Ukrainian polar explorers from the Akademik Vernadsky station told about a rare phenomenon - scrolls of snow, also called snow rolls, "donuts" or wind snowballs. This was reported on the Facebook page of the National Antarctic Research Center, UNN reports.
Details
These are multi-layered bundles of snow that usually have a void inside. They can be either very small - from a few centimeters in diameter, or quite noticeable - over a meter in diameter, resembling hay bales in a field. This phenomenon is quite rare, in particular for the Antarctic, although it can be found not only here
A number of weather conditions are required for the formation of snow scrolls, which are "built" from two different layers of snow. The lower layer is frozen or covered with ice crust, and it acts as a kind of substrate. The upper layer is fresh, loose and wet and should cover the lower layer but not stick to it.
The air temperature should be close to the melting point of the ice (i.e., slightly above 0°C); the wind force should be such that it moves the snow clumps but does not destroy them.
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Since the snow in the middle of the bundle is fresh and has a low density, it is easily weathered, leaving a hole (sometimes it forms immediately when the snow blanket is wrapped).