Minutes of the fifth International Radiative Transfer Workshop, July 2003

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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
   

    
            
    
       

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