Forwarding Freddy's answer to the list. :-)
> Begin forwarded message: > > From: Manfred Brath <manfred.br...@uni-hamburg.de> > Subject: Re: Fwd: [arts-users] Direct radiation is subtracted when it should > not > Date: 17 October 2022 at 14:38:24 CEST > To: <mengqi....@epfl.ch> > Cc: Oliver Lemke <oliver.le...@uni-hamburg.de> > > Hello Xia, > > since the star related methods are still under development, some > documentation is still missing. Therefore, you chose unfortunately the wrong > surface agenda. The iySurfaceRtpropAgenda calculates only the surface > reflection/scattering from the diffusive radiation field. No direct radiation > is intended to be considered by this method. > > If stars are present you should use following surface methods: > > for a Lambertian surface with predefined reflectivity > > iySurfaceLambertian > iySurfaceLambertianDirect > for a flat surface with predefined reflectivity > iySurfaceFlatReflectivity > iySurfaceFlatReflectivityDirect > for a flat surface (Fresnel reflection) with defined refractive index > iySurfaceFlatRefractiveIndex > iySurfaceFlatRefractiveIndexDirect > > > Here is a example for a surface agenda with a Lambertian surface > > @arts_agenda > def iy_surface_agenda(ws): > ws.iySurfaceInit() > ws.Ignore(ws.dsurface_rmatrix_dx) > ws.Ignore(ws.dsurface_emission_dx) > ws.iySurfaceLambertian() > ws.iySurfaceLambertianDirect() > > > > and for a flat surface with Fresnel reflection > > @arts_agenda > def iy_surface_agenda(ws): > ws.iySurfaceInit() > ws.iySurfaceFlatRefractiveIndex() > ws.iySurfaceFlatRefractiveIndexDirect() > > > > I hope this could help you. > > Cheers, > > Freddy > > Am 17.10.22 um 13:06 schrieb Lemke, Oliver: >> >> >>> Begin forwarded message: >>> >>> From: Xia Mengqi <mengqi....@epfl.ch <mailto:mengqi....@epfl.ch>> >>> Subject: [arts-users] Direct radiation is subtracted when it should not >>> Date: 16 October 2022 at 14:05:16 CEST >>> To: "arts_users.mi@lists.uni-hamburg.de >>> <mailto:arts_users.mi@lists.uni-hamburg.de>" >>> <arts_users.mi@lists.uni-hamburg.de >>> <mailto:arts_users.mi@lists.uni-hamburg.de>> >>> >>> Hi, >>> >>> I'm new to ARTS and I set up a simple 1D test where there is sun, >>> absorption only gas and a specular surface with reflectivity 1. The sun and >>> sensor is both at 0 latitude and 0 longitude, with the sensor looking down >>> (los=180). For simplicity I force it to be just 1 layer by providing the >>> pressures on the top of the atmosphere and at 0km. I noticed that the >>> radiance output is almost zero, which is unexpected. However, if I comment >>> out the operation that subtracts the direct radiation (iy-=iy_aux[0]) in >>> iySurfaceRtpropAgenda the result looks correct (and validated against >>> libRadtran). I'm puzzled why in this case the subtraction is needed; or >>> maybe I made simple mistakes in the set up. It would be great if you could >>> help me with this problem. Thank you! >>> >>> >>> The main part of the code is copied here: >>> >>> ws = Workspace(verbosity=2) >>> ws.ReadHITRAN(filename='/home/mandy/Github/MiAtmosphere/HITRAN/ALL.par', >>> hitran_type="Online", abs_lines=ws.abs_lines) >>> >>> ws.LegacyContinuaInit() >>> ws.water_p_eq_agendaSet() >>> ws.gas_scattering_agendaSet() >>> ws.PlanetSet(option="Earth") >>> ws.iy_main_agendaSet( option="Clearsky" ) >>> ws.iy_space_agendaSet( option="CosmicBackground" ) >>> ws.iy_surface_agendaSet() >>> >>> ws.ArrayOfStringSet( ws.iy_aux_vars, [ "Optical depth", "Radiative >>> background"] ) >>> >>> ws.propmat_clearsky_agenda=propmat_clearsky_agenda >>> >>> ws.NumericSet( ws.ppath_lmax, 1e10) >>> ws.ppath_step_agendaSet( option="GeometricPath" ) >>> ws.ppath_agendaSet( option="FollowSensorLosPath" ) >>> >>> # define environment >>> # >>> ============================================================================= >>> # Number of Stokes components to be computed >>> ws.IndexSet(ws.stokes_dim, 1) >>> >>> # Read the spectroscopic line data from the ARTS catalogue and >>> # create the workspace variable `lines'. >>> ws.ReadHITRAN(filename='/home/mandy/Github/MiAtmosphere/HITRAN/ALL.par', >>> hitran_type="Online", abs_lines=ws.abs_lines) >>> ws.abs_linesNormalization(ws.abs_lines, "VVH") >>> >>> # Frequency grid >>> c = 299792458 >>> wavelengths = np.linspace(1178e-9, 1177e-9, 2) >>> f_grid = c / wavelengths >>> ws.f_grid = f_grid >>> >>> #### >>> # set a simple blackbody sun >>> ws.starsAddSingleBlackbody(latitude=sun_pos[0], longitude=sun_pos[1]) >>> ws.Print(ws.stars, 2) >>> >>> # A pressure grid rougly matching 0 to 80 km, in steps of 2 km. >>> #ws.p_grid = data.p.to_numpy() >>> ws.p_grid = np.array([1.01040e+05, 2.54000e-03]) # 0 and 120km >>> >>> # Definition of species >>> ws.abs_speciesSet(species= >>> ["H2O", "O3", "N2O", "CO", "CH4", "CO2", "O2"]) >>> >>> # This separates the lines into the different tag groups and creates >>> # the workspace variable `abs_lines_per_species': >>> ws.abs_lines_per_speciesCreateFromLines() >>> >>> # Load atmospheric data >>> ws.AtmRawRead(basename="../controlfiles/testdata/afglUS") >>> >>> # Set surface relectivity >>> Reflectivity = [1] >>> ws.VectorSet(ws.surface_scalar_reflectivity, Reflectivity) >>> ws.surface_rtprop_agendaSet(option="Specular_NoPol_ReflFix_SurfTFromt_surface" >>> ) >>> >>> # Reference ellipsoid >>> ws.refellipsoidEarth(ws.refellipsoid, "Sphere") >>> >>> # No jacobian calculations >>> ws.jacobianOff() >>> >>> # No particulate scattering >>> ws.cloudboxOff() >>> >>> # No sensor model >>> ws.sensorOff() >>> >>> ws.StringSet( ws.iy_unit, "1" ) >>> >>> ws.AtmosphereSet1D() >>> ws.AtmFieldsCalc() >>> >>> # Postion and line-of-sight of sensor >>> ws.rte_pos = [600e3] >>> ws.rte_los = [180] >>> ws.VectorSet(ws.rte_pos2, []) >>> >>> # Check model atmosphere >>> ws.propmat_clearsky_agendaAuto() >>> ws.propmat_clearsky_agenda_checkedCalc() >>> ws.atmfields_checkedCalc() >>> ws.atmgeom_checkedCalc() >>> ws.cloudbox_checkedCalc() >>> ws.lbl_checkedCalc() >>> >>> # the actual simulation >>> ws.iyCalc() >>> >>> # output iy file >>> ws.WriteXML(ws.output_file_format, ws.iy) >> > -- > ---------------------------------------------------------- > Dr. Manfred Brath > Radiation and Remote Sensing > Meteorological Institute > Universität Hamburg > Bundesstraße 55 > D-20146 Hamburg > Room 1535 > > Tel: +49 40 42838-8786
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