Minutes of the third International Radiative Transfer Modeling Workshop
============================================================================
========== ===========
========== IRTMW01- 10/11 October, 2001 ===========
========== ===========
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Chairmen:
---------
Stefan Buehler
Patrick Eriksson
Joachim Urban
Carmen Verdes
============================================================================
Participants
------------
Chalmers:
Patrick Eriksson
Carlos Jimenez
Donal Murtagh
IUP:
Stefan Buehler
Carmen Verdes
Shreerekha T.R.
Claudia Emde
Viju O. John
Nikolay Koulev
Oliver Lemke
Thomas Kuhn
Jungang Miao
DLR:
Franz Schreier
UBordeaux:
Jo Urban
KF Karlsruhe:
Gerhard Kopp
Fujitu FIP Corporation:
Chikako Takahashi
CRL:
Yasuko Kasai
Satoshi Ochiai
NASDA/EORC:
Sho Tsujimaru
Uni Bonn:
Ariane Thiele
Kokugakuin Univ.:
Kazuo Shibasaki
-----------------------------------------------------------------------------
participating models:
ARTS IUP/Chamlers 1A 1B 3down 3limb
3up
CRL Satoshi Ochiai 1A 1B 3down 3limb
3up
Moliere (MOLIERE-4.86) Jo Urban, UBordeaux 1A 1B 3down 3limb
3up
DLR Franz Schreier 1A 1B 3down 3limb
3up
SMILES Simulator "SS","FIP" Yasuko, Chikako 1A 1B 3down 3limb
Sho's model "EORC" Sho 1A 1B 3down
Karlsruhe "FZK" Gerhard Kopp 1A 1B 3down
3up
-----------------------------------------------------------------------------
SEE THE VERY END FOR SUMMARY OF FINDINGS AND THINGS TO DO!
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
CASE 1A Session Species absorption
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
GENERAL ITEMS:
==============
- Voigt line shape calculation should be compared for a specific case
of one line. Test case will be defined by IUP.
- partition functions for isotopes should be checked
- it seems that for O2 the isotope has as strong lines as the main
isotope - it has to be checked. In HITRAN96 is an error for the
isotopic lines of O2. In HITRAN00 this error
is removed for the sake of introducing other errors (H2O
isotopes?). See comment in ARTS from Axel.
- weak NO lines (150.19 and 150.57) should be omitted.
- all models should include the (f/f_o)^2 in the lineshape
- pressure shift should be included (only non-zero for HCl).
Overview of absorption comparison
------------------------------------
1) H2O22GHz ARTS-Moliere Moliere is higher in the wings
CLO501GHz ARTS-Moliere good agreement
O3625GHz ARTS-Moliere good agreement
2) H2O22GHz ARTS-CRL
O3625GHz ARTS-CRL good agreement
CLO501GHz ARTS-CRL good agreement
3) H2O22GHz ARTS-DLR problem >5% difference
O3625GHz ARTS-DLR
CLO501GHz ARTS-DLR
4) H2O22GHz ARTS-SS 10% difference in the wing
O3625GHz ARTS-SS 10-25% diff.
CLO501GHz ARTS-SS 5% diff. in the lower band side
5) H2O22GHz ARTS-FZK very large difference at the band ends!!
O3625GHz ARTS-FZK 2% diff.
CLO501GHz ARTS-FZK 15% diff. in the lower band side
Detailed discussion of absorption comparison ARTS-Moliere
----------------------------------------------------------
H2O-22GHz
-10e-3 offset in both band wings at higher altitudes
PE: Voigt implementation maybe different
CLO501GHz
PE: Voigt implementation maybe different indicated by the features in
the differences
HNO3544GHz
high altitudes diff. in the lower band end
HCL626GHz
asymmetric differences around the line center 1-2% level
PE: center frequency shifted?
Window150GHz
At 150.19 and 150.57 there are lines missing in the ARTS "window"
calculations
CO576GHz
strange feature around the line center
!!LOOK into the pressure shift calculation in ARTS!!
