My last two musings have been about Antarctica and atmosphere. Specifically I have talked about fog. I think most people think about fog as simply being in a cloud with no sense of space and just a vast gray darkness. Certain monuments like the Golden Gate Bridge are typically associated with fog but there are truly many different types of fog and they are all visually different.
The different types of fog, include Radiation Fog, Precipitation Fog, Advection fog, Steam Fog, Upslope Fog, Valley Fog, Freezing Fog and Ice Fog.
Radiation Fog: This fog forms when all solar energy exits the earth and allows the temperature to meet up with the dew point. A lot of times this type of fog is associated with rain. The ground is soaked and laden with moisture. This makes it easier for the air to become saturated and form fog. However, for fog to form after a rain there is typically no wind which accentuates the drying process and limits the fog.
Precipitation Fog: This is fog that forms when rain is falling through cold air. This is common with a warm fronts but it can occur with cold fronts colliding with a warm front. Cold air, dry at the surface while rain is falling through it evaporates and causes the dew point to rise. This saturation forms fog.
Advection Fog: This type of fog forms from surface contact of horizontal winds. This fog can occur with windy conditions. Warm air, moist air blows in and if there is snow or cool moisture on the ground it will come in contact with the warm, moist winds. This contact between the air and ground will cause the air blowing in to become cool. Then dew point rises and creates high humidity and forms fog.
Steam Fog: This type of fog is commonly seen over bodies of water. As summer ends, water temperatures don’t cool right away but air temperature does. As a mass of dry, cold air moves over a warmer lake the warm lake conducts warm, moist air into the air mass above. Steam fog does not become very deep but enough to block some of the sunlight.
Upslope Fog: This fog forms adiabatically. Adiabatically is the process that causes sinking air to warm and rising air to cool. As moist winds blow toward a mountain, the wind glides up and this causes the air to rise and cool. The cooling of the air from rising causes to meet up with the dew point temperature. Fog forms on top of the mountains.
Valley Fog: Valley fog forms in the valley when the soil is moist from previous rains. As the skies clear solar energy exits earth and allow the temperature to cool near or at the dew point. This form deep fog, so dense it’s sometimes called tule fog.
Freezing Fog: Freezing fog occurs when the temperature falls at 32°F (0°C) or below. This fog produces drizzle and these tiny droplets freeze when they come into contact with an object.
Ice Fog: This type of fog is only seen in the polar and artic regions. Temperatures at 14 F (-10°C) is too cold for the air to contain super-cooled water droplets so it forms small tiny ice crystals.