Glaciating in Clouds Over Sparta, Greece
June 01, 2015
Photographer: P. Nikolakakos
Summary Author: P. Nikolakakos; Jim Foster
The photo above showing a sky filled with glaciated mid-level clouds as observed over Sparta, Greece on May 18, 2015. Ice crystals are falling from altocumulus clouds and sublimating in the drier, warmer air just below the cloud level. These clouds consist of supercooled water droplets. When these droplets freeze they grow quite rapidly because the vapor pressure of water vapor over ice is small compared to the vapor pressure of water vapor over liquid water. The resulting ice crystals are heavy enough to fall from the clouds -- as virga.