CLO
major difference in the line center
Detailed discussion of absorption comparison ARTS-CRL
----------------------------------------------------------
H2O22GHz
diff not pressure depended
CRL uses here Lorentz line shape
ARTS VoigtKunz-quadratic without mirror line
Window89GHz
30% diff. with some structure in the diff.
O3110GHz
line shape diff. seen, (f/f_o)^2 not in CRL model
O2118GHz
diff. in the band wings are a straight line
also diff. in the line center
Window150GHz
lines not missing like in Moliere (-> Moliere added som lines?)
HCN354GHz
not special diff.
CLO501GHz
in the band wings are the largest diff.
N2O502GHz
at highest alt. 20% diff. in the line wing
HNO3544GHz
diff. in the lower band wing
CO576GHz
8% diff at lower altitudes
O3625GHz
0.5% diff. in the lower band wing
HCL635GHz
see pressure shift entry in the HITRAN catalog
CLO650GHz
50% diff. in the band wings!!
investigation of the Voigt implementation of CRL because this
calculation is especially implemented by Satoshi himself, so one can
compare this implementation with the standard calculations
(e. g. Kuntz)
Detailed discussion of absorption comparison ARTS-DLR
------------------------------------------------------
DLR is calculating on a wavenumber grid not on a frequency grid.
FS:
I guess this should not make any difference in the spectra sent
to Bremen: indeed the cross sections have been calculated on a
wavenumber grid, but have been saved on file as cross sections vs
frequency, i.e. the x-axis has been scaled by 29.99792458
(actually the hitran line data are in wavenumbers, too,
hence everybody had to convert to frequencies at some stage
of the exercise!)
General discrepancy:
FS: suggests that the order of the spectra is simply wrong so that in
the comparison in fact two spectra of different (p,T) are compared.
PE: pressure broadening different to ARTS, unit conversion problem?
FS: will check this point
Window89GHz
in the line large diff. 25%
O3625GHz
in the line wing up to 8%
Detailed discussion of absorption comparison ARTS-SS
-----------------------------------------------------
VoigtKuntz line shape used in SS without the (f/f_o)^2 factor,
conversion frm F77 to C made by Chikako herself
H2O-22GHz
10% diff. in the lower band wing.
Window89GHz
good agreement
O3110GHz
diff. most in the line center 60% at 18 km
O2118GHz
line center 30% diff at 55 km altitude.
Window150GHz
specific lines show up in SS (300% diff. max.) which are not in ARTS
(149.5, 150.3
GHz) especially at 55 km altitude.
H2O183GHz
At 183.8GHz a remarkable diff. of 150% , also difference at 182.7 and
182.2.
Detailed discussion of absorption comparison ARTS-FZK
------------------------------------------------------
H2O22GHz
with continuum calculated
no real comparison possible
Window89
diff. up to 80%
O2118GHz
in the line center diff. small but in the line wing very large
diff. 100%
VVW line shape function used in FZK.
center line missing in FZK?
CLO501GHz
jump in the line wings symmetric around the line center at high
altitude - why?
N2O502GHZ
same feature as for CLO501 at high altitude
HNO3544GHz
up to 60% diff. at lower band wing, 20% in the line range at higher
altitudes.
CO576GHz
some sort of cut off in the line shape? Same feature as for the other
species at high altitude.
O3625GHz
Same feature as for the other species at high altitude.
CLO649GHz
strong offset seen
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
CASE 1B Session continuum absorption
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
GENERAL ITEMS:
==============
- problem with H2O isotopic lines around 550GHz. Compare with Moliere
(Phillip Baron) and with JPL and HITRAN00.
Detailed discussion of continuum absorption comparison ARTS-CRL
--------------------------------------------------------------------
O2 included in CRL calculations
CRL has simply taken the MPM89 model and changed the line catalog to
MPM93. So the continuum term is still MPM89.
No difference in CRL and SS
Detailed discussion of continuum absorption comparison ARTS-Moliere
--------------------------------------------------------------------
ask Phillip Baron about the strong isotopic H2O lines at 547 and 552
GHz. Error in the MPM93 but what is changed actually in Moliere?
