The maximum parcel level (MPL) is the highest level in the

atmosphere An atmosphere () is a layer of gas or layers of gases that envelop a planet, and is held in place by the gravity of the planetary body. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A s ...

that a moist convectively rising

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 constan ...

will reach after ascending from the

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

(LFC) through the

free convective layer In atmospheric sciences, the free convective layer (FCL) is the layer of conditional or potential instability in the troposphere. It is a layer in which rising air can experience positive buoyancy (PBE) so that deep, moist convection (DMC) can occ ...

(FCL) and reaching the

equilibrium level In meteorology, the equilibrium level (EL), or level of neutral buoyancy (LNB), or limit of convection (LOC), is the height at which a rising parcel of air is at the same temperature as its environment. This means that unstable air is now stable ...

(EL), near the

tropopause The tropopause is the atmospheric boundary that demarcates the troposphere from the stratosphere; which are two of the five layers of the atmosphere of Earth. The tropopause is a thermodynamic gradient-stratification layer, that marks the end of ...

. 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 (), or upthrust, is an upward force exerted by a fluid that opposes the weight of a partially or fully immersed object. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus the p ...

. Because of this, the EL is approximately the region where the distinct flat tops (called anvil clouds), often observed around the upper portions of

cumulonimbus cloud Cumulonimbus (from Latin ''cumulus'', "heaped" and ''nimbus'', "rainstorm") is a dense, towering vertical cloud, typically forming from water vapor condensing in the lower troposphere that builds upward carried by powerful buoyant air currents. ...

s. If the air parcel ascended quickly enough then it retains

momentum In Newtonian mechanics, momentum (more specifically linear momentum or translational momentum) is the product of the mass and velocity of an object. It is a vector quantity, possessing a magnitude and a direction. If is an object's mass an ...

after it has cooled and continues rising past the EL, ceasing at the MPL (visually represented by the

overshooting top An overshooting top (or penetrating top) is a dome-like protrusion shooting out of the top of the anvil of a thunderstorm and into the lower stratosphere. When an overshooting top is present for 10 minutes or longer, it is a strong indication that ...

, above the anvil). Dynamic processes within and between convective cells, such as updraft merging and

cloud base A cloud base (or the base of the cloud) is the lowest altitude of the visible portion of a cloud. It is traditionally expressed either in metres or feet above mean sea level or above a planetary surface, or as the pressure level corresponding to ...

areal size, factor into the actual ultimate cloud top height, in addition to

atmospheric thermodynamics Atmospheric thermodynamics is the study of heat-to-work transformations (and their reverse) that take place in the earth's atmosphere and manifest as weather or climate. Atmospheric thermodynamics use the laws of classical thermodynamics, to descr ...

of the MPL. Updraft merging can lead to higher cloud tops thus an implication is that organized convection can be taller convection.

External links

Skew-T: A Look at MPL

The Difference between the Equilibrium Level and Maximum Parcel Level

(

San Francisco State University San Francisco State University (commonly referred to as San Francisco State, SF State and SFSU) is a public research university in San Francisco. As part of the 23-campus California State University system, the university offers 118 different b ...

)

References

Atmospheric thermodynamics Severe weather and convection {{Climate-stub fr:Niveau d'équilibre convectif#Notions dérivées

See also

External links

References