1. The Continual Intercomparison of Radiation Codes (CIRC) Report to IRC, July 2009 Lazaros Oreopoulos 1 and Eli Mlawer 2 1 NASA-GSFC, Greenbelt, MD, USA 2 AER, Lexington, MA, USA

2. Reminder: What is the Continual Intercomparison of Radiation Codes (CIRC)? RT model intercomparison aspiring to become the standard for documenting the performance of RT codes used in Large-Scale Models Working group within GRP and IRC Supported by DOE’s ARM program Goal is to have RT codes of GCMs (incl. IPCC) report performance against CIRC Phase I was launched on June 4, 2008 How CIRC differs from previous intercomparisons: Observation-tested (LW) LBL calculations are used as radiative benchmarks Benchmark results are publicly available Observationally-based input (from an ARM product named BBHRP, mostly) Flexible structure and longer lifespan than previous intercomparisons

3. LW QC: LBLRTM spectral comparisons with AERI radiance difference errors < 1 Wm -2

4. CIRC website http://circ.gsfc.nasa.gov http://www.circ-project.org

5. CIRC modus operandi Input & output (TOA and SFC fluxes at 1 cm -1 ) and instructions on how to run the cases are openly available at the CIRC website Only registered users (considered as formal participants) have privileges such as: e-mail notifications about changes, updates, and corrections to the CIRC dataset. priority to participate in workshops and publications Registered users may have to submit results within predetermined deadlines. Submitted results and intercomparison analysis will be posted on website when finalized Implementation details and performances of participating codes will be documented and evaluated

6. CIRC activities so far Website Phase I launched June 4, 2008 19 requests to register as participants (9 USA, 2 Brazil, 2 France, 2 Russia, 1 Australia, 1 Canada, 1 UK, 1 Finland) Results from 26 RT codes (SW and LW, incl. non-GCM) available for evaluation BAMS article (in press), GEWEX newsletter article, IRS proceedings article, several ARM presentations (oral and poster) Attempt to organize CIRC workshop after Gordon 2009 Efforts to secure additional funding from DOE & NASA

7. Phase I initial results, flux errors

8. Phase I CO2 forcing experiment

9. CIRC future “Pristine” and “cloudless” Phase I sub-cases will soon be released Technical paper on Phase I in preparation Continue efforts to secure funding Encourage submissions from RT codes used for global flux datasets Phase II preparation Perhaps workshop within 2010 Work with community to determine how to use CIRC for efforts like IPCC