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

atmosphere An atmosphere () is a layer of gases that envelop an astronomical object, held in place by the gravity of the object. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A stellar atmosph ...

that a moist convectively rising air parcel 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 (FCL) and reaching the equilibrium level (EL), near the

tropopause The tropopause is the atmospheric boundary that demarcates the lowest two layers of the atmosphere of Earth – the troposphere and stratosphere – which occurs approximately above the equatorial regions, and approximately above the polar regi ...

. 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 the force exerted by a fluid opposing the weight of a partially or fully immersed object (which may be also be a parcel of fluid). In a column of fluid, pressure increases with depth as a result of the weight of t ...

. 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 () 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. Above the lower portions of the cumulonimbus the water ...

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

momentum In Newtonian mechanics, momentum (: momenta or momentums; 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. ...

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 Atmospheric thermodynamics is the study of heat-to-Work (physics), 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 thermodyn ...

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 (San Francisco State, SF State and SFSU) is a Public university, public research university in San Francisco, California, United States. It was established in 1899 as the San Francisco State Normal School and is ...

)

References

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

See also

External links

References