Nuvols

Nuvols, in Catalan, are the visible masses of condensed water vapour or ice crystals suspended in the Earth's atmosphere. They form when moist air rises, cools, and water vapour condenses around tiny particles called condensation nuclei. Their appearance and altitude reflect atmospheric conditions and the processes lifting air.

Clouds are commonly grouped by altitude and form. High clouds include cirrus, cirrostratus, cirrocumulus; mid-level clouds include altostratus and altocumulus; low-level and vertically developing clouds include stratus, stratocumulus, cumulus, and cumulonimbus. Nimbostratus describes rain-bearing, flat layers. Cumulonimbus can develop tall anvils and bring heavy thunderstorms. Many clouds combine features (e.g., altocumulus undulatus; stratocumulus castellanus).

They form by convection, frontal lifting orographic uplift. They are indicators of weather patterns; for instance, cirrus can indicate an approaching front; cumulonimbus signals potential thunderstorms; persistent low-level stratus can imply light rain or drizzle.

Clouds affect Earth's energy balance by reflecting sunlight (albedo) and trapping infrared radiation; they are central to the hydrological cycle and climate research. The World Meteorological Organization maintains a standard cloud atlas; genus names (cirrus, cumulus, stratus) describe form, while species and varieties specify height and appearance.