How to fix this error? Comparison
Isotopic ratio is missing in MPM93.
Outside of this, the two models are in very good agreement.
Detailed discussion of continuum absorption comparison ARTS-EORC
--------------------------------------------------------------------
MPM89 continuum used together with MPM93 lines, so directly
comparable.
Detailed discussion of continuum absorption comparison ARTS-FZK
--------------------------------------------------------------------
MPM89 is used by FZK for this calculations so not directly comparison.
Some sort of cut off in the FZK line shape?
Detailed discussion of continuum absorption comparison FZK-EORC
--------------------------------------------------------------------
large differences, but not sure where they come from.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
CASE 2 Session species absorption comparison
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
GENERAL ITEMS:
==============
- dry air continua to be checked in ARTS too high! (-->TKS)
- pressure shift check in ARTS, Verdandi (definitely an error), Moliere.
Is there a sign for the pressure shift data in the HITRAN catalog?
Check.
- HNO3@544GHz error in HITRAN96 - check
- ARTS O2118 line check which model is actually used for this
comparison in arts?
- it seems to exist a "line shape problem" between the different
implementations. So this basic stuff has to be in agreement before
further calculations are performed.
Detailed discussion ARTS-Moliere
--------------------------------------------------------------------
H2O22GHz
5% global difference outside of the line center range.
peak diff. at 21.95 and 22.3 GHz of 25% and 10%, respectively.
Window89
large difference, in general 400%!! -> WHY?
H2O183GHz
line centers are shifted due to HITRAN-JPL difference.
HCN354GHz
ok
CLO501GHz
ok
O3625GHz
at 625GHz large diff.
HCL625GHz
features at 626 and 626.2 GHz, due to additional lines or isotopic
ratios, pressure shift?
Detailed discussion ARTS-EORC
--------------------------------------------------------------------
H2O22GHz
line shape differences?
different continuum seen in the millimeter region
differences between JPL and HITRAN catalogs seen
Detailed discussion ARTS-FZK
--------------------------------------------------------------------
dry air continuum differences might cause the large differences in the
window regions. ARTS should be checked.
line shift seen, but sure which implementation is correct. This has to
be checked.
line wings perhaps differently modeled.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
CASE 3 Session Radiative transfer intercomparison limb case
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
GENERAL ITEMS:
==============
- see if there is an error in the interpolation scheme in ARTS.
Detailed discussion ARTS-Moliere
--------------------------------------------------------------------
f=495-510GHz
differences in the line center regions are seen of up to 8K.
probably the interpolation of the abs. coeff is the main source of the
difference
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
CASE 3 Session Radiative transfer intercomparison downlooking case
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
GENERAL ITEMS:
==============
interpolation problem, conversion problem and ground model reflection
are the major three different points.
Set the ground emissivity to one for avoiding reflection to get a
better setup for further comparisons:
- sigma = 1
- output should be in `true' (Planck) brightness temperature
Detailed discussion of comparison without sensor ARTS-Moliere
--------------------------------------------------------------------
80-200GHz
Moliere has no reflection but emission of the ground, ARTS has both
terms.
Detailed discussion of comparison without sensor ARTS-CRL
--------------------------------------------------------------------
80-200GHz
CRL has no reflection but emission of the ground, ARTS has both terms.
Detailed discussion of comparison without sensor Moliere-CRL
--------------------------------------------------------------------
80-200GHz
diff. of 1K at 89 channel, 3K at 150 GHz and 4K at 183 GHz.
Difference of RT in the optical thick region.
Conversion to brightness temperature is done by Rayleigh-Jeans in the
case of CRL and Planck in the case of Moliere.
PE: suggests that the difference is due to interpolation
SB,VJ: the conversion from Planck to Rayleigh-Jeans is the cause for the
difference
SB: another thing must be different since the difference can not only
explained by the conversion.
