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CIRC Invitation

An invitation from GRP to participate in the Continual Intercomparison of Radiation Codes (CIRC)

Dear colleagues,
The GEWEX Radiation Panel (GRP) would like to invite you to participate in the Continual Intercomparison of Radiation Codes (CIRC), an effort supported by the Atmospheric Radiation Measurement Program (ARM). CIRC is intended as an evolving and regularly updated permanent reference source primarily for (but not restricted to) GCM-type radiative transfer (RT) code evaluation. For more information, please visit the CIRC website at:,
also mirrored at:
This invitation launches Phase I of CIRC. We provide the community with a free and publicly accessible reference spectral dataset from line-by-line solar and infrared calculations.  Currently, seven atmosphere/surface configurations representing clear and homogeneous/overcast liquid cloud conditions are available. Six of our seven cases are based on observed atmospheric conditions from ARM datasets that were carefully selected to provide consistency between atmospheric input and modeled/observed radiative fluxes. In future phases of CIRC, the dataset will be expanded to include cases with a greater variety of atmospheric/surface conditions.
While you can simply privately download the reference radiative calculations and the input needed to perform your own runs, we strongly urge you to register as formal participants in CIRC and to submit the results of your calculations through our FTP site. As registered CIRC participants, you will receive updates on changes, enhancements, and corrections to our dataset, as well as invitations to participate in CIRC-related workshops and scientific publications. By submitting up to date results and providing us with info on model improvements that come as a result of your participation in CIRC, you'll help set standards for GCM RT model performance.
We are looking forward to your participation and feedback. Please feel free to forward this message to any colleagues you think may be interested.
Lazaros Oreopoulos, leader of CIRC
Chris Kummerow, head of GRP

Contact information

For more information on CIRC please contact Lazaros Oreopoulos.