# ARTS built-in documentation server

## Workspace Method iyEmissionHybrid

### Description

Radiative transfer with emission and precalculated radiation field. This method works largely as iyEmissionStandard but incorporates scattering by a precalculated radiation field. It is so far limited to 1D calculations. The method integrates the source term along the propagation path. While iyEmissionStandard only considers local thermal emission, this method also includes scattering into the line-of-sight in the source term. The scattering integral is solved with the precalculated field as incoming radiation. That is, this method extends the integration into the cloudbox, while iyEmissionStandard starts at the cloudbox boundary. The calculate radiance should be as exact as what is produced by the scattering solver used to calculate the precalculted radiation field, but the main reason to use this method is to obtain the Jacobian even in the presence of scattering. The Jacobian with respect to bulk scattering properties can be obtained, but it is approximate. This is the case as the incoming radiation field is treated as fixed in the calculation of the Jacobian. The impact of this approximation increases with the degree of scattering.

**Authors: **Patrick Eriksson, Jana Mendrok, Richard Larsson

### Synopsis

### Variables

OUT | iy | (Matrix) | Monochromatic pencil beam radiance spectrum. |

OUT | iy_aux | (ArrayOfMatrix) | Data auxiliary to iy. |

OUT+IN | diy_dx | (ArrayOfTensor3) | Derivative of iy with respect to retrieval quantities. |

OUT | ppvar_p | (Vector) | Pressure along the propagation path. |

OUT | ppvar_t | (Vector) | Temperature along the propagation path. |

OUT | ppvar_nlte | (EnergyLevelMap) | Non-LTE temperatures/ratios along the propagation path. |

OUT | ppvar_vmr | (Matrix) | VMR values along the propagation path. |

OUT | ppvar_wind | (Matrix) | Winds along the propagation path. |

OUT | ppvar_mag | (Matrix) | Magnetic field along the propagation path. |

OUT | ppvar_pnd | (Matrix) | PND values along the propagation path. |

OUT | ppvar_f | (Matrix) | Doppler adjusted frequencies along the propagation path. |

OUT | ppvar_iy | (Tensor3) | iy-values along the propagation path. |

OUT | ppvar_trans_cumulat | (Tensor4) | The transmittance between the sensor and each point of the propagation path. |

OUT | ppvar_trans_partial | (Tensor4) | The transmittance between the points along the propagation path. |

IN | iy_id | (Index) | Identification number of iy. |

IN | stokes_dim | (Index) | The dimensionality of the Stokes vector (1-4). |

IN | f_grid | (Vector) | The frequency grid for monochromatic pencil beam calculations. |

IN | atmosphere_dim | (Index) | The atmospheric dimensionality (1-3). |

IN | p_grid | (Vector) | The pressure grid. |

IN | t_field | (Tensor3) | The field of atmospheric temperatures. |

IN | nlte_field | (EnergyLevelMap) | The field of NLTE temperatures and/or ratios. |

IN | vmr_field | (Tensor4) | VMR field. |

IN | abs_species | (ArrayOfArrayOfSpeciesTag) | Tag groups for gas absorption. |

IN | wind_u_field | (Tensor3) | Zonal component of the wind field. |

IN | wind_v_field | (Tensor3) | Meridional component of the magnetic field. |

IN | wind_w_field | (Tensor3) | Vertical wind component field. |

IN | mag_u_field | (Tensor3) | Zonal component of the magnetic field. |

IN | mag_v_field | (Tensor3) | Meridional component of the magnetic field. |

IN | mag_w_field | (Tensor3) | Vertical component of the magnetic field. |

IN | cloudbox_on | (Index) | Flag to activate the cloud box. |

IN | cloudbox_limits | (ArrayOfIndex) | The limits of the cloud box. |

IN | pnd_field | (Tensor4) | Particle number density field. |

IN | dpnd_field_dx | (ArrayOfTensor4) | Partial derivatives of pnd_field. |

IN | scat_species | (ArrayOfString) | Array of Strings defining the scattering species to consider. |

IN | scat_data | (ArrayOfArrayOfSingleScatteringData) | Array of single scattering data. |

IN | iy_unit | (String) | Selection of output unit for radiative transfer methods. |

IN | iy_aux_vars | (ArrayOfString) | Selection of quantities for iy_aux and when applicable also y_aux. |

IN | jacobian_do | (Index) | Flag to activate (clear-sky) Jacobian calculations. |

IN | jacobian_quantities | (ArrayOfRetrievalQuantity) | The retrieval quantities in the Jacobian matrix. |

IN | propmat_clearsky_agenda | (Agenda) | Agenda calculating the absorption coefficient matrices. |

IN | water_p_eq_agenda | (Agenda) | Agenda to calculate the saturation pressure of water. |

IN | rt_integration_option | (String) | Switch between integration approaches for radiative transfer steps. |

IN | iy_main_agenda | (Agenda) | Agenda calculating the single monochromatic pencil beam spectrum. |

IN | iy_space_agenda | (Agenda) | Agenda providing the downwelling radiation at the top of the atmosphere. |

IN | iy_surface_agenda | (Agenda) | Agenda providing the upwelling radiation from the surface. |

IN | iy_cloudbox_agenda | (Agenda) | Agenda deriving the intensity at boundary or interior of the cloudbox. |

IN | iy_agenda_call1 | (Index) | Flag to handle recursive calls of iy_main_agenda The agenda iy_main_agenda can be used recursively and this flag is used to tell the methods inside the agenda which is the primary call. |

IN | iy_transmittance | (Tensor3) | Transmittance to be included in iy. |

IN | ppath | (Ppath) | The propagation path for one line-of-sight. |

IN | rte_pos2 | (Vector) | A second geographical position to define the geometry for radiative transfer calculations. |

IN | rte_alonglos_v | (Numeric) | Velocity along the line-of-sight to consider for a RT calculation. |

IN | surface_props_data | (Tensor3) | Various surface properties. |

IN | cloudbox_field | (Tensor7) | The spectral radiance field inside the cloudbx. |

IN | za_grid | (Vector) | Zenith angle grid. |

GIN | Naa_grid | (Index, Default: 19) | Number of azimuth angles to consider in scattering source term integral. |

GIN | t_interp_order | (Index, Default: 1) | Interpolation order of temperature for scattering data (so far only applied in phase matrix, not in extinction and absorption. |