Level of free convection
Encyclopedia
The level of free convection (LFC) is the altitude in the atmosphere
where the temperature
of the environment decreases faster than the moist adiabatic lapse rate of a saturated air parcel
at the same level.
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 mixing ratio line of the parcel: this is the lifted condensation level
(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.
Since the volume of the parcel is larger than the surrounding air after LFC by the ideal gas law
(PV = nRT), it is less dense and becomes buoyant rising until its temperature (at E) 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 thunderstorm
s.
Earth's atmosphere
The atmosphere of Earth is a layer of gases surrounding the planet Earth that is retained by Earth's gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention , and reducing temperature extremes between day and night...
where the temperature
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
of the environment decreases faster than the moist adiabatic lapse rate of a saturated air parcel
Air parcel
In fluid dynamics, within the framework of continuum mechanics, a fluid parcel is a very small amount of fluid, identifiable throughout its dynamic history while moving with the fluid flow. As it moves, the mass of a fluid parcel remains constant, while—in a compressible flow—its volume may...
at the same level.
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 mixing ratio line of the parcel: this is the lifted condensation level
Lifted condensation level
The lifted condensation level or lifting condensation level is formally defined as the height at which the relative humidity of an air parcel will reach 100% when it is cooled by dry adiabatic lifting...
(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
Equilibrium level
In meteorology, the equilibrium level , or level of neutral buoyancy , or limit of convection , is the height at which a rising parcel of air is at a temperature of equal warmth to it....
(EL). If the temperature of the parcel along the moist adiabat is warmer than the environment on further lift, one has found the LFC.
Since the volume of the parcel is larger than the surrounding air after LFC by the ideal gas law
Ideal gas law
The ideal gas law is the equation of state of a hypothetical ideal gas. It is a good approximation to the behavior of many gases under many conditions, although it has several limitations. It was first stated by Émile Clapeyron in 1834 as a combination of Boyle's law and Charles's law...
(PV = nRT), it is less dense and becomes buoyant rising until its temperature (at E) equals the surrounding airmass. If the airmass has one or many LFC, it is potentially unstable and may lead to convective clouds like cumulus
Cumulus cloud
Cumulus clouds are a type of cloud with noticeable vertical development and clearly defined edges. Cumulus means "heap" or "pile" in Latin. They are often described as "puffy" or "cotton-like" in appearance. Cumulus clouds may appear alone, in lines, or in clusters...
and thunderstorm
Thunderstorm
A thunderstorm, also known as an electrical storm, a lightning storm, thundershower or simply a storm is a form of weather characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere known as thunder. The meteorologically assigned cloud type associated with the...
s.
External links
- SKEW-T: A LOOK AT LFC
- Level of free convection (LFC) (Glossary of Meteorology)