Ice crystals are solid ice exhibiting atomic ordering on various length scales and include hexagonal columns, hexagonal plates, dendritic crystals, and diamond dust. The highly symmetric shapes are due to depositional growth, namely, direct deposition of water vapour onto the ice crystal. Depending on environmental temperature and humidity, ice crystals can develop from the initial hexagonal prism into numerous symmetric shapes. Possible shapes for ice crystals are columns, needles, plates and dendrites. If the crystal migrates into regions with different environmental conditions, the growth pattern may change, and the final crystal may show mixed patterns. An example are capped columns. Ice crystals tend to fall with their major axis aligned along the horizontal, and are thus visible in polarimetric weather radar signatures with enhanced (positive) differential reflectivity values. Electrification of ice crystals can induce alignments different from the horizontal. Electrified ice crystals are also well detectable by polarimetric weather radars.
Temperature and water vapor humidity determine crystalline forms. Ice crystals are responsible for various atmospheric optics displays.
Ice clouds are composed of ice crystals, the most notable being cirrus clouds and ice fog. The slight whitening of a clear blue sky caused by ice crystals high in the troposphere can be a sign that a weather front (and rain) is approaching, as moist air is carried to high levels and freezes to ice crystals.
Read more about Ice Crystals: Geometry
Famous quotes containing the words ice and/or crystals:
“I know the ice in your drink is senile.
I know your smile will develop a boil.
You know only that you are on top,
swinging like children on the money swing....”
—Anne Sexton (1928–1974)
“It is clear that everybody interested in science must be interested in world 3 objects. A physical scientist, to start with, may be interested mainly in world 1 objects—say crystals and X-rays. But very soon he must realize how much depends on our interpretation of the facts, that is, on our theories, and so on world 3 objects. Similarly, a historian of science, or a philosopher interested in science must be largely a student of world 3 objects.”
—Karl Popper (1902–1994)