Cloud base

Cloud base is the lowest level of a cloud or cloud layer, where suspended droplets or ice crystals become visible. Its height depends on atmospheric moisture, temperature, and lifting.

Lifting condensation level: The height at which a rising unsaturated air parcel cools to saturation. It often approximates the cloud base formed by air lifted from the surface.
Ceiling (clouds): The height above ground of the lowest cloud layer reported as broken or overcast, or of vertical visibility into obscuration. Aviation ceilings use the lowest qualifying cloud layer, not every cloud base.
Cloud top: The highest boundary of a cloud or cloud layer. It marks the opposite vertical boundary from cloud base.
Stratus cloud: A low, uniform cloud layer that often covers much of the sky. Its broad, low base commonly forms as moist air cools gradually near the surface.
Dew point: The temperature at which air becomes saturated with water vapor at a given pressure. The temperature gap between air and dew point helps determine how far air must rise before clouds form.
Ceilometer: An instrument that measures cloud-base height, commonly using reflected laser or light pulses. It provides continuous local estimates of cloud-base height for weather and aviation.
Cloud layer: A horizontal region of cloud occupying a range of altitudes in the atmosphere. Cloud base names the lower boundary of this broader atmospheric feature.
Cumulus cloud: A cloud with a detached, rounded outline and a comparatively flat base, often formed by convection. Its base often traces the condensation level of rising thermals.
Adiabatic cooling: A temperature change caused by expansion or compression without heat exchange with the surroundings. Rising air expands and cools, bringing it toward saturation at cloud base.
METAR: A standardized routine report of observed weather at an airport. METAR reports encode cloud amounts and bases that pilots use to assess conditions.

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