Detailed discussion of comparison with sensor ARTS-Moliere
-----------------------------------------------------------
no real difference compared to the subcase without the spectrometer
Detailed discussion of comparison with sensor Moliere-CRL
-----------------------------------------------------------
difference in the sensor model compared to the subcase
without the spectrometer
The sensor model should average both sidebands!
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
CASE 4 Session RT comparison
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
GENERAL ITEMS:
==============
Because we have shown that in both absorption and RT are remarkable
differences, the case4 comparison will be of no use. So
this case will be redone after the mentioned differences are clarified.
Minutes of the Third International Radiative Transfer Modeling
Workshop 2001
===============================================================
Minutes of 11 October 2001
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
Special Session: recalculations
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
General Items
=============
1.) Patrick
-----------
in ARTS the interpolation is actually done linearly in pressure and not
in log(p) as thought yesterday (in one place in the RT calculation).
Different results are seen for different interpolation schemes for
sparse grids. So one has to calculate the integral on a dense grid to
avoid differences due to different interpolation schemes.
Franz is doing his interpolation with the quadrature method ("trapez"
rule or splines) for the calculation of the optical depth.
For sparse altitude grids one should see differences to ARTS.
Franz: Added comments
---------------------
Interpolation and quadrature (= numerical evaluation of definite integrals)
are different things.
I am using standard methods of numerical mathematics to solve the
integrals showing up in the radiative transfer problem,
i.e. beer's law in an inhomogeneous atmosphere (here just one molecule)
T(v,s) = exp [-integral_0^s a(v,s') n(s') ds']
where v is wavenumber or frequency
a is the absorption coefficient
n is the molecular number density
s is distance along line of sight
and the 'schwarzschild equation' (ignoring a source/background term)
I(v) = integral B(T(s),v) [dT(v,s)/ds] ds
So in general a quadrature rule approximates
integral_a^b f(x) dx = sum w_i f(x_i)
where w_i and x_i are the nodes and weights which depend on the
quadrature rule actually used.
For example, trapez quadrature is simply
integral_x0^xN f(x) dx = sum 0.5 (x_i-x_{i-1}) [f(x_i) + f(x_{i-1})]
The quadrature rules I am using to solve beer and schwarzschild are
trapez, method of overlapping parabolas, and a method based on a
spline representation of the integrand. These methods work
for arbitrarily spaced abscissas=nodes (in contrast, the standard
simpson would require the x_i to be spaced equidistantly).
"My" nodes are defined by the altitude grid points where p, T, and
gas densities are given. Thus in case of up or downlooking, the path
variable s along the line of sight is identical to the altitude z
(maybe except for its orientation), and in case of general slant pathes
s is just z with a factor cos(angle). For limb its a little more
complicated, certain altitudes show up twice along the line of sight,
i.e. to the left and right of the tangent point.
Anyway, the integrals are evaluated exactly at these grid points s_i,
and there is no interpolation required to solve these integrals.
(However, as mentioned in Delmenhorst, an interpolation will be made
in case the tangent height is between two altitude grid points.)
Except for this special case of intermediate tangent points,
interpolations are used in mirart at just two occasions:
If atmospheric data are read from different files (each with its
own altitude grid), the data are interpolated to one common grid.
And:
As cross sections are calculated on a wavenumber (frequency) grid
which is unique for each level (p, T) and molecule, the cross
sections are interpolated to common (i.e. the finest) grid
before the radiative transfer calculation (abs. coeff.,
transmission, radiance) is started.
I should also mention that there is no interpolation done for
finite field of view simulations (again with the above mentioned
exception).
2.) Gerhard
-----------
In the FZK model there was a rudimentary Voigt function implemented
which was switched on at hight altitudes. This caused the featured
differences compared to ARTS.
3.) Satoshi
-----------
Case 1A difference: there are still remarkable differences remaining
Case 1B difference: Also.
4.) Jo
-------
extra lines in Moliere two NO lines were taken into account by Moliere
but not in ARTS. This was just a misunderstanding in the way to
perform the comparison.
Comparison of ARTS and Moliere for the Odin FM comparisons study.
