Minutes of the fifth International Radiative Transfer Workshop,
July 2003
Monday
Tuesday
Wednesday
Thursday
Whole Week
Monday - 07-07-03
Minutes written by Viju Oommen John <vojohn@uni-bremen.de>
Mashrab Kuvatov <mashrab@sat.physik.uni-bremen.de>
1:30 - Welcome by Prof. K. Kuenzi
Announcements - Stefan
- B.B on Tuesday
- Inter-comparison draft will be distributed by Christian
- Introduction of the working group by the leaders
Introduction of participants
-----------------------------
1. Stefan Bühler - UB
2. K. Künzi - UB
3. Oliver - UB
4. Viju Oommen - UB
5. Carmen - UB
6. Mashrab - UB
7. Nathalie - UB
8. Claudia - UB
9. Emmanuel - UB
10. Christian - UB
11. Herman - Uni. St. Paulo, Brazil, Ground based radiometer for H20
12. Gerhard Kopp - Karlsruhe, Ground based radiometers
13. Claas - UB
14. Sho - UB, ASUR retrievals
15. Axel - UB
16. Cory - Uni. Edinburg, microwave limb sounding, cirrus scattering
17. Elisa - Bolonia, Water vapor retrievals from airborne instruments
18. Franz - DLR
19. Heike - Kiel, AMSU
20. George Schulz - Uni. Bonn, Microwave remote sensing
21. Erric - Astrophysics inst. Heidelberg
22. Dietrich - Bern uni, stratospheric water vapor, spectroscopy
23. Jana - DLR, radiative transfer including scattering
24. Sreerekha - UB
25. Mattias - Chalmers, Sensor modeling in ARTS
26. Patrick - Chalmers, RT,
27. Yasuko - CRL, Japan, SMILES
28. Thomas - UB
29. David Pollard - MO, UK, Airborne measurements, Helping assimilation group
30. Chikkako - Japan, Smiles
31. Arash - UB
32. Nikolay - UB
ARTS-1.1 - Claudia
- Modeling of atmosphere and cloud box for a three dimensional RT model
- Dimensionality of the atmosphere can be chosen(1, 2, and 3)
- successive order of scattering approach
- 1D test calculation
- Partic le shape is not so important around 320GHz region
- GS: Is particle shape important for polarization signals?
This should be checked.
3D Ray tracing - Patrick
- A complete forward model in one program
- Erric: Is refractive index far away from one? If it is far away from
one, RT equation has some fundamental problems.
PE: It is around 3% above one.
SB: This should be kept in mind if we go for planetary atmosphere
- Is the movements of the scattering medium is included(macroscopic
velocity filed)?
PE: Very high frequency resolution is needed
- GS: Can distribution of clouds be handled?
PE: Only one cloud is allowed at the moment
SB: This will be a straight forward extension
Sensor Modeling - Mattias Ekström
-
Atmlab - Patrick
- Bunch of matlab functions
- maths, physics, XML, graphics,.. matlab routines.
- can be downloaded from ARTS web-site.
Met Research Flight - David Pollard
- instruments: Deimos and MARSS - like AMSU (1, 2, 16, 17, 18, 19, and 20
channels)
- improvement of NWP models, implementation of scattering in fast RT models,
modeling of surface emissivity
- for land emissivity is 0.95; difficult to model for ice and snow
- determination: flying over different types of surfaces and measuring
radiances
EOS-MLS, clouds, and ARTS - Cory Davis
- implementation of scattering Monte Carlo method into ARTS
- validate against other ARTS scattering functions
- use ARTS to investigate possible shortfalls in existing EOS-MLS
cloudy-sky model
CLR - Yasuku Kasai
- JEM/SMILES: Band A, band B, band C; O3 and its isotopes, ClO, HCl,...
