Striped clouds, also known as radiatus clouds, are a fascinating meteorological phenomenon appearing as parallel bands or stripes across the sky. This unique cloud formation isn't a specific cloud type itself, but rather a variety that can be observed within several cloud types. The term "radiatus," meaning "striped" in Latin, describes the characteristic parallel arrangement of the clouds, not a distinct cloud formation mechanism.
Types of Radiatus Clouds
Radiatus clouds can be found within five main cloud types:
- Cirrus radiatus (Ci ra): High-altitude, wispy clouds exhibiting a striped appearance.
- Altocumulus radiatus (Ac ra): Mid-altitude, puffy clouds arranged in parallel bands.
- Altostratus radiatus (As ra): Mid-altitude, sheet-like clouds showing parallel striations.
- Cumulus radiatus (Cu ra): Low-altitude, puffy clouds aligned in parallel rows.
- Stratocumulus radiatus (Sc ra): Low-altitude, layered clouds with a striped pattern.
The appearance of these parallel bands is due to various atmospheric conditions, including wind shear and gravity waves. Wind shear, the difference in wind speed and direction at different altitudes, can create these aligned cloud formations. Gravity waves, disturbances in the atmosphere, also contribute to the parallel structure of radiatus clouds. These waves can be generated by mountains (topography) or thunderstorms (atmospheric instability).
Other "Striped" Cloud Appearances
While radiatus describes parallel bands, other cloud formations might also appear striped. For example, undulatus clouds have a wavy, undulating appearance, often in rows. These aren't strictly "striped" in the same sense as radiatus clouds but can create a similar visual effect.
Additionally, phenomena like "roll clouds" and "cloud streets" can present as horizontal lines or stripes across the sky. Roll clouds are single, horizontal, tube-shaped clouds, while cloud streets are multiple roll clouds appearing in a line, creating a street-like pattern. These formations are often associated with atmospheric waves and wind shear.
Causes of Striped Clouds
The underlying cause of the striped appearance in various cloud types stems from consistent atmospheric conditions affecting cloud formation along aligned pathways. The specific details depend on the cloud type and the atmospheric processes involved, but wind shear and gravity waves are frequently implicated.
