Crystal Fern

by Marnie Patchett

Title

Crystal Fern

Artist

Marnie Patchett

Medium

Photograph - Photograph

Description

Ice crystals form on a stick on top of a frozen lake, they remind me of fern leaves. It was 12 degrees at Castle Lake in Northern California the morning I was out taking pictures.

Ice crystals are solid ice exhibiting atomic ordering on various length scales and include hexagonal columns, hexagonal plates, dendritic crystals, and diamond dust. The hugely 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 humidity determine many different 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.

Uploaded

December 19th, 2016

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