air hoar

...Ice formed when the temperature near the ground drops below 0°C, when water vapor in the air sublimes directly on the surface of trees or objects, or when supercooled cloud particles attach to and freeze. Depending on how it is formed, it can be classified as tree frost, snow rime, or rough ice. (1) Snow rime: Needle-, plate-, or dendritic ice crystals that form on trees and other objects mainly due to the sublimation of water vapor. They tend to grow on the windward side of objects and trees on clear winter nights when the temperature near the ground drops due to radiative cooling. (2) Snow rime: White, opaque, and brittle ice with a thin, fan-shaped base that freezes instantly when supercooled cloud particles collide with cold trees and objects one after another. It is sometimes called a "shrimp tail" because of its shape. ...

*Some of the terminology that mentions "air hoar" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…主として地表付近の気温が0℃以下になったとき，樹木や地物の表面に大気中の水蒸気が直接昇華したり，または過冷却雲粒が付着し凍結してできた氷。でき方によって，樹霜，樹氷，粗氷に分けられる。(1)樹霜air hoar　おもに水蒸気の昇華によって樹木などにできる針状，板状，樹枝状をした氷の結晶。冬の晴れた夜，地面近くが放射冷却によって気温が下がったときに地物や樹木の風上側に成長しやすい。(2)樹氷soft rime　おもに過冷却雲粒が冷たい樹木や地物に次々に衝突し，瞬間的に凍った白色不透明の根元が細く扇形のもろい氷で，その形から〈えびのしっぽ〉と呼ばれることがある。…

※「air hoar」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報