The level of free convection (LFC) is the altitude in the

atmosphere An atmosphere () is a layer of gases that envelop an astronomical object, held in place by the gravity of the object. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A stellar atmosph ...

where an air parcel lifted adiabatically until saturation becomes warmer than the environment at the same level, so that positive buoyancy can initiate self-sustained convection.

Finding the LFC

The usual way of finding the LFC is to lift a parcel from a lower level along the dry adiabatic lapse rate until it crosses the saturated mixing ratio line of the parcel: this is the

lifted condensation level The lifting condensation level or lifted condensation level (LCL) is the height at which the relative humidity (RH) of an air parcel will reach 100% with respect to liquid water when it is cooled by dry adiabatic lifting. The RH of air increases ...

(LCL). From there on, follow the moist adiabatic lapse rate until the temperature of the parcel reaches the air mass temperature, at the equilibrium 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.

Use

Since the volume of the parcel is larger than the surrounding air after LFC by the

ideal gas law The ideal gas law, also called the general gas equation, is the equation of state of a hypothetical ideal gas. It is a good approximation of the behavior of many gases under many conditions, although it has several limitations. It was first stat ...

(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 like cumulus and thunderstorms. From the level of free convection to the point where the ascending parcel again becomes colder than its surroundings, the equilibrium level (EL), any air parcel gain kinetic energy which is calculated by its Convective available potential energy (CAPE), giving the potential for

severe weather Severe weather is any dangerous meteorological phenomenon with the potential to cause damage, serious social disruption, or loss of human life. These vary depending on the latitude, altitude, topography, and atmospheric conditions. High ...

Finding the LFC

Use

References

See also