Hi Freddy,
Thanks for getting back to me. My question is about the result of using a
specular reflective surface versus using a Lambertian surface. I was thinking
the ratio should be pi (the specular one is larger) because when there is no
scattering the only difference is the BRDF evaluation. However, I observed the
Lambertian result is much smaller, more than 1e4 times smaller than the
specular result. I tried "Test_iySurfaceLambertian.py" and it is also the case
there when I change the Lambertian surface to specular.
Thanks,
Mengqi
________________________________
From: Manfred Brath <manfred.br...@uni-hamburg.de>
Sent: Wednesday, October 19, 2022 5:19:20 PM
To: Xia Mengqi; arts_users.mi@lists.uni-hamburg.de
Subject: Re: Fwd: [arts-users] Direct radiation is subtracted when it should not
Hi Mengqi,
I do not understand your problem from the information of your email, but maybe
you can have a look in "Test_iySurfaceLambertian.py", which you can find in
your arts-folder:
controlfiles-python/artscomponents/surface/
Another thing, how do you calculate your pi-ratio? When I use the above
mentioned test script and set the sun at 0 lat and 0 lon and divide the top of
the atmosphere (TOA) solar radiation F by pi I got the same value as from yCalc.
F=ws.stars.value[0].spectrum.value*scale_factor
scale_factor=sun_radius**2/(sun_radius**2+sun2TOA_distance**2)
The scale factor is needed, because the star irradiance spectrum in ARTS is
defined at the surface of the sun and not at TOA.
Cheers,
Freddy
Am 18.10.22 um 12:56 schrieb Xia Mengqi:
Thank you Freddy! This makes sense.
I tried with flat reflective surface and lambertian surface with absorption
only. I extended the 1D atmosphere to 3D so I can provide surface temperature
(set it to a really small value) but in theory since there is no scattering the
path that contributes is unchanged. I found that the flat reflective surface
result is correct but the lambertian one is much smaller than the expected pi
ratio. I tried to print ppath and I found los changing quite a lot. I am
wondering if this is the expected behavior and maybe there is something about
the 3D setup I did not understand properly. I copied the main part of the code
below.
Thanks!
Mengqi
@arts_agenda
def propmat_clearsky_agenda(ws):
ws.Ignore(ws.rtp_mag)
ws.Ignore(ws.rtp_los)
ws.propmat_clearskyInit()
ws.propmat_clearskyAddConts()
ws.propmat_clearskyAddLines()
@arts_agenda
def gas_scattering_agenda(ws):
ws.Ignore(ws.rtp_vmr)
ws.gas_scattering_coefXsecConst(ConstXsec=4.65e-31)
ws.gas_scattering_matIsotropic()
# surface scattering agenda
# lambertian
@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()
# flat reflective surface
# @arts_agenda
# def iy_surface_agenda(ws):
# ws.iySurfaceInit()
# ws.iySurfaceFlatReflectivity()
# ws.iySurfaceFlatReflectivityDirect()
# generate atmosphere data
dataset_path = '/home/mandy/Github/arts/build_new/afgl_1986-us_standard.nc'
save_path = '/home/mandy/Github/arts/controlfiles/testdata/'
data = generate_atmos_arts(dataset_path, save_path)
# =============================================================================
# open workspace
# =============================================================================
ws = Workspace()
ws.verbositySetScreen(level=2)
# =============================================================================
# generate atmosphere data
# =============================================================================
dataset_path = '/home/mandy/Github/arts/build_new/afgl_1986-us_standard.nc'
save_path = '/home/mandy/Github/arts/controlfiles/testdata/'
data = generate_atmos_arts(dataset_path, save_path)
ws.ReadHITRAN(filename='/home/mandy/Github/MiAtmosphere/HITRAN/ALL.par',
hitran_type="Online", abs_lines=ws.abs_lines)
# =============================================================================
# select/define agendas
# =============================================================================
ws.LegacyContinuaInit()
ws.PlanetSet(option="Earth")
# cosmic background radiation
ws.iy_space_agendaSet( option="CosmicBackground" )
# sensor-only path
ws.ppath_agendaSet( option="FollowSensorLosPath" )
# no refraction
ws.ppath_step_agendaSet( option="GeometricPath" )
# main agenda
ws.iy_main_agendaSet( option="Clearsky")
# water agenda
ws.water_p_eq_agendaSet()
# surface agenda
ws.iy_surface_agenda = iy_surface_agenda
ws.ArrayOfStringSet( ws.iy_aux_vars,
[ "Optical depth",
"Radiative background"
] )
ws.propmat_clearsky_agenda=propmat_clearsky_agenda
# gas scattering agenda
ws.gas_scattering_agenda = gas_scattering_agenda
ws.NumericSet( ws.ppath_lmax, 1e10)
# =============================================================================
# basic conditions
# =============================================================================
# Postion and line-of-sight of sensor
sensor_pos = np.array([[600e+3, 0., 0.]])
