CCMVAL Radiation code intercomparison
	A Survey of Radiation Schemes Used in Climate Models
	    Piers Forster, University of Leeds, based on that started by  
            Qiang Fu, University of Washington

18 June 2007. Piers Forster (piers@env.leeds.ac.uk)
www.env.leeds.ac.uk/~piers/ccmvalrad.shtml

Please answer as many questions as you can with as much detail as possible

I.Description of current radiation model used in the CCM in your centre
  (please give the references wherever appropriate)

 1.Parameterization of Gaseous Absorption

   (a) Data

       Year of HITRAN (or other line parameter archive; if different HITRAN
       data were used for different gases, you might specify the data
       sources for different gases separately):

       Data of O3 absorption cross sections in the visible and UV:

       Other data used if any (e.g., NO2, O2*O2, O2*N2):

   (b) Shortwave radiation

       Number of bands and band intervals:

       Methodology (e.g., correlated k-distribution method or k-distribution
       along with certain scaling and others):

       Treatment of gaseous overlap:

       The total number of K values if the correlated k-distribution method
       or the k-distribution is used:

       H2O (e.g., spectral range considered, total number of k-values and
       any other comments):

       O3 (see above):

       CO2 (see above):

       O2 (see above):

       H2O continuum (see above):

       other minor gases if any:

   (c) Longwave radiation

       Number of bands and band intervals:

       Methodology (e.g., correlated k-distribution method or k-distribution
       along with certain scaling and others):

       Treatment of gaseous overlap:

       The total number of K values:

       H2O (e.g., spectral range considered, total number of k-values and
       any other comments):

       CO2 (see above):

       O3 (see above):

       N2O (see above):

       CH4 (see above):

       CFCs (see aobve):

       H2O continuum (see above):

       others:

 2.Parameterization of Single-Scattering Properties

   (a) Water clouds

       Refractive index (references):

       The way in which cloud optical properties are averaged cross bands:

       Formulation of parameterization:

       Parameterization of effective radius:

       Other comments:

   (b) Ice clouds

       Refractive index:

       Ice particle shapes assumed and definition of the effective size:

       Light scattering program used to derive the single-scattering properties
       of non-spherical ice particles:

       The way in which cloud optical properties are averaged cross bands:

       Formulation of parameterizations:

       Parameterization of ice particle effective sizes:

       Other comments:

   (c) Aerosols

       Types and size distributions and whether they are determined
       interactively or prescribed:

       How the optical properties of hygroscopic aerosols depends on humidity:

       Other comments:

   (d) Rayleigh scattering

       how the spectral dependence is considered:

       Other comments:

 3.Parameterization of Radiative Transfer

   (a) Shortwave

       Transfer scheme (e.g., delta-Eddington scheme):

       Cloud overlap treatment:

       Cloud horizontal inhomogeneity treatment (including whether convective
       clouds, or any other types of clouds, are treated separately):

       Other comments

   (b) Longwave

       Transfer scheme:

       Cloud overlap treatment:

       Cloud horizontal inhomogeneity treatment (including whether convective
       clouds, or any other types of clouds, are treated separately):

       Consideration of scattering processes:

       Other comments:

 4. Surface emission and albedo

       Types

       Spectral dependences


II  Implimentation of your radiation scheme within the CCM

 1. How often the radiation scheme is usually called in your centre's climate
    simulation (e.g., a model time-step of 30 minutes with radiation called
    every three hours for each, or several grid points).  Can this be an issue
    in the climate simulation or numerical weather forecast?

 2. Typical vertical resolution and top level. Are there any absorbers (O3,O2..) above your model top? Are inputs specified on LEVELS (where fluxes are calculated) or LAYERS (where heating rates are calculated). Does the model use a pressure or height grid?

 3. What equations/tables  are used to get solar position and day-length?

 4. Does your code employ a factor to estimate effective path length?

 4. How are heating rates calculated from fluxes - (e.g. constants used)

 5. What is the extra terresterial solar spectrum/solar constant used and how does this vary with season?

 5a. What is the total extra-terresterial solar irradiance used typically in each band of the SW scheme?

 5b. What is the total extra-terresterial solar irradiance used  in each band of the SW scheme for the iintercomparison exercise?

 6. Does your radiation scheme calulate photolysis rates? If not what is the scheme that does?

 7. Does your scheme allow for non-LTE effects above the stratopause in either solar (including losses due to airglows) or infrared parts of the spectrum? if so please fill out IIa.

 8. Does your scheme allow for vertical/horizontal gradients in well mixed greenhouse gases?

 9.  How do you check you scheme's accuracy?

 10. Do you make any modifucations to your schmeme (eg. alter cloud) to retain global energy balance in the model?

 11. Are there any differences between schemes used in stratospheric and tropospheric versions of the model?

IIa Non-LTE treatment

please note that energy losses due to airglows following absorption by O3 and O2 are considered Non-LTE effects here

1. What spectral intervals and absorbers are included in calculations solar heating and infrared cooling above the stratopause?

2. In which spectral intervals and for which absorbers are non-LTE effects taken into account?

3. Above which height level are non-LTE effects included for each spectral band and absorber from IIa.2, specify the merging region if applicable?

4. What approaches are used for non-LTE treatment for each spectral band and absorber from IIa.2


III. What are the recent updates to your radiation scheme and how do the differences affect climate simulations?

IV. What are the main modifications you plan to make to improve the current
    radiation scheme in the near future?

V. What are the major challenges, you think, in the parameterization of
    radiative processes for CCMs/GCMs?

VI.  Are you happy with the CPU time taken by the radiation calculations in the
    climate simulations?  If not, what is the ideal CPU as compared to current
    one (e.g., a factor of 3 times faster)?  How can we approach it?

VII. Other issues that require attention

VIII. Whom are the resposible individuals and their contact details?