- Alaska project: tropospheric molecules and stratospheric molecules in IR range
- trajectory calculations from CO events
Forward model MIRART - Franz Schreier
- use of automatic differentiation (kind of preprocessor), it generates exact
derivative (ADIFOR for fortran)
ISAC CNR Bologna - Elisa Castelli
- development of algorithm to retrieve stratospheric chemical and
physical parameters using far infrared spectra
- data analysis of measurements recorded by SAFIRE and MARSCHALS instruments
- ENVISAT validation campaign08-07-2003 TUESDAY
Minutes written by Sreerekha T.R. <rekha@sat.physik.uni-bremen.de>
Chair - Carmen Verdes
- All the group works should start today
- Scattering group may splitted into two
Intercom-parison paper - Christian
- Discussions
DF: The reason for discrepancy in the BEAM model is the
proposed model is not used. It can be investigated that
how the error is propagated through different excersices
when adding lot of additional parameters
SB: For excersices 0,1, and three all the setup should be
similar for all the models.
DF: for case0 it can be written in the model that BEAM
has used different line shape
DF: One should not look only at the maximum discrepancy
but also to minimum and some average discrepancy, Franz
also has the same opinion.
SB: Standard deviation can be a good measure.
SB: Error with sensor integration is larger than without(fig. 13
and fig. 15), Why?
Franz: He will check
Sho: The frequency grid was not fine enough. The interpolation
methods can also lead to differences.
FS: Monochromatic grid supplied was very coarse
- There will be a small group discussing on Intercom-parison
today from 6-7pm.
- DF: JGR is not the best journal, JQSRT or radio science can be
alternatives.
- FS: JQSRT will be the best option
- Time for publication is less for Radio science
- The editor should be contacted before deciding to send the paper
- Strong suggestion to go for JQSRT
Multiple scattering - Jörg Shulz
- SB: Discussion in the scattering WG. very imp for the WG.
MIRART scattering implementation - Jana
-
Zeeman Implementation - Nikolay
- No discussion because of lack of time.
3D resonance - Eric Meinkoehn
-
Wednesday, 09-07-03
Minutes written by Claudia Emde <claudia@sat.physik.uni-bremen.de>
Carmen Verdes <cverdes@uni-bremen.de>
9:30 Welcome by Thomas
9:32 Stefan suggested to think about smaller WG
9:40 Axel v. Engeln: Intro to Radio Occultation
- Occultation of GNSS satellite
- Ducting (Radiance is reflected to Earth surface)
- Study background
- Limitations at lower altitudes
- Negative N Bias
- Setup
- Location/Altitude of Ducts
- Strength of dry ducting (without water vapor in atmosphere,
refractivity only temperature dependant)
- Altitude of ducts
- ECMWF data is useful tool for ducting studies
- Relevant ducting for RO appears mainly over sea
- Ducting events in CHAMP data in future study.
9:56 Gerhard Kopp: Potential of ground based mm-wave solar occultation
measurements
- Emission and absorption geometry
- Signature contrast of ClO
- Minimum background temperature 450K, if absorption signal is stronger
than emission signal (sun is appropriate, moon is too weak)
- Definition of relative signature contrast.
- Superiority of absorption measurements depends on elevation of the sun.
(> 20°)
- Balanced calibration
- Effect of antenna characteristics (90% coverage by sun)
- very close to ideal radiometer
- Problems
- large antenna, good pointing
- beam characteristics not well known
- Solar BT not constant
- additional baseline problems (damping element)
(DF:) similar problems with other instrument
(HB:) problems were not connected to solar occultation
- difficulties in putting up the antenna correctly
(SB:) solar spectrum signature?
- no additional lines, only flat blackbody spectrum
10:24 Sreerekha T.R.: Effect of cirrus clouds on microwave remote sensing
- Overview of projects, models (RTTOV, ARTS)
- Comparison of ARTS/RTTOV with AMSU data.
