Frost

   The mornings recently have been beautiful, with frost collecting on wires, trees, bushes and other plants. But what exactly are we looking at? Here is some information we gathered from the internet.

  Hoar frost and rime ice tend to look virtually the same until you get an up-close look. The main difference between the two lies in the source of the moisture.

  Hoar frost typically develops on cold, clear nights when the water vapor in the air comes into contact with solid surfaces that are below the freezing point. Lightweight ice crystals then begin to form, and the ice continues to grow as more water vapor is frozen. The size of the frost that forms depends on how much water vapor is available to feed the ice crystals as they grow. Hoar frost forms hair-like or feathery structures as it grows. When there is little to no wind, this allows for more complex lacy deposits of crystals to form.

  Rime ice comes from freezing fog; water droplets that turn directly from a liquid state to a solid state, or through direct freezing. So rime ice is more like accumulating freezing dew rather than thick frost, and often looks more like icy needles pointing off of objects. The icy needles may point in one direction if driven by the wind. Rime ice is heavier and can last for several days, build up over time, and cause broken tree branches and power lines.

  One Des Moines television weatherman commented that what he saw was rime ice because there was fog.  —photos by TJ Turner