ppcpy.retrievals.depolarization#

Functions

calc_pdr

Calculate the particle depolarization ratio and estimate its standard deviation.

calc_profile_vdr

Calculate volume depolarization ratio using GHK parameters.

get_MDR

get the vdr at reference height

pardepol_cldFreeGrps

smooth_signal

voldepol_cldFreeGrps

ppcpy.retrievals.depolarization.smooth_signal(signal, window_len)[source]#
ppcpy.retrievals.depolarization.voldepol_cldFreeGrps(data_cube, ret_prof_name)[source]#
ppcpy.retrievals.depolarization.calc_profile_vdr(sigt, sigc, Gt, Gr, Ht, Hr, eta, voldepol_error, window, flag_smooth_before=True)[source]#

Calculate volume depolarization ratio using GHK parameters.

Parameters:#

sigtndarray

Signal strength of the total channel [photon count].

sigcndarray

Signal strength of the cross channel [photon count].

Gtfloat

G parameter in the total channel.

Gcfloat

G parameter in the cross channel.

Htfloat

H parameter in the total channel.

Hcfloat

H parameter in the cross channel.

etafloat

Depolarization calibration constant.

voldepol_errorfloat

Systematic uncertainty coefficient (constant term). Systematic uncertainty coefficient (linear term). Systematic uncertainty coefficient (quadratic term).

smooth_windowint, optional

The width of the sliding smoothing window for the signal. Default is 1.

flag_smooth_beforebool, optional

Flag to control whether smoothing is applied before or after the signal ratio. Default is True.

Returns:#

vol_depolndarray

Volume depolarization ratio.

vol_depol_stdndarray

Uncertainty of the volume depolarization ratio.

References:#

  • Engelmann, R. et al. The automated multiwavelength Raman polarization and water-vapor lidar Polly XT: the neXT generation. Atmospheric Measurement Techniques 9, 1767-1784 (2016).

  • Freudenthaler, V. et al. Depolarization ratio profiling at several wavelengths in pure Saharan dust during SAMUM 2006. Tellus B 61, 165-179 (2009).

  • Freudenthaler, V. About the effects of polarising optics on lidar signals and the Delta90 calibration. Atmos. Meas. Tech., 9, 4181–4255 (2016).

History:#

  • 2018-09-02: First edition by Zhenping

  • 2018-09-04: Change the smoothing order. Smoothing the signal ratio instead of smoothing the signal.

  • 2019-05-24: Add ‘flag_smooth_before’ to control the smoothing order.

  • 2024-08-13: MH: Change calculation to GHK parameters and eta as depolarization constant.

ppcpy.retrievals.depolarization.get_MDR(vdr, vdrStd, refHInd)[source]#

get the vdr at reference height

in the matlab pollynet processing chain this is done by recalculating vdr for the reference height chunk (Pollynet_Processing_Chain/lib/calibration/pollyMDRGHK.m)

Assuming that it is more efficient to use the precalculated vdr

The snr criterion is missing for this very first version

ppcpy.retrievals.depolarization.pardepol_cldFreeGrps(data_cube, ret_prof_name)[source]#
ppcpy.retrievals.depolarization.calc_pdr(vol_depol, vol_depol_std, aer_bsc, aer_bsc_std, mol_bsc, mol_depol, mol_depol_std)[source]#

Calculate the particle depolarization ratio and estimate its standard deviation.

Parameters:#

vol_depolndarray

Volume depolarization ratio.

vol_depol_stdndarray

Standard deviation of volume depolarization ratio.

aer_bscndarray

Aerosol backscatter coefficient [m^{-1}Sr^{-1}].

aer_bsc_stdndarray

Standard deviation of aerosol backscatter coefficient [m^{-1}Sr^{-1}].

mol_bscndarray

Molecule backscatter coefficient [m^{-1}Sr^{-1}].

mol_depolfloat

Molecule depolarization ratio, dependent on central wavelength and IF bandwidth.

mol_depol_stdfloat

Standard deviation of molecule depolarization ratio.

Returns:#

par_depolndarray

Particle depolarization ratio.

par_depol_stdndarray

Standard deviation of particle depolarization ratio.

References:#

  • Freudenthaler, V., et al., Depolarization ratio profiling at several wavelengths in pure Saharan dust during SAMUM 2006, Tellus B, 61, 165-179, 2009.

History:#

  • 2021-05-31: First edition by Zhenping