The convective condensation level (CCL) represents the height (or pressure) where an
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, ...
becomes
saturated when heated from below and lifted
adiabatically due to buoyancy.
In the atmosphere, assuming a constant water vapor mixing ratio, the dew point temperature (the temperature where the
relative humidity is 100%) decreases with increasing height because the pressure of the atmosphere decreases with height. The CCL is determined by plotting the dew point (100%RH) versus altitude and locating the intersection with the actual measured temperature sounding. It marks where the
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 ...
begins when air is heated from below to the
convective temperature The convective temperature (CT or Tc) is the approximate temperature that air near the surface must reach for cloud formation without mechanical lift. In such case, cloud base begins at the convective condensation level (CCL), whilst with mechanica ...
, without mechanical lift.
Once the CCL is determined, the surface temperature necessary to raise a mass of air to that height can be found by using the
Dry Adiabatic Lapse Rate (DALR) to determine the potential temperature. In the early morning, this temperature is typically larger than the surface temperature, in the mid-afternoon, it may be the same.
Compare this to the
Lifting Condensation Level
The lifted condensation level or lifting condensation level (LCL) is formally defined as the height at which the relative humidity (RH) of an air parcel will reach 100% with respect to liquid water when it is cooled by dry adiabatic lifting. The ...
(LCL) where the air is lifted and cooled without first increasing the surface temperature. The LCL is less than or equal to the CCL depending on the temperature profile.
Both condensation levels indicate the altitude (or pressure) where relative humidity reaches 100%. However, since the actual condensation level depends on the availability of condensation nuclei, clouds typically do not form until the relative humidity is somewhat above 100%.
See also
*
Atmospheric convection
Atmospheric convection is the result of a parcel-environment instability, or temperature difference layer in the atmosphere. Different lapse rates within dry and moist air masses lead to instability. Mixing of air during the day which expands the ...
*
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 des ...
*
Lifting condensation level
The lifted condensation level or lifting condensation level (LCL) is formally defined as the height at which the relative humidity (RH) of an air parcel will reach 100% with respect to liquid water when it is cooled by dry adiabatic lifting. The ...
and
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.
...
References
External links
SKEW-T: A LOOK AT CCLConvective condensation level (CCL)(Glossary of Meteorology)
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Severe weather and convection
Atmospheric thermodynamics