Then diff. is of the order of 5% or lower for the frequency range
around 500 GHz.
Moliere-Odin operational code differences are very small, negligible.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
Session: Case 3 RT intercomparison limb looking
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
General Items
-------------
- specify the cosmic background (yes/no) more clearly in the
comparison instructions
- specify the Earth radius more clearly in the
comparison instructions
- specify the tangent altitudes for the limb cases more clearly
in the comparison instructions
- finer absorption grid calculations for the further comparisons
- true Planck brightness temperature is the reference for the future
comparisons
==> repeat the calculations with these new specifications
Detailed discussion ARTS-Moliere
--------------------------------
495-510GHz
differences of 10K at lower altitudes (->interpolation?)
PE: do the calculation for a fine grid to see more clearly the
difference
The cosmic background is not included in Moliere, so in the windows
the diff has an offset of the cosmic background.
Detailed discussion ARTS-CRL
--------------------------------
495-510GHz
differences up to 20K can be seen in the line wings, while in the line
center the diff. is very low.
The differences are all going into one direction. Perhaps the Earth
radius is differently introduced since only the observation angles are
provided for this comparison.
Detailed discussion ARTS-DLR
--------------------------------
495-510GHz
differences are very high, but the structures of the differences are
so that one can assume a unit conversion problem or a mismatch of the
tangent altitudes.
Detailed discussion ARTS-SS
--------------------------------
495-510GHz
differences are highest in the line center up to 20K, but in the line
wing the difference is small.
Comparing SS with Moliere shows also high differences in the line
center but also some remarkable diff. in the line wings (offset).
The cosmic background is not included in SS.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
Session: Case 4 RT intercomparison limb looking
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
General Items
-------------
Omitted, sine basic problems have to be resolved first.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
Session: Case 3 RT intercomparison up looking
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
General Items
-------------
- DLR recalculate the stuff with appropriate units of abs. coeff.
- CRL recalculate the stuff with appropriate platform hight.
- zero degree error in FZK.
Detailed discussion ARTS-Moliere
--------------------------------
142GHz
diff. (<0.4K) in the wings perhaps the cosmic background which is in
ARTS but
not in Moliere calculated.
Additionally the interpolation can cause some of the difference.
Detailed discussion ARTS-CRL
--------------------------------
offset of 50K can be seen. Causes: the observation platform altitude was
different
in both calculations.
Detailed discussion ARTS-DLR
--------------------------------
abs. coeff. conversion was not done for the DLR input. DLR needs 1/cm
and given were 1/m. Otherwise good agreement.
However, the redone the calculations during the morning session
(i.e. included the 1/m to 1/cm conversion in my code) and the comparison carried out during the lunch break showed consistent results withing a Kelvin
Detailed discussion ARTS-FZK
--------------------------------
diff. of 1K in the line center and approx. zero in the line wing for
zero degree observation angle. All the other observation angles are
in good agreement. Some interpolation differences in the line center
region are seen
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
Session: Case 3 RT intercomparison up looking sensor part
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
General Items
-------------
Detailed discussion ARTS-Moliere
--------------------------------
good agreement (diff in the line center 0.3K in the line wing 0.38K)
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
Session: Case 4 RT intercomparison up looking with sensor
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
General Items
-------------
- ARTS should calculate this case with a monochromatic frequency grid of
just
1MHz spacing. Also the sensor has to be refined to smaller channel
width in the line center. ==> finer frequency grids!
- the specifications for this case should be more clear. Also which
species should be included in th atmospheric scenario (H2O, N2, O2,etc.)
Detailed discussion ARTS-Moliere
--------------------------------
Cosmic background included in Moliere here. Diff 2K in the line
center. One can see the different line data base in the plot because
of the different line center frequency. One should JPL for this case
and not HITRAN because of its more accurate center frequency.
Detailed discussion ARTS-CRL
----------------------------
offset of approx. 2.5K and the line center frequency is slightly
shifted and pressure broadening is might be different,
different continua treatment?
