Hi Frank, Hi all,
first, I agree with Patrick, it's easier to provide suitable support when
you provide information which (major) version you use. A lot has happened
in development (ie 2.3) since the release of the last stable version (ie
Then, however, I have to slightly correct Patrick - internal calculation of
pnd_field IS possible in 2.2 already. It's a limited number of
parametrizations available for that, but it includes the MH97 that Patrick
mentioned (see workspace method pnd_fieldSetup in v2.2 online doc).
Since you mentioned absorption - there is a bunch of different ways with
different complexity and level of simplification to handle/consider
- when absorption/emission is sufficient, then hydrometeors can be handled
as an absorption species using one of the hydrometeor continuum models (see
continua.arts in controlfiles/general/ for available ones). these
hydrometeor continua are refractive index/permittivity-based, ie assume
Rayleigh particles. the hydrometeor field then goes as one field entry into
vmr_field (just as any other absorption species set in abs_species) and
should contain, I think, the mass concentration (kg/m3)
Pro: no scat_data and pnd_field needed.
- then there is an option to still only consider absorption/emission and
the hydrometeor species as an absorption species, but take the optical
properties from actual scattering property calculations, eg Mie or Tmatrix
calculations or even scattering databases; whatever you put into scat_data
(see Section "Absorbing particles" in the ARTS User Guide(s) and
propmat_clearskyAddParticles in the online documentation and for an example
controlfiles/artscomponents/absorption/TestAbsParticle.arts in v2.3 code
base - this should, with some adaptions for name changes between v2.2 and
v2.3 also work in 2.2; i just hadn't prepared an example yet back in the
Pro: Fast. Actual optical properties used.
- Finally, you can do actual scattering calculations using a range of
different scattering solvers. These all need scat_data and pnd_field
- Here pnd_field can either be prepared externally and just read-in
(example for this in controlfiles/artscomponents/doit/TestDOIT.arts*).
- Or you can calculate the pnd_field from hydrometeor mass (sometimes
also number) concentration or precip rates (which parameter field(s)
required depends on the bulk parametrisation used). This approach also
requires some meta data on the hydrometeor optical property (scat_data)
data (named scat_meta or similar, depending on the version...).
For examples see controlfiles/artscomponents/disort/TestDisort.arts* or
controlfiles/artscomponents/wfuns/TestWfunsHybCloudy.arts* in v2.3 (v2.3
currently has two different systems for internal pnd_field preparation. the
one in TestWfunsis the one that is newer, probably the nicer, but
definitely the one preferred and supported in the future)
Ragrding the input for pnd_field calculations,there's no "standard"
hydrometeor profile data (like the Fascode/AFGL standard atmospheres).
There's the different instances of ECMWF statistically-selected datasets in
arts-xml-data/planets/Earth/ECMWF/IFS/ that contain hydrometeor profiles.
But you probaly rather like to use your own ones, I assume.
For scat_data and scat_meta; there's examples in v2.3
controlfiles/testdata/scatData/. Also check user guide and online doc for
more formating info.
Atmlab (and typhon?) has functions to create scat_data (and scat_meta?)
from Mie and Tmatrix calculations. The ARTS scattering database comes with
an interface to prepare these from it's DDA-based contents.
* note these examples control cases/files are named after the use of
different scattering solvers. How to prepare pnd_field is independent of
the applied solver, ie you can combine solver and pnd_field preparation
approaches freely (almost: Hybrid solver only works with the approach used
in that controlfile).
On Tue, Nov 5, 2019 at 1:05 PM Patrick Eriksson <
> Dear Frank Werner,
> It makes me happy to hear that your are integrating ARTS into your code
> base. When we started ARTS, limb sounding was one of the main
> applications so it is very nice if ARTS gets used on limb sounders
> beside Odin/SMR.
> Let me start by asking if you are using v2.2 or a relatively recent v2.3?
> If v2.2: Then you have to create the "pnd_field" yourself and import
> data with e.g. ParticleTypeAdd.
> If v2.3: In this version you can work with particle size distributions
> (PSDs). Be aware that there was a first system, that now is replaced.
> The later version operates with particle_bulkprop_field. With this
> system you can give ARTS IWC-values and select some PSDs, such as the
> MH97 one that both Dong Wu and I have used for limb retrievals.
> In both cases, scattering data you either generate inside ARTS with
> T-matrix or take it from our "scattering database".
> Some brief comments. If you tell