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This Python package calculates the radar backscatter cross-section for snowflakes, including oblate and prolate shapes.
It is applicable to radar wavelengths ranging from 10 to 183 GHz, no longer than ice particle sizes.
First, install the pytmatrix package by following the instructions on its GitHub Wiki.
Then, clone this repository:
git clone https://github.com/ddaaoo123/Radar_Tmatrix.gitIn run_pytmatrix.py:
| Input Variable | Description | Data type |
|---|---|---|
hifreq_vec |
Radar frequencies in GHz. | np.array |
spheroidtype |
For calculating the snowflake mass and volume. 'oblate' or 'prolate' | string |
ice_material |
Gather information regarding the snowflake refractive index. Default: RefractiveIndexMaterial(shelf='main', book='H2O', page='Warren-2008') | function/class |
ar_inv_sel_vec |
Aspect ratio for the snowflakes | np.array |
rad_elev_array |
Radar elevation angles. radar elevation = 90 - incident zenith | np.array |
Dmax |
Snowflake maximum diameter [mm] | np.array |
mD_relation |
Snowflake m–D relationship. Default: 'myown': m = a*D^b | string |
myown_a_array |
a component in m-D relationship. b component is then calculated. Default: b = 3.457 + 0.51*log10(a) based on https://doi.org/10.1175/JAMC-D-16-0222.1 | np.array |
| Variable Name | Description | Units | Dimensions |
|---|---|---|---|
rad_elev |
Radar elevation angle | degrees | rad_elev |
Dmax |
Snowflake maximum dimension | cm | Dmax |
canting_degree |
Canting degree | degrees | canting_degree |
ssrga_cross_section |
SSRGA Radar backscatter cross section | cm² |
rad_elev, Dmax
|
rayleigh_cross_section_h |
Rayleigh backscatter (horizontal polarization) | cm² |
rad_elev, Dmax
|
rayleigh_cross_section_v |
Rayleigh backscatter (vertical polarization) | cm² |
rad_elev, Dmax
|
sigma_co_nocant_h |
T-Matrix backscatter (horizontal, no canting) | cm² |
rad_elev, Dmax
|
sigma_co_nocant_v |
T-Matrix backscatter (vertical, no canting) | cm² |
rad_elev, Dmax
|
sigma_co_cant_h |
T-Matrix backscatter (horizontal, with canting) | cm² |
rad_elev, Dmax, canting_degree
|
sigma_co_cant_v |
T-Matrix backscatter (vertical, with canting) | cm² |
rad_elev, Dmax, canting_degree
|
backscatter_amplitude_matrix_nocant_real |
Real part of scattering amplitude matrix (no canting) | cm |
rad_elev, Dmax, Smat_dim1, Smat_dim2
|
backscatter_amplitude_matrix_nocant_imag |
Imaginary part of scattering amplitude matrix (no canting) | cm |
rad_elev, Dmax, Smat_dim1, Smat_dim2
|
backscatter_amplitude_matrix_cant_real |
Real part of scattering amplitude matrix (with canting) | cm |
rad_elev, Dmax, Smat_dim1, Smat_dim2, canting_degree
|
backscatter_amplitude_matrix_cant_imag |
Imaginary part of scattering amplitude matrix (with canting) | cm |
rad_elev, Dmax, Smat_dim1, Smat_dim2, canting_degree
|
backscatter_amplitude_matrix_nocant |
Complex scattering amplitude matrix (no canting) | cm |
rad_elev, Dmax, Smat_dim1, Smat_dim2
|
backscatter_amplitude_matrix_cant |
Complex scattering amplitude matrix (with canting) | cm |
rad_elev, Dmax, Smat_dim1, Smat_dim2, canting_degree
|
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am: Coefficient ( a ) in the m–D relationship -
bm: Coefficient ( b ) in the m–D relationship -
aspect_ratio: Inverse aspect ratio used in shape modeling
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Leinonen, J., High-level interface to T-matrix scattering calculations: architecture, capabilities and limitations, Opt. Express, vol. 22, issue 2, 1655-1660 (2014), doi: 10.1364/OE.22.001655.
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Leinonen, J., Python code for T-matrix scattering calculations. Available at https://github.com/jleinonen/pytmatrix/.
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M. N. Polyanskiy. Refractiveindex.info database of optical constants. Sci. Data 11, 94 (2024),https://doi.org/10.1038/s41597-023-02898-2
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Gergely, M., and T. J. Garrett (2016), Impact of the natural variability in snowflake diameter, aspect ratio, and orientation on modeled snowfall radar reflectivity, J. Geophys. Res. Atmos., 121, 12,236–12,252, doi:10.1002/2016JD025192.