Frostdjup

Frostdjup is a neologism used to describe a rapid frost-formation event on exposed surfaces during subfreezing conditions, particularly under calm, clear nights. The term usually refers to frost that accumulates quickly and uniformly, forming a layer that can become visibly thick within a few hours. In practice, frostdjup is more often encountered in speculative or informal discussions about weather than in formal meteorology.

Etymology and origins of the term are not tied to any single scientific source. The word combines “frost” with a form derived from Nordic language roots such as djup, meaning deep, to convey the idea of deep or rapid frost penetration. It emerged in online communities and climate-focused fictional or hypothetical writings in the early 21st century.

Formation and characteristics are described in lay terms rather than through standardized protocols. Key triggers include radiative cooling of surfaces, high relative humidity, and very light or absent wind, all of which favor deposition or riming processes that produce frost quickly. The frost type associated with frostdjup is often hoarfrost or rimed frost, appearing on vegetation, glass, and metal surfaces. The resulting layer tends to be delicate yet visually striking, often with branching crystal patterns. The phenomenon is typically transient, melting away with sunrise or with warming air masses.

In usage, frostdjup appears in climate fiction, speculative scenarios, and some non-peer-reviewed discussions as a descriptive concept to illustrate sudden frost hazards or dramatic cold events. It is not widely adopted as a formal category in current meteorology, where frost formation is described through established processes such as deposition frost, hoarfrost, and riming.

See also: frost, hoarfrost, rime ice, radiative cooling.