apsfs-package: 'apsfs': Atmospheric Point Spread Function and Spherical...

In AlexCast/apsfs: Monte Carlo code for simulation of atmospheric Point Spread Functions and spatially-resolved Spherical Albedo Functions

apsfs: Atmospheric Point Spread Function and Spherical Albedo Function Simulation

Description

This package contains functions to calculate the atmopsheric point spread function (PSF) for a given geometry and atmospheric composition and profile and functions to fit this data to annular, sectorial, or grid models. It can also calculate the spatially-resolved spherical albedo function (SAF).

Details

The PSF and SAF are calculated with backward Monte Carlo with the following simplifications:

• Plane paralel geometry;

• Layered medium;

• Lambertian surface;

• Molecular absorption not included.

Simulations can be recorded in a annular for symmetric conditions (Lambertian surfaces and sensor looking at nadir), and sectorial geometry or grid geometry for asymmetric conditions (surface BRDF and or zenith view angles away from nadir).

The results can then be fitted to models to provide flexibility for application. Cumulative annular data is fitted to a two term exponential function, the sectorial data is fitted to a SVD, while grid data is fitted with Zernike polynomials.

Below is the list of exported functions in this package:

• get_mol_par: Calculate the molecular absorption and optical depth

• get_opt_atm_prfl: Calculate optical properties of atmospheric layers in high resolution

• cos2sph: Directional cosines to polar angles

• mc_psf: Solves the radiative transfer with the Monte Carlo method to simulate the PSF

• mc_saf: Solves the radiative transfer with the Monte Carlo method to simulate the SAF

• dpsf: Calculates the PSF density (per area, in m^2)

• fit_radial_psf: Fit a cumulative annular model to radial PSF geometry

• fit_grid_psf: Fit grid PSF geometry with Zernike polynomials

• calc_cdf: Calculate the cumulative density distribution from scattering phase functions

• ray_ph: Rayleigh scattering phase function

• scat_aer: Get scattering direction after aerosol interaction

• scat_ray: Get scattering direction after Rayleigh interaction

• rayleigh_od: Calculate the Rayleigh optical depth at a given pressure and altitude

• update_cdir: Update directional cosines after scattering

The following data is available:

• us62: US standard atmospheric profile (1962)

• continental_ph_6sv: Continental aerosol scattering phase function

• maritime_ph_6sv: Maritime aerosol scattering phase function

• urban_ph_6sv: Urban aerosol scattering phase function

• continental_coef_6sv: Continental aerosol optical coefficients

• maritime_coef_6sv: Maritime aerosol optical coefficients

• urban_coef_6sv: Urban aerosol optical coefficients

• tau_ray_6sv: Rayleigh optical depth for US62 and 6SV wavelength grid

• rayleigh_cdf: Cumulative distribution function of the Rayleigh scattering phase function

Author(s)

Alexandre Castagna

AlexCast/apsfs documentation built on Feb. 1, 2024, 9:48 p.m.