Maximum parcel level
Encyclopedia
The maximum parcel level (MPL) is the highest level in the atmosphere
that a moist convectively
rising air parcel
will reach after ascending through the free convective layer
(FCL) and reaching the equilibrium level
(EL), near the tropopause
. As the parcel rises through the FCL it expands adiabatically causing its temperature to drop, often below the temperature of its surroundings, and eventually lose buoyancy
. Because of this, the EL is approximately the region where the distinct flat tops (called anvil
s) often observed on cumulonimbus cloud
s form. If the air parcel ascended quickly enough then it retains momentum
after it has cooled and continues rising past EL, ceasing at the MPL (visually represented by the overshooting top
, above the anvil).
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...
that a moist convectively
Convection
Convection is the movement of molecules within fluids and rheids. It cannot take place in solids, since neither bulk current flows nor significant diffusion can take place in solids....
rising 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...
will reach after ascending through the free convective layer
Free convective layer
In atmospheric sciences, the free convective layer is the layer of conditional or potential instability in the troposphere. It is a layer of positive buoyancy and is the layer where deep, moist convection can occur. On an atmospheric sounding, it is the layer between the level of free...
(FCL) and reaching 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), near the tropopause
Tropopause
The tropopause is the atmospheric boundary between the troposphere and the stratosphere.-Definition:Going upward from the surface, it is the point where air ceases to cool with height, and becomes almost completely dry...
. As the parcel rises through the FCL it expands adiabatically causing its temperature to drop, often below the temperature of its surroundings, and eventually lose buoyancy
Buoyancy
In physics, buoyancy is a force exerted by a fluid that opposes an object's weight. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus a column of fluid, or an object submerged in the fluid, experiences greater pressure at the bottom of the...
. Because of this, the EL is approximately the region where the distinct flat tops (called anvil
Anvil
An anvil is a basic tool, a block with a hard surface on which another object is struck. The inertia of the anvil allows the energy of the striking tool to be transferred to the work piece. In most cases the anvil is used as a forging tool...
s) often observed on cumulonimbus cloud
Cumulonimbus cloud
Cumulonimbus is a towering vertical cloud that is very tall, dense, and involved in thunderstorms and other inclement weather. Cumulonimbus originates from Latin: Cumulus "Heap" and nimbus "rain". It is a result of atmospheric instability. These clouds can form alone, in clusters, or along a cold...
s form. If the air parcel ascended quickly enough then it retains momentum
Momentum
In classical mechanics, linear momentum or translational momentum is the product of the mass and velocity of an object...
after it has cooled and continues rising past EL, ceasing at the MPL (visually represented by the overshooting top
Overshooting top
An overshooting top is a dome-like protrusion that shoots out of the top of the anvil of a thunderstorm. When an overshooting top is present for 10 minutes or longer, it is a strong indication that the thunderstorm may be severe....
, above the anvil).