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A cloud base (or the base of the cloud) is the lowest altitude of the visible portion of a cloud. It is traditionally expressed either in metres or feet above mean sea level or above a planetary surface, or as the pressure level corresponding to this altitude in hectopascals (hPa, equivalent to the millibar ).
The convective temperature (CT or T c) is the approximate temperature that air near the surface must reach for cloud formation without mechanical lift. In such case, cloud base begins at the convective condensation level (CCL), whilst with mechanical lifting (such as from low-pressure areas located in the lower troposphere, frontal systems, surface boundaries, gravity waves, and convergence ...
When there is mechanical lift to saturation, cloud base begins at the lifted condensation level (LCL); absent forcing, cloud base begins at the convective condensation level (CCL) where heating from below causes spontaneous buoyant lifting to the point of condensation when the convective temperature is reached.
The convective condensation level (CCL) represents the height (or pressure) where an air parcel becomes saturated when heated from below and lifted adiabatically due to buoyancy. In the atmosphere, assuming a constant water vapor mixing ratio, the dew point temperature (the temperature where the relative humidity is 100%) decreases with ...
If a thunderstorm forms, then as it grows and matures, processes such as increased saturation at lower levels from precipitation and lower surface pressure usually lead to a lowering of the cloud base. Finally, the LCL can also be considered in relation to the level of free convection (LFC). A smaller difference between the LCL and LFC (LCL-LFC ...
the cloud IR emissivity, with values between 0 and 1, with a global average around 0.7; the effective cloud amount, the cloud amount weighted by the cloud IR emissivity, with a global average of 0.5; the cloud (visible) optical depth varies within a range of 4 and 10. the cloud water path for the liquid and solid (ice) phases of the cloud particles
Convective cloud's thickness, between its base and top, shown on the background scale at different stages of its life. The cloud height, more commonly known as cloud thickness or depth, is the distance between the cloud base and the cloud top. [1]
The lifted index can be used in thunderstorm forecasting, however, convective available potential energy (CAPE) is considered by most as a superior measurement of instability and is preferred by many meteorologists for convection forecasting. [1]