ppcpy.retrievals.raman#

Functions

calc_raman_bsc

Calculate the aerosol backscatter coefficient with the Raman method.

lidarratio

Calculate aerosol lidar ratio.

raman_bsc

Calculate uncertainty of aerosol backscatter coefficient with Monte-Carlo simulation.

raman_ext

Retrieve the aerosol extinction coefficient with the Raman method.

run_cldFreeGrps

smoothWin

Smooth signal with a height-dependent window.
ppcpy.retrievals.raman.run_cldFreeGrps(data_cube, signal='TCor', heightFullOverlap=None, nr=False, collect_debug=True)[source]#
ppcpy.retrievals.raman.raman_ext(height, sig, lambda_emit, lambda_Raman, alpha_molecular_elastic, alpha_molecular_Raman, number_density, angstrom, window_size, method='movingslope', MC_count=1, bg=0)[source]#

Retrieve the aerosol extinction coefficient with the Raman method.

Parameters:

  • height (array_like) – Height [m].

  • sig (array_like) – Measured Raman signal. Unit: Photon Count.

  • lambda_emit (float) – Wavelength of the emitted laser beam [nm].

  • lambda_Raman (float) – Wavelength of Raman signal [nm].

  • alpha_molecular_elastic (array_like) – Molecular scattering coefficient at emitted wavelength in m^-1 sr^-1.

  • alpha_molecular_Raman (array_like) – Molecular scattering coefficient at Raman wavelength in m^-1 sr^-1.

  • number_density (array_like) – Molecular number density.

  • angstrom (float) – Angstrom exponent for aerosol extinction coefficient.

  • window_size (int) – Window size for smoothing the signal using Savitzky-Golay filter.

  • method (str, optional) – Method to calculate the slope of the signal. Choices: ‘movingslope’, ‘smoothing’, ‘chi2’. Default is ‘movingslope’.

  • MC_count (int, optional) – Number of Monte Carlo iterations. Default is 1.

  • bg (float, optional) – Background signal (Photon Count). Default is 0.

Returns:

  • ext_aer (ndarray) – Aerosol extinction coefficient [m^-1].

  • ext_error (ndarray) – Error in aerosol extinction coefficient [m^-1] (only calculated for MC_count > 1).

References

Ansmann, A. et al. Independent measurement of extinction and backscatter profiles in cirrus clouds by using a combined Raman elastic-backscatter lidar. Applied Optics Vol. 31, Issue 33, pp. 7113-7131 (1992).

History#

  • 2021-05-31: First edition by Zhenping

  • 2025-01-05: AI supported translation

ppcpy.retrievals.raman.raman_bsc(height, sigElastic, sigVRN2, ext_aer, angstroem, ext_mol, beta_mol, ext_mol_raman, beta_mol_inela, HRef, betaRef, window_size=40, flagSmoothBefore=True, el_lambda=None, inel_lambda=None, bgElastic=None, bgVRN2=None, sigma_ext_aer=None, sigma_angstroem=None, MC_count=3, method='monte-carlo', collect_debug=False)[source]#

Calculate uncertainty of aerosol backscatter coefficient with Monte-Carlo simulation.

Parameters:

  • height (np.ndarray) – Heights in meters.

  • sigElastic (np.ndarray) – Elastic photon count signal.

  • sigVRN2 (np.ndarray) – N2 vibration rotational Raman photon count signal.

  • ext_aer (np.ndarray) – Aerosol extinction coefficient (m^{-1}).

  • angstroem (np.ndarray) – Aerosol Angstrom exponent.

  • ext_mol (np.ndarray) – Molecular extinction coefficient (m^{-1}).

  • beta_mol (np.ndarray) – Molecular backscatter coefficient (m^{-1}Sr^{-1}).

  • ext_mol_raman (np.ndarray) – Molecular extinction coefficient for Raman wavelength.

  • beta_mol_inela (np.ndarray) – Molecular backscatter coefficient for inelastic wavelength.

  • HRef (list or tuple) – Reference region [m].

  • betaRef (float) – Aerosol backscatter coefficient at the reference region.

  • window_size (int) – Number of bins for the sliding window for signal smoothing. Default is 40.

  • flagSmoothBefore (bool) – Flag to control the smoothing order. Default is True.

  • el_lambda (int) – Elastic wavelength in nm.

  • inel_lambda (int) – Inelastic wavelength in nm.

  • bgElastic (np.ndarray) – Background of elastic signal.

  • bgVRN2 (np.ndarray) – Background of N2 vibration rotational signal.

  • sigma_ext_aer (np.ndarray) – Uncertainty of aerosol extinction coefficient (m^{-1}).

  • sigma_angstroem (np.ndarray) – Uncertainty of Angstrom exponent.

  • MC_count (int or list) – Samples for each error source. Default is 3.

