iyRadarSingleScat

Simulation of radar, restricted to single scattering.

The WSM treats e.g. radar measurements of cloud and precipitation, on the condition that multiple scattering can be ignored. Beside the direct back-scattering, the two-way attenuation by gases and particles is considered. Surface scattering/clutter is ignored.

The method could potentially be used for lidars, but multiple scattering poses here a must stronger constrain for the range of applications.

The method shall be used with yRadar(), NOT with yCalc().

The ppath provided should be calculated including cloudbox interior:

ppathCalc( cloudbox_on=0 )

The method returns the back-scattering for each point of ppath. Several frequencies can be treated in parallel. The size of iy is [ nf * np, stokes_dim ], where nf is the length of f_grid and np is the number of path points. The data are stored in blocks of [ np, stokes_dim ]. That is, all the results for the first frequency occupy the np first rows of iy etc.

The polarisation state of the transmitted pulse is taken from iy_transmitter. If the radar transmits several polarisations at the same frequency, you need to handle this by using two frequencies in f_grid, but these can be almost identical.

This method does not consider iy_unit_radar. Unit changes are instead applied in yRadar(). The output of this method matches the option “1”.

The extinction due to particles can be scaled (by pext_scaling), which could be of interest when e.g. characterising inversions or trying to compensate for ignored multiple scattering. The later is commented further for particle_bulkpropRadarOnionPeeling().

For Jacobian calculations the default is to assume that the transmittance is unaffected by the retrieval quantities. This is done to save computational time, and should be a valid approximation for the single-scattering conditions. Set trans_in_jacobian to 1 to activate full Jacobian calculations.

Some auxiliary radiative transfer quantities can be obtained. Auxiliary quantities are selected by iy_aux_vars and returned by iy_aux. Valid choices for auxiliary data are:

"Radiative background":
Index value flagging the radiative background. The following coding is used: 0=space, 1=surface and 2=cloudbox (the last case should not occur!). Only column matching first Stokes element filled. Other columns are set to 0.
"Backscattering":
The unattenuated back-scattering. That is, as iy but with no attenuated applied. Here all columns are filled. By combing iy and this auxiliary variable, the total two-way attenuation can be derived.
"Abs species extinction":
Extinction due to abs_species at each ppath point, taken as the diagonal of the local extinction matrix.
"Particle extinction":
Extinction due to particles at each ppath point, taken as the diagonal of the local extinction matrix. The retunred values includes pext_scaling

Author(s): Patrick Eriksson

Parameters:

