Continuous Intercomparison of Radiation Codes (CIRC)

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The Continual Intercomparison of Radiation Codes
(CIRC) Report to IRC, July 2009
Lazaros Oreopoulos1 and Eli Mlawer2
1NASA-GSFC, Greenbelt, MD, USA 2AER, Lexington,
MA, USA
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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 DOEs 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

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LW QC LBLRTM spectral comparisons with AERI
radiance difference
errors lt 1 Wm-2
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CIRC website
http//www.circ-project.org
http//circ.gsfc.nasa.gov
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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

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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

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Phase I initial results, flux errors
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Phase I CO2 forcing experiment
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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