Dear GRIPS colleagues,
during the GRIPS workshop in Victoria last year
we decided to perform an off-line radiative transfer code
intercomparison. As a first step it was planned to make
zonal-mean computations for climatological January conditions.
In order to facilitate this intercomparison it is important
to define 'standard` input data which should be used in all
of the radiation transfer computations.
With the Berlin GRIPS workshop coming next month, I would like
to address some questions, to all of the groups who want to participate
in this intercomparison, concerning the requirements of their radiation
codes. It would be useful to discuss these points at the workshop
before the final definition of the input data.
This test of the radiation schemes generally should require:
a) Zonal mean temperature (surface-~80km)
b) Absorber concentrations (surface-~80km):
- ozone
- water vapor (spec. humidity)
- carbon dioxide (CO2)
- other gases (CH4,N2O,CFCs)
- molecular oxygen (O2)
c) Ground albedo
d) Cloud distribution (and cloud liquid water content etc.)
e) Aerosol distributions
In this context the following questions should be clarified:
*
Which water vapor data should be used? To my knowledge there is no
consistent water vapor distribution available, which covers the
entire troposphere, stratosphere, and mesosphere. Is it
reasonable to construct a new water vapor climatology by
combining different datasets, as it was done for ozone? Or is
it sufficient to use a tropospheric climatology extended into
the middle atmosphere in a simple way?
*
Which trace gases are needed: CH4, N2O, CFCs or CO2 and O3 only?
*
Does any radiation code need a detailed aerosol climatology?
*
Is it preferable to start with a clear sky computation and include
clouds at a later stage?
It would be helpful to have a list of the input data actually needed
by the different groups.
2) At which resolution should the data be provided? Do the different
radiation schemes have a flexible vertical resolution, so that all
codes could compute radiative fluxes and heating rates at the same
vertical resolution, say 1 km? Is a latitudinal resolution of 5
degrees
appropriate?
3) Which data format is most practical? Binary GrADS-files, ASCII, or
some other format?
I plan to give a short description of the available observational
datasets
at the workshop so that we can discuss and agree on which to use. The
data
will then be stored on our local workstation in the directory:
/home/GRIPS/raddata
so that they can be transferred by everyone using ftp from our guest
account.
For those who planned to perform the intercomparison for the Berlin
workshop.
Currently you will find datasets in that directory for zonal mean
temperature
(Fleming et al./CIRA) and ozone (FUB) as binary 'GrADS' files and trace
gas
concentrations recommended by the IPCC92 report. You are welcome to use
them.
All other data are still missing (sorry), but will be included after we
have
reached some concensus at the workshop.
Best wishes,
Ulrike Langematz
-----------------------------------------------------Dr. Ulrike Langematz
Institut fuer Meteorologie, Freie Universitaet Berlin
Carl-Heinrich-Becker-Weg 6-10, 12165 Berlin, Germany
Tel: 49 - 30 - 838 711 88, Fax: 49 - 30 - 838 711 28
email: lang@strat27.met.fu-berlin.de
-------------------------------------------------------