lcl()
definition thermo_parcel_path(vector t, vector td, vector p, definition start_condition)
definition thermo_parcel_path(thermo_profile profile, definition start_condition)
Computes the path of an ascending thermodynamic parcel with the given start condition for the given vertical profile. It returns a definition suitable for plotting all the details of the parcel path into a thermodynamic diagram. The vertical profile is either specified as a set of vectors where:
t: the temperature profile (in K or °C)td: the dew point temperature profile (in K or °C)p: the pressure profile (in Pa or hPa)
or as a vertical profile where:
profile: the result of a vertical profile extraction from GRIB or BUFR with the thermo_grib() or thermo_bufr() functions, respectively.
There are four different modes to specify the a parcel's start_condition (as a definition):
Surface
The parcel ascends from the surface, i.e. the lowest point of the profile. The format is as follows:
(mode: 'surface')
Custom
The parcel ascends from a given temperature, dewpoint and pressure. The format is as follows:
(mode: 'custom', t: start_temperature, td: start_dewpoint, p: start_pressure)
Mean layer
The parcel ascends from the mean temperature, dew point and pressure of a given pressure layer. The format is as follows:
(mode: 'mean_layer', p_top: layer_top, p_bottom: layer_bottom )
Please note that when p_bottom is omitted the layer starts at the surface.
Most unstable
The parcel ascends from the most unstable condition. To determine this, a parcel is started from all the points along the profile in the specified pressure layer. The start level of the parcel that results in the highest CAPE value will define the most unstable start condition. The format is as follows:
(mode: 'most_unstable',
p_top: layer_top,
p_bottom: layer_bottom )
Please note that when p_bottom is omitted the pressure layer starts at the surface.
The function returns a definition with several members to describe all th parameters related to the parcel's ascend. These are as follows:
- path: the path of the parcel. It is itself a definition with two members: t and p, each containing a list of values.
- area: the positive and negative buoyancy areas between the parcel path and the profile. It is a list of definitions describing the areas.
- cape: the value of the CAPE (Convective Available Potential Energy) (J/kg)
- cin: value the CIN (Convective Inhibition) (J/kg)
- lcl: the Lifted Condensation Level. It is a definition with two members: t and p. If no LCL exists it is set to nil.
- lfc: the Level of Free Convention. It is a definition with two members: t and p. If no LFC exists it is set to nil.
- el: the Equilibrium Level. It is a definition with two members: t and p. If no EL exists it is set to nil.
- top: the Cloud Top Level. It is defined by the pressure level where the parcel. It is a definition with two members: t and p. If no TOP exists it is set to nil.