The freezing fog resulted in a stunning display of the scenery across the area this morning, while the trees were covered with ice.
Was that frost or frost? That is a big question that we have been asked. The difference between the two has to do with changing the physical phase of the water.
Rime Ice
Creamy ice is caused by a phase change from supercooled liquid water to ice. I explained what super-cooled water is in a blog post last night. You can read it here.
Many clouds (and last night’s fog) are composed of droplets of liquid water that exist in sub-zero temperatures. Temperatures were well below zero last night, which meant that when these drops of super-cooled liquid water came into contact with solid objects below freezing, they froze.
So this morning’s icy trees were the result of freezing ice through dense freezing fog. Freezing fog is the main cause of ice.
Ice can be hard or soft and usually depends on the strength of the wind. A stronger wind will result in hard frost, which looks thicker and more compact in soft frost. Soft frost can appear more fragile and feathered and resemble frost.
Hoar Frost
Frost is caused by a phase change from the gaseous water vapor directly to the ice when the air reaches the freezing point through cooling. It is similar to dew, but when temperatures are below freezing. It is not the liquid dew that freezes. This type of frost usually occurs on a cold, clear and calm night in the presence of sufficient humidity.
