yRadar

Replaces yCalc() for radar/lidar calculations.

The output format for iy when simulating radars and lidars differs from the standard one, and yCalc() can not be used for such simulations. This method works largely as yCalc(), but is tailored to handle the output from iyRadarSingleScat(). Note that iy_radar_agenda replaces iy_main_agenda.

The method requires additional information about the sensor, regarding its recieving properties. First of all, recieved polarisation states are taken from instrument_pol_array. Note that this WSV allows to define several measured polarisations for each transmitted signal. For example, it is possible to simulate transmittance of V and measuring backsacttered V and H.

Secondly, the range averaging is described by range_bins. These bins can either be specified in altitude or two-way travel time. In both case, the edges of the range bins shall be specified. All data (including auxiliary variables) are returned as the average inside the bins. If a bin is totally outside the model atmosphere, NaN is returned.

The options for iy_unit_radar are:

"1":
Backscatter coefficient. Unit is 1/(m*sr). At zero attenuation, this equals the scattering matrix value for the backward direction. See further AUG.
"Ze": Equivalent reflectivity. Unit is mm^6/m^3. Conversion formula is given below.
"dBZe": 10*log10(Ze/Z0), where Z0 is 1 mm^6/m^3.

The conversion from backscatter coefficient to Ze is:

Ze = 1e18 * lambda^4 / (k2 * pi^5) * sum(sigma)

where sum(sigma) = 4 * pi * b, and b is the backscatter coefficient.

The reference dielectric factor can either specified directly by the argument k2. For example, to mimic the CloudSat data, k2 shall be set to 0.75 (citaion needed). If k2 is set to be negative (which is defualt), k2 is calculated as:

k2 = abs( (n^2-1)/(n^2+2) )^2

where n is the refractive index of liquid water at temperature ze_tref and the frequency of the radar, calculated by the MPM93 parameterization.

A lower limit for dBZe is applied (dbze_min). The main reason is to handle the fact that dBZe is not defined for Ze=0, and dBZe is set to the clip value when Ze < 10^(dbze_min/10).

Author(s): Patrick Eriksson

Parameters:

y (Vector, optional) – The measurement vector. See y, defaults to self.y [OUT]
y_f (Vector, optional) – The frequencies associated with y. See y_f, defaults to self.y_f [OUT]
y_pol (ArrayOfIndex, optional) – The polarisation states associated with y. See y_pol, defaults to self.y_pol [OUT]
y_pos (Matrix, optional) – The sensor positions associated with y. See y_pos, defaults to self.y_pos [OUT]
y_los (Matrix, optional) – The line-of-sights associated with y. See y_los, defaults to self.y_los [OUT]
y_aux (ArrayOfVector, optional) – Data auxilary to y. See y_aux, defaults to self.y_aux [OUT]
y_geo (Matrix, optional) – The geo-position assigned to each element of y. See y_geo, defaults to self.y_geo [OUT]
jacobian (Matrix, optional) – The Jacobian matrix. See jacobian, defaults to self.jacobian [OUT]
atmgeom_checked (Index, optional) – OK-flag for the geometry of the model atmosphere. See atmgeom_checked, defaults to self.atmgeom_checked [IN]
atmfields_checked (Index, optional) – OK-flag for atmospheric grids and (physical) fields. See atmfields_checked, defaults to self.atmfields_checked [IN]
iy_unit_radar (String, optional) – Unit for radar simulations. See iy_unit_radar, defaults to self.iy_unit_radar [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]
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]
cloudbox_on (Index, optional) – Flag to activate the cloud box. See cloudbox_on, defaults to self.cloudbox_on [IN]
cloudbox_checked (Index, optional) – OK-flag for variables associated with the cloudbox. See cloudbox_checked, defaults to self.cloudbox_checked [IN]
sensor_pos (Matrix, optional) – The sensor position for each measurement block. See sensor_pos, defaults to self.sensor_pos [IN]
sensor_los (Matrix, optional) – The sensor line-of-sight (LOS) for each measurement block. See sensor_los, defaults to self.sensor_los [IN]
sensor_checked (Index, optional) – OK-flag for sensor related variables. See sensor_checked, defaults to self.sensor_checked [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]
iy_radar_agenda (Agenda, optional) – Calculation of pointwise backscattering. See iy_radar_agenda, defaults to self.iy_radar_agenda [IN]
instrument_pol_array (ArrayOfArrayOfIndex, optional) – Multiple definition of instrument polarisation. See instrument_pol_array, defaults to self.instrument_pol_array [IN]
range_bins (Vector, optional) – The range bins of an active instrument. See range_bins, defaults to self.range_bins [IN]
ze_tref (Numeric, optional) – Reference temperature for conversion to Ze. Defaults to 273.15 [IN]
k2 (Numeric, optional) – Reference dielectric factor. Defaults to -1 [IN]
dbze_min (Numeric, optional) – Clip value for dBZe. Defaults to -99 [IN]
verbosity (Verbosity) – ARTS verbosity. See verbosity, defaults to self.verbosity [IN]