiation fog, but instead of forming due to a reduction in surface temperature, it forms because of the horizontal movement, or advection of warm/moist air over a cold surface. This type of fog is usually the one responsible for reducing visibility to near zero at night & during the morning, which make driving conditions very hazardous. Radiation fog is nearly stationary and varies in depth, it can be anywhere from 3 to 1,000 feet high and always originates at the ground. As the earth’s surface continues to cool and there is enough moist air present near the ground, the humidity will reach 100% and fog will form. The light winds keep the air from mixing allowing it to cool faster so some of the heat absorbed by the earth’s surface during the day is radiated back into the atmosphere. This type of fog forms during the night under clear skies with light winds. There are two types of fog most common here in central Illinois. For example, rain can cool and the moisten the air near the ground until fog forms or when the sun sets and temperatures at night decrease, fog may develop within a humid air mass. Fog on the other hand cools in different ways. The difference between the two is that clouds usually form from rising air, which cools and expands as it rises. Clouds and fog are similar since they are both made up of condensed water droplets, which is the result of the air being cooled to the point (called the Dew point) where it can no longer hold all of the water vapor it contains. The processes which cause it to form are somewhat different from the way actual clouds form. Fog is considered a cloud at ground level. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |