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Workspace Method iyCloudRadar

Description

Simulation of cloud radars, restricted to single scattering.

The WSM treats radar measurements of cloud and precipitation, on
the condition that multiple scattering can be ignored. Beside the
direct backsacttering, the two-way attenuation by gases and
particles is considered. Surface scattering is ignored. Further
details are given in AUG.

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

The method can be used with iyCalc, but not with yCalc. In the
later case, use instead yCloudRadar.

The method returns the backscattering 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_agenda, see further *iy_transmitterCloudRadar*
If the radar transmits several polarisations at the same frequency,
you need to handle this by using two frequencies in f_grid, but
but these can be almost identical.

The options iy_unit are:
 "1"  : Backscatter coefficient. Unit is 1/(m*sr). Without
          attenuation, this equals the scattering matrix value for
          the backward direction. See further AUG.
 "Ze" : Equivalent reflectivity. I the conversion, "K" is
          calculated using the refractive index for liquid water,
          at the temperature defined by *ze_tref*.

No Jacobian quantities are yet handled.

The following auxiliary data can be obtained:
  "Pressure": The pressure along the propagation path.
     Size: [1,1,1,np].
  "Temperature": The temperature along the propagation path.
     Size: [1,1,1,np].
  "Backscattering": The un-attenuated backscattering. Unit
     follows iy_unit. Size: [nf,ns,1,np].
  "Transmission": The single-way transmission matrix from the
     transmitter to each propagation path point. The matrix is
     valid for the photon direction. Size: [nf,ns,ns,np].
  "Round-trip time": The time for the pulse to propagate. For a 
     totally correct result, refraction must be considered (in
     *pppath_agenda*). Size: [1,1,1,np].
  "PND, type X": The particle number density for particle type X
       (ie. corresponds to book X in pnd_field). Size: [1,1,1,np].
  "Mass content, X": The particle content for mass category X.
       This corresponds to column X in particle_masses (zero-
       based indexing). Size: [1,1,1,np].

Authors: Patrick Eriksson

Synopsis

iyCloudRadar(

iy, iy_aux, ppath, stokes_dim, f_grid, atmosphere_dim, p_grid, z_field, t_field, vmr_field, wind_u_field, wind_v_field, wind_w_field, mag_u_field, mag_v_field, mag_w_field, cloudbox_on, cloudbox_limits, pnd_field, use_mean_scat_data, scat_data_array, particle_masses, iy_unit, iy_aux_vars, jacobian_do, ppath_agenda, propmat_clearsky_agenda, iy_transmitter_agenda, iy_agenda_call1, iy_transmission, rte_pos, rte_los, rte_alonglos_v, ppath_lraytrace, ze_tref )

Variables

OUT	iy	(Matrix)	Monochromatic pencil beam radiance spectrum.
OUT	iy_aux	(ArrayOfTensor4)	Data auxiliary to iy.
OUT	ppath	(Ppath)	The propagation path for one line-of-sight.
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	z_field	(Tensor3)	The field of geometrical altitudes.
IN	t_field	(Tensor3)	The field of atmospheric temperatures.
IN	vmr_field	(Tensor4)	VMR field.
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	use_mean_scat_data	(Index)	Flag to use same scattering properties for all frequencies.
IN	scat_data_array	(ArrayOfSingleScatteringData)	Raw data of single scattering data.
IN	particle_masses	(Matrix)	The mass of individual particles (or bulks).
IN	iy_unit	(String)	Selection of output unit for some 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 jacobian calculations.
IN	ppath_agenda	(Agenda)	See agendas.cc.
IN	propmat_clearsky_agenda	(Agenda)	See agendas.cc.
IN	iy_transmitter_agenda	(Agenda)	See agendas.cc.
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_transmission	(Tensor3)	Transmission to be included in iy.
IN	rte_pos	(Vector)	A geographical position for starting radiative transfer calculations.
IN	rte_los	(Vector)	A line-of-sight for (complete) radiative transfer calculations.
IN	rte_alonglos_v	(Numeric)	Velocity along the line-of-sight to consider for a RT calculation.
IN	ppath_lraytrace	(Numeric)	Maximum length of ray tracing steps when determining propagation paths.
GIN	ze_tref	(Numeric, Default: 273.15)	Reference temperature for conversion to Ze