Basic use

Import

First, you need import the package cra as follows:

from metpy.units import units
from cra.air_sounding import AirSounding
from cra.variables import VariablesSet

Load file and define variables

The file must be formatted in a CSV-like format.

Note

To open ftr and cor files please see the last section.

Note

VariablesSet uses pandas.read_csv to open files.

You can load it with VariablesSet:

v_set = VariablesSet('my_file.csv', delimiter=';')

All keywords arguments will be given to pandas.read_csv so please refer to the pandas documentation if you have any problems opening a file.

Once the file is open, you can define the variables in it. Basically, you should define:

  • the pressure

  • the temperature

  • the dew point (this can also be calculated from temperature and relative humidity)

  • the east wind component

  • the north wind component

To do this you need to use the predefined methods:

v_set.add_press(('Press', units.hPa))  # Press is the name of the pressure in the file
v_set.add_temp(('T_air', units.degC))  # T_air is the name of the temperature in the file
v_set.add_windu(('WE', units('m/s'))
v_set.add_windv(('WN', units('m/s'))

In this exemple, the file does not contain the dew point so we have to calculate it:

v_set.compute_dewpoint(('T_air', units.degC), ('RelU', units.percent))

Here 'RelU' is the name of the relative humidity in the file.

Plots data

Once all the variables are defined, we can create a new instance of AirSounding:

air_souding = AirSounding(v_set)

and plot the upper air sounding on a Skew-T diagram:

air_sounding.show()

You can also try to find some layers into the upper air sounding:

air_sounding.auto_layers(nb_layers=15, show=True)

Handle ftr and cor files

This package also provide a module to simply handle ftr and core files. You can import it as follows:

from cra.files import open_ftr, open_cor

You just need to give to the opening function the name of the file and the keywords argument to be given to pandas.read_csv:

v_set = open_ftr('myfile.ftr', delimiter='\t')