iy (Matrix, optional) – Monochromatic pencil beam radiance spectrum. See iy, defaults to self.iy [OUT]
iy_aux (ArrayOfMatrix, optional) – Data auxiliary to iy. See iy_aux, defaults to self.iy_aux [OUT]
diy_dx (ArrayOfTensor3, optional) – Derivative of iy with respect to retrieval quantities. See diy_dx, defaults to self.diy_dx [OUT]
ppvar_p (Vector, optional) – Pressure along the propagation path. See ppvar_p, defaults to self.ppvar_p [OUT]
ppvar_t (Vector, optional) – Temperature along the propagation path. See ppvar_t, defaults to self.ppvar_t [OUT]
ppvar_vmr (Matrix, optional) – VMR values along the propagation path. See ppvar_vmr, defaults to self.ppvar_vmr [OUT]
ppvar_wind (Matrix, optional) – Winds along the propagation path. See ppvar_wind, defaults to self.ppvar_wind [OUT]
ppvar_mag (Matrix, optional) – Magnetic field along the propagation path. See ppvar_mag, defaults to self.ppvar_mag [OUT]
ppvar_pnd (Matrix, optional) – PND values along the propagation path. See ppvar_pnd, defaults to self.ppvar_pnd [OUT]
ppvar_f (Matrix, optional) – Doppler adjusted frequencies along the propagation path. See ppvar_f, defaults to self.ppvar_f [OUT]
stokes_dim (Index, optional) – The dimensionality of the Stokes vector (1-4). See stokes_dim, defaults to self.stokes_dim [IN]
f_grid (Vector, optional) – The frequency grid for monochromatic pencil beam calculations. See f_grid, defaults to self.f_grid [IN]
atmosphere_dim (Index, optional) – The atmospheric dimensionality (1-3). See atmosphere_dim, defaults to self.atmosphere_dim [IN]
p_grid (Vector, optional) – The pressure grid. See p_grid, defaults to self.p_grid [IN]
t_field (Tensor3, optional) – The field of atmospheric temperatures. See t_field, defaults to self.t_field [IN]
nlte_field (EnergyLevelMap, optional) – The field of NLTE temperatures and/or ratios. See nlte_field, defaults to self.nlte_field [IN]
vmr_field (Tensor4, optional) – VMR field. See vmr_field, defaults to self.vmr_field [IN]
abs_species (ArrayOfArrayOfSpeciesTag, optional) – Tag groups for gas absorption. See abs_species, defaults to self.abs_species [IN]
wind_u_field (Tensor3, optional) – Zonal component of the wind field. See wind_u_field, defaults to self.wind_u_field [IN]
wind_v_field (Tensor3, optional) – Meridional component of the magnetic field. See wind_v_field, defaults to self.wind_v_field [IN]
wind_w_field (Tensor3, optional) – Vertical wind component field. See wind_w_field, defaults to self.wind_w_field [IN]
mag_u_field (Tensor3, optional) – Zonal component of the magnetic field. See mag_u_field, defaults to self.mag_u_field [IN]
mag_v_field (Tensor3, optional) – Meridional component of the magnetic field. See mag_v_field, defaults to self.mag_v_field [IN]
mag_w_field (Tensor3, optional) – Vertical component of the magnetic field. See mag_w_field, defaults to self.mag_w_field [IN]
cloudbox_on (Index, optional) – Flag to activate the cloud box. See cloudbox_on, defaults to self.cloudbox_on [IN]
cloudbox_limits (ArrayOfIndex, optional) – The limits of the cloud box. See cloudbox_limits, defaults to self.cloudbox_limits [IN]
pnd_field (Tensor4, optional) – Particle number density field. See pnd_field, defaults to self.pnd_field [IN]
dpnd_field_dx (ArrayOfTensor4, optional) – Partial derivatives of pnd_field. See dpnd_field_dx, defaults to self.dpnd_field_dx [IN]
scat_species (ArrayOfString, optional) – Array of Strings defining the scattering species to consider. See scat_species, defaults to self.scat_species [IN]
scat_data (ArrayOfArrayOfSingleScatteringData, optional) – Array of single scattering data. See scat_data, defaults to self.scat_data [IN]
scat_data_checked (Index, optional) – OK-flag for scat_data. See scat_data_checked, defaults to self.scat_data_checked [IN]
iy_aux_vars (ArrayOfString, optional) – Selection of quantities for iy_aux and when applicable also y_aux. See iy_aux_vars, defaults to self.iy_aux_vars [IN]
jacobian_do (Index, optional) – Flag to activate (clear-sky) Jacobian calculations. See jacobian_do, defaults to self.jacobian_do [IN]
jacobian_quantities (ArrayOfRetrievalQuantity, optional) – The retrieval quantities in the Jacobian matrix. See jacobian_quantities, defaults to self.jacobian_quantities [IN]
ppath (Ppath, optional) – The propagation path for one line-of-sight. See ppath, defaults to self.ppath [IN]
iy_transmitter (Matrix, optional) – Monochromatic pencil beam radiance spectrum of transmitter signal. See iy_transmitter, defaults to self.iy_transmitter [IN]
propmat_clearsky_agenda (Agenda, optional) – Calculate the absorption coefficient matrix. See propmat_clearsky_agenda, defaults to self.propmat_clearsky_agenda [IN]
water_p_eq_agenda (Agenda, optional) – Calculation of the saturation pressure of water. See water_p_eq_agenda, defaults to self.water_p_eq_agenda [IN]
rte_alonglos_v (Numeric, optional) – Velocity along the line-of-sight to consider for a RT calculation. See rte_alonglos_v, defaults to self.rte_alonglos_v [IN]
trans_in_jacobian (Index, optional) – Flag determining if change in transmittance is considered in calculation of the Jacobian or not. Defaults to 0 [IN]
pext_scaling (Numeric, optional) – Particle extinction is scaled with this value. A value inside [0,2]. Set it to 0 if you want to remove particle extinction totally. Defaults to 1 [IN]
t_interp_order (Index, optional) – Interpolation order of temperature for scattering data (so far only applied in phase matrix, not in extinction and absorption. Defaults to 1 [IN]
verbosity (Verbosity) – ARTS verbosity. See verbosity, defaults to self.verbosity [IN]