m_gas_scattering.cc

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/*===========================================================================
  ===  File description
  ===========================================================================*/
 
#include "agenda_class.h"
#include "physics_funcs.h"
#include "arts_conversions.h"
#include "gas_scattering.h"
#include "optproperties.h"
#include "rte.h"
#include "transmissionmatrix.h"
#include <cmath>
 
using Constant::pi;
using Constant::boltzmann_constant;
 
 
/*===========================================================================
  === The functions
  ===========================================================================*/
 
/* Workspace method: Doxygen documentation will be auto-generated */
void gas_scatteringOff(Workspace& ws,
                       Index& gas_scattering_do,
                       Agenda& gas_scattering_agenda,
                       const Verbosity&) {
  // set flag to False (default)
  gas_scattering_do = 0;
 
  gas_scattering_agenda = Agenda(ws);
  gas_scattering_agenda.set_name("gas_scattering_agenda");
}
 
/* Workspace method: Doxygen documentation will be auto-generated */
void gas_scattering_coefXsecConst(PropagationMatrix& gas_scattering_coef,
                                 const Vector& f_grid,
                                 const Numeric& rtp_pressure,
                                 const Numeric& rtp_temperature,
                                 const Index& stokes_dim,
                                 const Numeric& ConstXsec,
                                 const Verbosity&) {
  gas_scattering_coef = PropagationMatrix(f_grid.nelem(), stokes_dim, 1, 1, ConstXsec * number_density(rtp_pressure, rtp_temperature));
}
 
/* Workspace method: Doxygen documentation will be auto-generated */
void gas_scattering_coefAirSimple(PropagationMatrix& gas_scattering_coef,
                                  const Vector& f_grid,
                                  const Numeric& rtp_pressure,
                                  const Numeric& rtp_temperature,
                                  const Index& stokes_dim,
                                  const Verbosity&) {
  static constexpr std::array coefficients{
      3.9729066, 4.6547659e-2, 4.5055995e-4, 2.3229848e-5};
 
  gas_scattering_coef = PropagationMatrix(f_grid.nelem(), stokes_dim);
 
  for (Index f = 0; f < f_grid.nelem(); f++) {
    const Numeric wavelen = Conversion::freq2wavelen(f_grid[f]) * 1e6;
    Numeric sum = 0;
    Numeric pows = 1;
    for (auto& coef: coefficients) {
      sum += coef * pows;
      pows /= Math::pow2(wavelen);
    }
    gas_scattering_coef.Kjj()[f] = 1e-32 * sum / Math::pow4(wavelen);
  }
 
  gas_scattering_coef.Kjj() *= number_density(rtp_pressure, rtp_temperature);
}
 
/* Workspace method: Doxygen documentation will be auto-generated */
void gas_scattering_matIsotropic(TransmissionMatrix& gas_scattering_mat,
                                   Vector& gas_scattering_fct_legendre,
                                   const Vector& gas_scattering_los_in,
                                   const Vector& gas_scattering_los_out,
                                   const Index& stokes_dim,
                                   const Index& gas_scattering_output_type,
                                   const Verbosity&) {
  //out
  if (gas_scattering_output_type) {
    gas_scattering_fct_legendre.resize(1);
    gas_scattering_fct_legendre = 1.;
 
  } else {
    if (gas_scattering_los_in.nelem() > 0 && gas_scattering_los_out.nelem() > 0) {
      TransmissionMatrix sca_mat_temp(1, stokes_dim);
      sca_mat_temp.setIdentity();
      gas_scattering_mat = sca_mat_temp;
    } else {
      // set the scattering matrics empty in case the in and out los are empty
      gas_scattering_mat = TransmissionMatrix();
    }
  }
}
 
/* Workspace method: Doxygen documentation will be auto-generated */
void gas_scattering_matRayleigh(TransmissionMatrix& gas_scattering_mat,
                                  Vector& gas_scattering_fct_legendre,
                                  const Vector& gas_scattering_los_in,
                                  const Vector& gas_scattering_los_out,
                                  const Index& stokes_dim,
                                  const Index& gas_scattering_output_type,
                                  const Numeric& depolarization_factor,
                                  const Verbosity&) {
 
  ARTS_USER_ERROR_IF(gas_scattering_los_in.nelem() != gas_scattering_los_out.nelem(),
    "The length of the vectors of incoming and outgoing direction must be the same.")
 
 
 
    if (gas_scattering_output_type) {
    gas_scattering_fct_legendre.resize(3);
    gas_scattering_fct_legendre = {1, 0, 0.1};
 
  } else {
 
    //if gas_scattering_los_in or gas_scattering_los_out is empty then gas_scattering_mat is empty.
    if (gas_scattering_los_in.nelem()>0 && gas_scattering_los_out.nelem()>0){
 
      Index atmosphere_dim = 1;
      if (gas_scattering_los_in.nelem()==2){
        atmosphere_dim=3;
      }
 
      //For the scattering calculation we need the propagation direction of incoming
      //and outgoing radiation. Therefore we have to convert the line of sights to
      //propagation directions.
      Vector in_prop;
      Vector out_prop;
 
      mirror_los(in_prop, gas_scattering_los_in,atmosphere_dim);
      mirror_los(out_prop, gas_scattering_los_out,atmosphere_dim);
 
      // calc_scatteringAngle() between gas_scattering_los_in and gas_scattering_los_out
      Numeric za_inc = in_prop[0];
      Numeric za_sca = out_prop[0];
 
      Numeric aa_inc = 0;
      Numeric aa_sca = 0;
      if (atmosphere_dim==3){
        aa_inc = in_prop[1];
        aa_sca = out_prop[1];
      }
 
      Numeric theta_rad = scat_angle(za_sca, aa_sca, za_inc, aa_inc);
 
      // Rayleigh phase matrix in scattering system
      Vector pha_mat_int = calc_rayleighPhaMat(theta_rad, stokes_dim);
 
      // transform the phase matrix
      Matrix pha_mat(stokes_dim, stokes_dim, 0.0);
 
      // account for depolarization factor
      Numeric delta =
          (1 - depolarization_factor) / (1 + 0.5 * depolarization_factor);
      Numeric delta_prime =
          (1 - 2 * depolarization_factor) / (1 - depolarization_factor);
      Vector depol(6, 0.0);
 
      switch (stokes_dim) {
        case 4:
          depol[5] = 1;
          pha_mat_int[5] *= delta_prime;
          [[fallthrough]];
        case 1:
          depol[0] = 1;
          depol *= 1 - delta;
          pha_mat_int += depol;
      }
 
      pha_mat_labCalc(pha_mat,
                      pha_mat_int,
                      gas_scattering_los_out[0],
                      gas_scattering_los_out[1],
                      gas_scattering_los_in[0],
                      gas_scattering_los_in[1],
                      theta_rad);
 
      TransmissionMatrix sca_mat_temp(pha_mat);
 
      gas_scattering_mat = sca_mat_temp;
    } else {
      // set the scattering matrics empty in case the in and out los are empty
      gas_scattering_mat = TransmissionMatrix();
    }
  }
}