  • method (str) – Computational method (‘monte-carlo’ or ‘analytical’). Default is ‘monte-carlo’.

Returns:

Aerosol backscatter coefficient (m^{-1}Sr^{-1}). aerBscStd (np.ndarray): Uncertainty of aerosol backscatter coefficient (m^{-1}Sr^{-1}). LR (np.ndarray): Aerosol Lidar ratio.

Return type:

beta_aer (np.ndarray)

ppcpy.retrievals.raman.calc_raman_bsc(height, sigElastic, sigVRN2, ext_aer, angstroem, ext_mol, beta_mol, ext_mol_raman, beta_mol_inela, HRef, wavelength, betaRef, window_size=40, flagSmoothBefore=True, el_lambda=None, inel_lambda=None)[source]#

Calculate the aerosol backscatter coefficient with the Raman method.

Parameters:

  • height (array) – Height in meters.

  • sigElastic (array) – Elastic photon count signal.

  • sigVRN2 (array) – N2 vibration rotational Raman photon count signal.

  • ext_aer (array) – Aerosol extinction coefficient in m^{-1}.

  • angstroem (array) – Aerosol Angstrom exponent.

  • ext_mol (array) – Molecular extinction coefficient in m^{-1}.

  • beta_mol (array) – Molecular backscatter coefficient in m^{-1}Sr^{-1}.

  • ext_mol_raman (array) – Molecular extinction coefficient for Raman wavelength in m^{-1}.

  • beta_mol_inela (array) – Molecular inelastic backscatter coefficient in m^{-1}Sr^{-1}.

  • HRef (list) – Reference region in meters [start, end].

  • wavelength (int) – Wavelength of the elastic signal in nm.

  • betaRef (float) – Aerosol backscatter coefficient at the reference region in m^{-1}Sr^{-1}.

  • window_size (int, optional) – Number of bins for the sliding window for signal smoothing. Default is 40.

  • flagSmoothBefore (bool, optional) – Whether to smooth the signal before or after calculating the signal ratio. Default is True.

  • el_lambda (int, optional) – Elastic wavelength in nm.

  • inel_lambda (int, optional) – Inelastic wavelength in nm.

Returns:

  • beta_aer (array) – Aerosol backscatter coefficient in m^{-1}Sr^{-1}.

  • LR (array) – Aerosol lidar ratio.

References

Ansmann, A., et al. (1992). “Independent measurement of extinction and backscatter profiles in cirrus clouds by using a combined Raman elastic-backscatter lidar.” Applied optics 31(33): 7113-7131.

History#

  • 2018-01-02: First edition by Zhenping.

  • 2018-07-24: Added ext_mol_factor and ext_aer_factor for wavelength of 1064nm.

  • 2018-09-04: Changed smoothing order for signal ridge stability.

  • 2024-11-12: Modified by HB for consistency in 2024.

ppcpy.retrievals.raman.smoothWin(signal, win, method='moving')[source]#

Smooth signal with a height-dependent window.

Parameters:

  • signal (array) – Input signal array.

  • win (int or array) – Window size. Can be a fixed scalar or a variable-length array.

  • method (str, optional) – Smoothing method. Default is ‘moving’.

Returns:

signalSM – Smoothed signal.

Return type:

array

ppcpy.retrievals.raman.lidarratio(aerExt, aerBsc, hRes=7.5, aerExtStd=None, aerBscStd=None, smoothWinExt=1, smoothWinBsc=1)[source]#

Calculate aerosol lidar ratio.

Parameters:

  • aerExt (ndarray) – Aerosol extinction coefficient. (m^-1)

  • aerBsc (ndarray) – Aerosol backscatter coefficient. (m^-1sr^-1)

  • hRes (float, optional) – Vertical resolution of each height bin. (m). Default is 7.5.

  • aerExtStd (ndarray, optional) – Uncertainty of aerosol extinction coefficient. (m^-1)

  • aerBscStd (ndarray, optional) – Uncertainty of aerosol backscatter coefficient. (m^-1sr^-1)

  • smoothWinExt (int, optional) – Applied smooth window length for calculating aerosol extinction coefficient. Default is 1.

  • smoothWinBsc (int, optional) – Applied smooth window length for calculating aerosol backscatter coefficient. Default is 1.

Returns:

  • aerLR (ndarray) – Aerosol lidar ratio. (sr)

  • effRes (float) – Effective resolution of lidar ratio. (m)

  • aerLRStd (ndarray) – Uncertainty of aerosol lidar ratio. (sr)

References

Mattis, I., D’Amico, G., Baars, H., Amodeo, A., Madonna, F., and Iarlori, M.: EARLINET Single Calculus Chain–technical–Part 2: Calculation of optical products, Atmospheric Measurement Techniques, 9, 3009-3029, 2016.

History#

2021-07-20: First edition by Zhenping (translated to Python)