Thelevel of free convection (LFC) is the altitude in theatmosphere where anair parcel lifted adiabatically until saturation becomes warmer than the environment at the same level, so that positive buoyancy can initiate self-sustained convection.[1]
The usual way of finding the LFC is to lift a parcel from a lower level along thedry adiabatic lapse rate until it crosses the saturated mixing ratio line of the parcel: this is thelifted condensation level (LCL). From there on, follow themoist adiabatic lapse rate until the temperature of the parcel reaches the air mass temperature, at theequilibrium level (EL). If the temperature of the parcel along the moist adiabat is warmer than the environment on further lift, one has found the LFC.[2][3]
Since the volume of the parcel is larger than the surrounding air after LFC by theideal gas law (PV = nRT), it is less dense and becomes buoyant rising until its temperature (at EL) equals the surrounding airmass. If the airmass has one or many LFC, it is potentially unstable and may lead to convective clouds likecumulus andcumulonimbus clouds.
From the level of free convection to the point where the ascending parcel again becomes colder than its surroundings, theequilibrium level (EL), any air parcel gain kinetic energy which is calculated by itsConvective available potential energy (CAPE), giving the potential forsevere weather.[4]
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