Abstract
A laboratory experiment was initiated to grow the banded columnar crystals found in cirrus clouds and to determine if they nucleated through a freezing nucleus. Banded columnar crystals were collected in cirrus clouds and also grown in a laboratory cold box over a temperature range of −20 to −46C. They were observed to grow from a frozen droplet through several distinct crystalline transitions. The first distinct crystalline form observed following the growth of a frozen droplet was a polyhedral crystal. With further growth, the polyhedral crystal developed end plates, and it appeared to be a “double plate.” Then the separation between the plates nearly filled in to leave the characteristic band. Certain columns (−6 to −10C) and plates (−10 to −20C) were also observed to grow from a frozen droplet and showed similar crystalline transitions.
