Minutes of the sixth International Radiative Transfer Workshop, June 2004

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BREDBECK  2004  Minutes
=======================


Thursday, 24/06/04

Group Work summary 
==================


Surface emissivity group (Steve)
================================

* current status in arts
  - general solution for full stokes hemispherical integration 
    including separate handling of emission and reflection
  - no physics for any actual surfaces
* what is available
  - FASTEM2 in RTTOV7 - calculates v,h given wind speed and skin temp
    for ocean.
  - land model is purely empirical, atlases(C. Pringent, t. Hewison)
  - FASTEM3 in RTTOV8 - added a correction to emission term for 
    azimuthal variations for all azimuthal variations (Poe.G via
    Weng.F). 
  - f.weng - NOAA snow + sea ice emissivity model
  - IOMASA snow + sea ice emissivity model
  - c.matzler - snow emissivity - complicated

* recommendations
  - high priority
    - incorporate FASTEM3 from RTTOV8 ocean only.
    - this is easy-  land code less valuable
    - adapt arts input interface to accept wind vector and skin temp.
    - retain direct input of pre-calculated emissivity.  
    - add no other surface variables yet
  - medium priority
    - consider replacing FASTEM3 with full GO model exploiting 
      general solution already in ARTS
    - info from AAPP or other sources to pre-calculate emissivity
  - low priority
    - when schemes for land, ice, snow emissivity mature and simplify 
       - incorporate in arts
    - also take care of different definitions of stokes vector 
       - look at windsat data


Research ideas (Cory)
=====================

* writing papers looking at science issues
* looking at cloud micro physics 
* real ice water content field
* find a cloud field scenario 
* comparison of RT models - MC and DOIT
* discussed Claas' problem at 500 GHz
 - cory will do it for MC
 - problem with scattering integral for 1D DOIT method for higher stokes component.
SB - something to look into in at Bremen
SB - any ideas for the 3D scenario?
CD - output from RT study, TRMM (last slide of cory's presentation)
SB - good thing to look at RAL scenario explained in UTLS study


RTTOV-ARTS comparison (Una)
===========================

* clear sky results - quite good agreement
* rttovscatt doesn't simulate lowest TB's
*  ARTS vs obs good(re = 100 um)
* micro physics - step back from RT - agree on suitable size distr  param
   - set distr. by max crystal size rather than mean crystal size
* surface emissivity
* 3 way model intercomparison
 - to involve al gasievsky's model   


General RTM (Franz)
===================

* discussed parameterization of RT models


PyARTS group (Cory)
===================

* short presentation of what PyARTS can do
* grid optimization - patrick's numerical method was discussed
  - one has to derive the optimized grid from a set of different scenarios
  - scattering integral calculation- improvement using gauss-legendre method
SB - isn't that difficult?
CD - if the function can be represented by a polynomial, you can get accu
rate results
SB - if the phase matrix is peaked, one has to be careful
CD - trapezoidal integration is not sufficient


AMSU working group (Nathalie)
=============================

* ozone line problem
 - influence?
 - 10 years ago, metoffice did some calculation and found negligible
    differences
 - about 0.3 K difference was found during some recent calculation at Bremen
 - some calculations will be done again including stratospheric and
   excluding and then comparing.
AI - send the fascod profiles to Steve to perform similar calculation
* scan angle dependence on AMSU-B
 - amsu-a biases are not symmetric and can be found from NCEP
 - amsu-b biases are symmetric
 - steve can also give info on values regarding biases
*NOAA 15 and 16 BT diff
 - a 1K difference was found in the calculation at Bremen
AI - to compare NOAA 15 and NOAA 17
* side bands
  - rectangular pass band for ARTS and RTTOVB
  - diff are negligible with Gaussian passbands
* ARTS - RTTOV comparison
  - differences are larger than the mean difference at some places
AI - checks whether the profiles are within RTTOV limits
AI - check temp profiles - strong inversion
AI - extract those profiles and perform with a fine grid using ARTS
* AMSU -B channel 18


AUG group (Patrick)
===================

* overview of documentation structure
* control file examples - AI to remove old files and update them 
  with working new ones
* details by command line help
* code documented by doxygen and code comments
* no link between arts-xml-data and arts1-1
  - arts-xml-data only for internal usage
* went through the AUG
  - no obsolete text and FIXME
* doxygen doc- highly appreciated
  - command line description of WSMs will be put into doxygen


Future plans
============

SE - surface data from some low-frequency instruments
SB - lower frequencies were not the priority
   - in the framework of the new instruments, sub-mm frequency are preferred
SE - but one can test the model for low frequencies
PE - single scattering properties - IR?
   - is the database by Bonn going to be general? to be useful for IR.
CD - it is intended to be more general for any RT calculation
SB - use mailing lists with suggestions
   - Adrian for ex. can communicate about his single scattering code.
CM - working group summaries, presentations on the web page
Everyone agreed
SB - if somebody need papers that were discussed, can be obtained. 
CM - Dietrich's paper on intercomparison on JPL and HITRAN.

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