- Description of AMSU-B instrument
- Case study: AMSU-B data on 25-01-02, forecast fields from MET office
- ARTS input
- Problems when blackbody ground is assumed
- Setup of comparison
- Difference between time shifted data of 1 hour (significant)
- Difference between clear sky and cloudy fields (it's important to take
the correct time
- Effect of cloud is very small (about 1K) (200 microns particle size)
- about 6K difference for 500 microns particle size
- Emissivity issue (emissivity maps available, or different emissivity
models, e.g. FASTEM)
10:40 Coffee break
11:05 Sho: Smiles Retrieval
- Description of SMILES and ASUR instruments
- Instrument characteristics (differences and common properties)
- Retrieval of ASUR data in SMILES bands
- Simulation for AMSU and SMILES in Bands A, B, C
- Comparison of retrieval
- Large discrepancy near line center
possible reasons: frequency calibration ... probable
uncertainty in spectroscopic database ...
less probable
pressure shift of HCl ... probable
- Improvement in retrieval after including the pressure shift and
compensation of frequency calibration error (Band B)
- Retrieval in Band C works well even without corrections
(DF:) Not convinced about pressure shift
(PE:) Try to retrieved the frequency offset
11:30 Chikako: Estimation of the SMILES instrumental parameters
- Basic theory (OEM)
- Use the linear mapping for model parameters uncertainties
- Presentation of the model parameters: calibration error, sideband,
antenna, pointing knowledge, spectroscopic parameters, AOS knowledge
- Retrieval set-up
- Results: simulated measurements, retrieval results and instrumental
parameter errors (O3)
- The critical parameter is the antenna pattern
- Summary: the most critical is antenna pattern
better accuracy of spectroscopic parameters is required
11:52 Summary of working groups
- AMSU WG
- Participants: D. Pollard, H. Hauschildt, N. Courcoux, Viju Oommen
John, A. Houshangpour, C. Melsheimer, M. Kuvatov, Y. Kasai
- Different formulae to calculate Es
- Different RH
- ARTS vs. AMSU
- Problems: Deviation in Ch-18 (possibilities: cloud cases,
large viewing angle,RH is not correct)
- Validation over water
- Emissivity model (implementation)
- LWP retrieval
- Joerg: email some references (?). Look on the AQUA webside.
- Spectroscopy WG:
- Participants: C. Verdes, J. Mendrok, F. Schreier, N. Koulev,
E. Castelli, H. Berg, E. Brocard, G. Kopp, A. von Engeln, T. Kuhn
- Partition functions (TIP, new HITRAN, JPL, ATMOS)
- ATMOS: vibrational modes are included
- Database: BEAMCAT
- Line shape/Continua
- Continua implemented in MIRART
- Galatry Line shape
- Franz provides some references
Elisa: Contact J.M. Eland about intensity correction
- ARTS WG:
- Participants: C. Davis, J. Mendrok, Y. Kasai, M. Ekström, C. Emde,
O. Lemke, P. Eriksson, C. Takahashi, C. Teichmann, S. Bühler,
E. Meinköhn
- single scattering Database (current implementation in ARTS,
include temperature or refractive index)
- Monte Carlo approach to solve RTE
- Successive order of Scattering method
- Stefan: keep in mind to give some suggestions on the WG
- Lunch
Thursday, 10-07-03
Minutes written by Axel von Engeln <engeln@uni-bremen.de>
9:30 Working Group Summaries:
- Installation of ARTS Group (12:Oliver):
- Participants: O. Lemke, C. Takahashi
- Successful install
- Use of Views (7:Stefan):
- Participants: S. Bühler, O. Lemke, M. Ekström, H. Berg,
G. Kopp, N. Koulev
- Tutorial on Matrix Views, etc. See User Guide
- Sparse Matrix, make views sense with sparse matrix?
Stefan: no
- Dietrich: Matlab Clone Octav? Might be capable to
handle sparse matrix.
