The Continual Intercomparison of Radiation Codes CIRC Report

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

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

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

CIRC website http: //www. circ-project. org . v o g n a s a . c f s t ht // : p c . g c ir

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: ü e-mail notifications about changes, updates, and corrections to the CIRC dataset. ü 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

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

Phase I initial results, flux errors

Phase I CO 2 forcing experiment

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