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definition thermo_parcel_path(vector t, vector td, vector p, definition start_conditionoptions)

definition thermo_parcel_path(netcdf profile, definition start_conditionoptions)

Computes the path of an ascending thermodynamic parcel with the given start condition for the given vertical profile. It returns a definition containing all the data to plot parcel path, buoyancy areas and related data into a thermodynamic diagram. The vertical profile is either specified as a set of vectors where:

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• • profile: the result of a vertical profile extraction from GRIB or BUFR with the thermo_grib() or thermo_bufr() functions (see Thermo Data ), respectively.

There are four different modes to specify the a parcel's start_condition  (as a definition):

The function can take an optional options argument (it is a definition) to specify the various settings for the parcel computations. The members of this definition are as follows (temperature values are in °C and pressure values are in hPa:

• • mode: the start condition mode the possible values are 'surface', 'custom', 'mean_layer' and 'most_unstable' (see  below for details)
  • start_t: the start temperature (see  below for details)
  • start_td: the start dewpoint (see  below for details)
  • start_p: the start pressure (see  below for details)
  • top_p: the top pressure of the start layer (see below for details)
  • bottom_p: the bottom pressure of the start layer (see below for details)
  • stop_at_el: if it is defined and set to 1 the parcel computations will stop at the Equilibrium Level.

There are four different modes available for the parcel start conditions:

Surface

The parcel ascends from the surface, i.e. the lowest point of the profile. The format is as follows:

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The parcel ascends from a given temperature, dewpoint and pressure. The format is as follows:

(mode: 'custom', start_t: start_temperature, start_td: start_dewpoint, start_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', top_p_top: layer_top, bottom_p_bottom: layer_bottom )

Please note that when bottom_p_bottom is omitted the layer starts at the surface.

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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', top_p_top: layer_top, bottom_p_bottom: layer_bottom )

Please note that when bottom_p_bottom is omitted the pressure layer starts at the surface.

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