Cirrostratus
Topic: Water in the Atmosphere: Humidity, Condensation, Clouds and Precipitation · NCERT: Class 11, Ch 10 "Water in the Atmosphere"
Meaning
Cirrostratus is a high cloud. "Cirro" means high and "stratus" means layered. It is a thin, sheet-like veil of ice crystals spread across the sky. Light passing through the ice crystals bends and makes a halo, a ring of light round the Sun or Moon. Cirrostratus usually comes before a warm front, where warm air slides up over cold air and later brings steady rain.
Example
Over north-western Europe, for example over Britain, a halo round the Moon often appears when a cirrostratus veil spreads in ahead of an Atlantic warm front. Thicker cloud and rain follow.
Don't confuse with
- Altostratus: a lower, thicker grey sheet. The Sun looks dim through it, and it usually shows no halo.
- Cirrus: also a high ice cloud, but it is made of separate feathery streaks, not an even veil.
Related concepts
- Cloud classification by height
- Cirrocumulus
- Altostratus
- Altocumulus
- Stratocumulus
- Nimbostratus
- Cumulonimbus