Detailed discussion ARTS-DLR
----------------------------
very good agreement, only in the line center a diff. of the order of
1K can be seen. Same spectroscopical input is used for ARTS and DLR,
also Voigt is used in both models. But DLR uses the CKD continuum.
Because the sensor with 25MHz frequency grid spacing (sparse in this
case), so this can explain also some differences. Also the sensor is
to broad, smaller channel width should be used.
Detailed discussion DLR-FZK
----------------------------
Problem, oxygen is switched off in the calculations in case of FZK, so
this explains the offset of some Kelvins.
No sensor model included in FZK model, so the convolution is done by
Carmen with her sensor model.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
Session: summary/discussion
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
Case 1 Absorption
------------------
a. line shape functions
- IUP will create a new case 0, where the Voigt function will be
tested. Constant T=296K (to avoid the line strength
temperature conversion) and for constant T=250K (for partition
function
implementation test), pressure changes, but VMR const., only one
line. The differences should be below 10^-4.
- The (f/f_o)^2 factor should be included in the lineshape.
b. pressure shift
- sign of the shift parameter (HITRAN ?, Verdandi ?)
- implementation in the different models
- The given catalog contains a shift for HCl, which should be
taken into account in the simulations.
c. errors in the line catalogs
- O2 isotopic lines too strong in HITRAN96, also water vapor isotope
problems are known in HITRAN00.
- H2O-Isotopic lines 550GHz in MPM93, PE will ask P. Baron
Franz: added comments
---------------------
O2 isotopic lines too strong in HITRAN96
Birger and I had noticed these strong O2 isotope lines already when
we analyzed the DLR heterodyne OH spectra in the far infrared.
After comparsison with JPL O2 data we concluded that the isotope
abundance factor is simply missing in the O2 isotope lines,
so it is a very "systematic" error.
d. line exclusion
- exclude to NO lines from this comparison (see Moliere's extra
lines)
e. set the self line broadening term to the foreign broadening term if
there is no information in HITRAN.
f. target: below 0.1%
Case 2
------
- addressed to IUP: try to be realistic in the specifications for this
case. (Also applies to the other models of course.)
- also make a reasonable mix of the continua and line absorption terms
in ARTS.
Case 3 limb
-----------
- viewing direction should be specified on a unique way (tangent
altitude, Earth radius)
- splitting: to determine the interpolation another calculation should
be done with a very fine grid of 100m. Absorption and temperature
will be provided on this fine grid by IUP.
- units of the output should be in true Planck brightness temperature.
- cosmic background should be implemented in the calculations,
T=2.735K.
- target: the differences for the fine grid comparisons should be below
1.0%
and below 1K.
Case 3 down-looking
-------------------
- reflectivity neglected, the emissivity will be set to 1.0 to avoid
discrepancies.
- calculation should be done with a very fine grid of 200m.
- units of the output should be in real Planck brightness temperature.
- specifications of the sensor model: perfect double-sideband receiver.
- 130-180 degree to be calculated (one side of the scan).
Case 3 up-looking
-----------------
- units of the output should be in real Planck brightness temperature.
- cosmic background should be implemented in the calculations,
T=2.735K.
- one should go to higher zenith angles (0-80 degree), elevation
angles between 10 and 90 degree.
- more realistic width of the sensor channels (1MHz).
- monochromatic frequency grid narrower that the sensor frequency grid.
- no refraction.
Case 4
------
- Be as realistic as possible, this means also that each model should
use its own optimized way of calculation.
- line spectra
- continua
- refraction
- cosmic background.
- One should be go to higher zenith angles (0-80 degree), elevation
angles between 10 and 90 degree.
%%%%%%%%%%%%%%%%%%%%%
Session ARTS overview
%%%%%%%%%%%%%%%%%%%%%
SB hints on ARTS free download. Comments are very welcome to improve
the code and the portability.
Next year next workshop at Bredbeck probably, then in summer.
- Thank you for coming!
============================================================================
minutes written by Thomas Kuhn, iup, 10/11.10.2001
============================================================================
