Free convection level

Diagram showing the path of an air parcel when ascending along the line BCE compared to the ambient air with temperature (T) and humidity / humidity temperature (Tw)

The level of free convection ( NFK ) is the altitude in the atmosphere at which the temperature of the environment decreases more with altitude than that of a saturated air parcel, i.e. the cloud particle under consideration, along the state curve with a moist adiabatic temperature gradient .

The usual technique to find the NFK is to lift a package (particle) from a lower level along the dry adiabatic until it intersects the line of constant (moisture) mixing ratio at point B : this is the uplift condensation level (HKN , English Lifting Condensation Level, LCL ). From there, follow the humid adiabats until the temperature of the package reaches the air temperature in the (so-called) equilibrium level (EL). The level of free convection ( NFK = LFC) has been found at point (C), from which the temperature of the parcel along the moisture adiabats becomes / is warmer than that of the surroundings with further (forced) uplift .

Since a volume of the same mass of the considered parcel from point C ( NFK = LFC) is greater than that of the surrounding air (due to the law for ideal gases : PV = nRT), the ascending parcel is less dense and is lifted freely / independently until its temperature (for E or EL ) is equal to that of the surrounding air. If the examined air mass has one or more NFK = LFC, it is potentially unstable; this can lead to convective clouds such as cumulus or cumulonimbus and, accordingly, to thunderstorms .

See also

• Convective inhibition ( English Convective inhibition, CIN )
• Convective Available Potential Energy (CAPE)
• Condensation level # Free convection level

Web links

• SKEW-T: A LOOK AT LFC (English)
• Level of free convection (LFC) (Glossary of Meteorology)