Ice Crystals Blowing in the Wind

Photo copyright by Craig Johnson Weather Briefing, LC. Photo at Cedar Falls, Iowa.

Cirrus clouds often create fall streaks containing ice crystals. These streaks can fill the sky with streamers like we see in this photo. The crystals are heavy enough to fall toward the ground, pulled by gravity that overcomes the slight upward motions that created the cirrus in the first place. These crystals do not reach the ground, however, if the crystals fall into lower clouds made of water droplets the crystals can seed the clouds with ice nuclei that encourage the growth of more ice or water droplets in the lower clouds. Those crystals or droplets may fall to earth as snow or rain.

Photo copyright by Craig Johnson, Weather Briefing, LC. at Cedar Falls, Iowa

This photo shows the fall streaks from a different angle. Ice crystals do not evaporate to become water vapor. Instead, the crystals will sublimate in dry air. That means they turn from a solid (ice) to water vapor directly without first become water droplets. Sublimation happens more slowly than evaporation so cirrus can be smeared long distances across the sky with strong winds aloft. That is what gives some cirrus to look of strands of hair that help give the cloud its name.