Pilvipäällyste

Pilvipäällyste refers to a phenomenon where clouds cover a significant portion of the sky. This covering can range from a thin veil of cirrus clouds to a thick, opaque layer of stratus or cumulonimbus clouds. The extent and type of pilvipäällyste significantly influence surface temperature, visibility, and the amount of solar radiation reaching the ground.

Different types of clouds contribute to pilvipäällyste. High-level clouds like cirrus, cirrostratus, and cirrocumulus, composed mainly of ice crystals, can create a partial or thin covering, often resulting in halos around the sun or moon. Mid-level clouds such as altostratus and altocumulus can produce a more substantial covering, potentially leading to light precipitation. Low-level clouds like stratus and stratocumulus are responsible for extensive, often uniform overcast conditions, which are commonly associated with drizzly or light rain. Cumulonimbus clouds, known for their vertical development, can also contribute to extensive pilvipäällyste during thunderstorms, bringing heavy rain, hail, and lightning.

The presence of pilvipäällyste affects diurnal temperature variations. During the day, clouds can block incoming solar radiation, leading to cooler temperatures than a clear day. Conversely, at night, clouds act as an insulating layer, trapping outgoing terrestrial radiation and resulting in warmer temperatures compared to clear nights. Visibility can also be reduced under dense pilvipäällyste, particularly when associated with fog or mist. Understanding pilvipäällyste is crucial in meteorology for weather forecasting, aviation, and climate studies.