wolkendraden

Wolkendraden is a term used in atmospheric science to describe filamentous, thread-like structures that appear within certain cloud systems. The word combines wolk (cloud) and draden (threads). In observational literature, wolkendraden refer to slender streaks or filaments that extend across cloud fields and often run roughly parallel to the prevailing wind direction. They are typically observed in high- or mid-level clouds such as cirrus or cirrostratus, though similar filamentary features can occur in stratocumulus under shear.

Formation and appearance: Wolkendraden arise from microphysical and dynamical processes that organize ice crystals or water droplets into elongated filaments. Wind shear and stable layering favor alignment and stretching of cloud elements, producing fine filaments that may persist from minutes to hours. The contrast between filaments and surrounding cloud depends on optical thickness and particle phase, giving them a delicate, thread-like appearance.

Observation and methods: Detection relies on high-resolution satellite imagery, ground-based lidar, and aircraft or drone photography. In studies, wolkendraden are analyzed as indicators of wind shear, moisture transport, and cloud microphysics, contributing to radiative transfer by changing local albedo and scattering properties.

Usage and status: Internationally, wolkendraden is not a widely standardized term, and usage varies. It is more common in Dutch-language meteorological literature and in popular science writing as a descriptive label for cloud-thread structures.

See also: cloud filament, wind shear, cirrus, cloud streets, radiative effects of clouds.