Construction of the EMC^2 Instrument Object

The emc2.core.Instrument object contains all of the information that is needed for EMC^2 to both visualize instrument data as well as the instrument specific parameters that are needed to simulate a lidar or a radar.

It is recommended that you use class inheritance to make your own Instrument objects. This helps to ensure that your object has the required methods for EMC^2 to use. For example, the object for the High Spectral Resolution Lidar is created as follows:

$ class HSRL(Instrument):
$     def __init__(self):
$         """
$         This stores the information for the High Resolution Spectral Lidar.
$         """

Make sure all of the variables are initalized and the proper wavelength is entered:

$         super().__init__(wavelength=0.532 * ureg.micrometer)

Define whether your instrument is a lidar or a radar:

$         self.instrument_class = "lidar"

Name your instrument:

$         self.instrument_str = "HSRL"

If it’s a lidar, we’ll tell EMC^2 to consider the signal to be extinct above a certain optical depth:

$         self.ext_OD = 4

If we have a radar, we will assign the dielectric constant. Since this is a lidar, we will assign NaN to K_w:

$         self.K_w = np.nan

Tell EMC^2 what the index of refraction of water is:

$         self.eps_liq = (1.337273 + 1.7570744e-9j)**2

The rest of these parameters are needed if you are specifying a radar:

$         self.pt = np.nan
$         self.theta = np.nan
$         self.gain = np.nan
$         self.Z_min_1km = np.nan
$         self.lr = np.nan
$         self.pr_noise_ge = np.nan
$         self.pr_noise_md = np.nan
$         self.tau_ge = np.nan
$         self.tau_md = np.nan

In addition, the mie tables for each hydrometeor class must be specified:

$         # Load mie tables
$         data_path = os.path.join(os.path.dirname(__file__), 'mie_tables')
$         self.mie_table["cl"] = load_mie_file(data_path + "/MieHSRL_liq.dat")
$         self.mie_table["pl"] = load_mie_file(data_path + "/MieHSRL_liq.dat")
$         self.mie_table["ci"] = load_mie_file(data_path + "/MieHSRL_ci.dat")
$         self.mie_table["pi"] = load_mie_file(data_path + "/MieHSRL_pi.dat")

Addition of more wavelengths - format of Mie tables

If you wish to use an instrument with a different wavelength than what is currently used in EMC^2, then you must generate the Mie scattering parameters using your favorite Mie scattering code for the given wavelength. The mie scattering tables are xarray datasets with the following variables:

Variable	Description
wavelength	The wavelength \(\lambda\) of the beam in microns.
p_diam	The diameter \(D\) of the particle in microns
size_parameter	The size parameter of the particle. This is defined as \(\frac{\pi D}{\lambda}\).
compre_real	Real part of complex index of refraction of the sphere.
compre_im	Imaginary part of complex index of refraction of the sphere
scat_p	Forward scattering cross section in \({\mu m}^2\).
alpha_p	Back scattering cross section in \({\mu m}^2\).
beta_p	Extinction cross section in \({\mu m}^2\).
scat_eff	Scattering efficiency
ext_eff	Extinction efficiency
backscatt_eff	Backscattering efficiency

These mie tables must be generated for the four precipitation classes.