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. ...
that a moist
convectively rising
air parcel will reach after ascending from the
level of free convection (LFC) 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
Adiabatic (from ''Gr.'' ἀ ''negative'' + διάβασις ''passage; transference'') refers to any process that occurs without heat transfer. This concept is used in many areas of physics and engineering. Notable examples are listed below.
A ...
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
A cumulonimbus incus (Latin ''incus'', "anvil"), also known as an anvil cloud, is a cumulonimbus cloud which has reached the level of stratospheric stability and has formed the characteristic flat, anvil-top shape. It signifies the thunderstor ...
), often observed around the upper portions of
cumulonimbus clouds. If the air parcel ascended quickly enough then it retains
momentum after it has cooled and continues rising past the EL, ceasing at the MPL (visually represented by the
overshooting top, above the anvil).
Dynamic processes within and between convective cells, such as updraft merging and
cloud base areal size, factor into the actual ultimate cloud top height, in addition to
atmospheric thermodynamics of the MPL. Updraft merging can lead to higher cloud tops thus an implication is that organized convection can be taller convection.
See also
*
Atmospheric convection
*
Skew-T log-P diagram
External links
Skew-T: A Look at MPLThe Difference between the Equilibrium Level and Maximum Parcel Level(
San Francisco State University)
References
Atmospheric thermodynamics
Severe weather and convection
{{Climate-stub
fr:Niveau d'équilibre convectif#Notions dérivées