----> Action Item: Check Octav/other matlab clones for this
- Scattering Group (1:Claudia):
- Participants: C. Emde, C. Davis, E. Meinköhn, J. Mendrok,
C. Teichmann
- Setup for comparison between Monte Carlo and successive
order of scattering:
- 2 Cloud scenarios: weak, strong, cloudbox 1Deg x 1Deg,
6-12km, cloud from 9-11km, stokes dim=2
- Discussion about Monte Carlo
- Use of Agenda in connection with optical properties
- Grid optimization (8:Erik):
- Participants: E. Meinköhn, F. Schreier, P. Eriksson, C. Emde,
C. Teichmann, J. Mendrok, C. Verdes, D. Feist, E. Brocard
- freq opt:
- Patrick: some suggestions
- Dietrich: 99% reduction possible
both message use a priori knowledge on line center, problem
with macroscopic velocity field
- Spatial Grid:
- Erik: Finite element discretization
----> Action Item: Erik-Mail homepage on library
- Ordinate Grid:
- a priori knowledge
- other methods
- Workshop in Heidelberg on Multidimensional RT problems
24-26 of September 2003
- Retrieval (3:Sho):
- Participants: S. Tsujimaru, C. Verdes, F. Schreier, E. Castelli,
P. Eriksson, G. Kopp, H. Berg
- Baseline problem: baseline ripples, Qpack (polynomial),
Karlsruhe (sin curves)
- Regularization:
- Formal relation between OEM and Twomey-Tikonov by correlation
length
- L-curve method
- Comparison of different regularization
- positivity constraint on x
----> Action Item: Franz-mail paper on this
- Selection of retrieval grid
- finer grid require correlations to get same results
as coarse grid
- Choice of a priori and covariance
- Frequency offset retrieval
- Sensor Matrix modeling in ARTS (2:Christian):
- Participants: P. Eriksson, M. Ekström, S. Buehler, C. Melsheimer
- how model full Stokes vector with antenna pattern:
- rotate Stokes vectors by angle to match antenna pattern
specification
- how to handle in ARTS (Patrick):
- not possible in H matrix
- first transform to sensor frame
- then apply additional matrix multiplication
- Cloud resolving models (4:Sreerehka):
- Participants: Sreerekha T.R., C. Davis, J. Schulz, H. Hauschildt,
C. Melsheimer, D. Pollard, T. Kuhn
- KNMI, Wisconsin, MeteoFrance
- Measurement campaigns: Emerald I, II, Crystal..., ARM,
TOGA. COARSE, ...
- Van der Wals Complexes/Continuum (7:Thomas):
- Participants: T. Kuhn, Y. Kasai, N. Koulev, E. Brocard
- S. Solomon calculated the impact
- Yasuko measured O2-O2 in lab, publication?
- Continuum:
- Lab fit not in agreement with atm measurements
- Surface Emissivity/AMSU Validation (9:David):
- Participants: D. Pollard, Sreerekha T.R., H. Hauschildt, Viju O.-J.,
M. Kuvatov, J. Schulz, C. Melsheimer, A. von Engeln, A. Houshangpour,
N. Courcoux
- Surface Emissivity:
- Ocean: good models, except for high wind speed
- Land: 0.95?, some models for f < 50GHz, NOAA have maps
with low temporal resolution at 85GHz
- Ice/Snow: no reliable models
- AMSU Validation:
- Cloud clearing of clear sky: Use super saturation
wrt to ice
- Discrepancies between UK/Germany: different cloud
characteristics
- Future work: validation at mores sites, emissivity
calculated
- ESA proposal (Joerg)...
- Intercomparison (10:Franz):
- Participants: F. Schreier, C. Melsheimer, D. Feist, G. Kopp,
C. Verdes
- the never-ending story of the paper
- continue this study, e.g. weighting fcts, atmospheric data
- Dietrich: Lautlos field Campaign (H2O, 0-35km), use these
data for further comparison? e.g. with ODIN
----> Action Item: Look at Lautlos data once it is available
11:30 Feedback of the Participants
- Positiv: small, informal, working groups, good overview in talks,
lot of off-line talks
- Suggestions: smaller working groups, better organized,
less code oriented ARTS discussion (maybe add 1
extra ARTS day), extend intro of participants (1-2 slides)
- Negativ: Initial working groups were too large, internet access,
code oriented ARTS discussions, food and drinks
12:00 Future Plans
- Web collection of workshop material (minutes, presentations, paper
suggestions, web page info, working group minutes and participants)
---> Action Item: Oliver - Email alias with participants
- Proceedings with talk material?
12:10 Close
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