# Sensor looking direction in zenith angle (0 = upwards, 180 = downward) and
# azimuth angle ( 0 = North, 90 = east)
sensor_los = np.array([[180, 0]])
ws.sensor_pos = sensor_pos
ws.sensor_los = sensor_los
ws.VectorSet(ws.rte_pos2, [])
# 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
# Set frequency
#wavelengths = np.linspace(1250e-9, 1177e-9, 74)
#wavelengths = np.linspace(700e-9, 400e-9, 74)
wavelengths = np.linspace(1178e-9, 1177e-9, 2)
f_grid = c / wavelengths
ws.f_grid = f_grid
####
# set a simple blackbody sun
ws.Touch(ws.stars)
ws.starsAddSingleBlackbody(distance=1.495978707e11, latitude=0., longitude=0.)
ws.Print(ws.stars, 2)
# Reference ellipsoid
ws.refellipsoidEarth(ws.refellipsoid, "Sphere")
# 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
# Atmospheric dimensionality and lat/lon grids
nlat = 3
nlon = 5
ws.VectorNLinSpace(ws.lat_grid, nlat, -90., 90.)
ws.VectorNLinSpace(ws.lon_grid, nlon, -180., 180.)
ws.AtmosphereSet3D()
# 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")
ws.propmat_clearsky_agendaAuto()
ws.AtmFieldsCalcExpand1D()
#Get ground altitude (z_surface) from z_field
ws.MatrixSetConstant(ws.z_surface, nlat, nlon, 0.)
ws.ArrayOfStringSet(ws.surface_props_names, ["Skin temperature"])
#ws.Tensor3SetConstant(ws.surface_props_data, 1, nlat, nlon,
ws.t_field.value[0,0,0])
ws.Tensor3SetConstant(ws.surface_props_data, 1, nlat, nlon, 1e-16)
# #print(ws.t_field.value[0,0,0])
# Set surface relectivity
#ws.surface_reflectivity = np.array([[[1.]]])
ws.surface_scalar_reflectivity = [1]
# No jacobian calculations
ws.jacobianOff()
# No particulate scattering
ws.cloudboxOff()
# No sensor model
ws.sensorOff()
ws.StringSet( ws.iy_unit, "1" )
ws.Extract( ws.z_surface, ws.z_field, 0 ) # z_field is all the altitude and
z_surface is altitude at the surface
ws.Extract( ws.t_surface, ws.t_field, 0 ) # t_field is all the temperature
ws.WriteXML( ws.output_file_format, ws.z_field )
ws.WriteXML( ws.output_file_format, ws.t_field )
#Switch off gas scattering
ws.IndexSet(ws.gas_scattering_do, 0)
#Switch on stars
ws.IndexSet(ws.stars_do, 1)
# Check model atmosphere
ws.propmat_clearsky_agendaAuto()
ws.propmat_clearsky_agenda_checkedCalc()
ws.atmfields_checkedCalc()
ws.atmgeom_checkedCalc()
ws.cloudbox_checkedCalc()
ws.sensor_checkedCalc()
ws.lbl_checkedCalc()
# the actual simulation
ws.yCalc()
# output iy file
ws.WriteXML(ws.output_file_format, ws.y)
________________________________
From: Manfred Brath
<manfred.br...@uni-hamburg.de><mailto:manfred.br...@uni-hamburg.de>
Sent: Monday, October 17, 2022 5:56:40 PM
To: Xia Mengqi;
arts_users.mi@lists.uni-hamburg.de<mailto:arts_users.mi@lists.uni-hamburg.de>
Subject: Re: Fwd: [arts-users] Direct radiation is subtracted when it should not
Hello Mengqi,
Am 17.10.22 um 16:33 schrieb Xia Mengqi:
Hi Freddy,
Thank you so much and this is very helpful! Just to make sure I fully
understand how to use it in the code -- According to ARTS output, it seems I
need to provide the skin temperature as well. I noticed that in one provided
example it has "
ws.ArrayOfStringSet(ws.surface_props_names, ["Skin temperature"])
ws.Tensor3SetConstant(ws.surface_props_data, 1, nlat, nlon,
ws.t_field.value[0, 0, 0])"
I'm wondering if there is a simple way to do this for 1D.
so far you cannot use a 1d atmosphere for simulation with a direct source like
the sun because the atmosphere dimension and (radiative transfer) geometry are
coupled in ARTS. Since you have a zenith and an azimuth dependency for
simulation with a direct source, you have to use a 3d atmosphere in ARTS as
simulation of 1d atmospheres have only zenith dependency in ARTS.
Also, is it possible to just not include surface emission?
No, but you can set the surface temperature to a small value greter than 0 K.
This would have a similar effect.
Cheers,
Freddy
--
----------------------------------------------------------
Dr. Manfred Brath
Radiation and Remote Sensing
Meteorological Institute
Universität Hamburg
Bundesstraße 55
D-20146 Hamburg
Room 1535
Tel: +49 40 42838-8786
