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Infrared Radiation Calibration Center of the WRC/PMOD -IRC-

The WRC/PMOD-IRC, also known as the World Infrared Standard Group, is a calibration center that specializes in the calibration of infrared radiation instruments. It is based on the Absolute Sky-Scanner Radiometer (ASR) developed by R. Philipona. The center provides traceable and accurate calibrations to ensure the reliability of longwave radiation measurements.

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Infrared Radiation Calibration Center of the WRC/PMOD -IRC-

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  1. Infrared Radiation Calibration Center of the WRC/PMOD -IRC- Julian Gröbner IPC-X

  2. Official starting date 1 January 2004 Comprises 4 pyrgeometers 2 modified Eppley PIR, 31463, 31464 2 Kipp&Zonen CG4, FT004, 010535 „World Infrared Standard Group“ - WISG - This Standard group is based on the Absolute Sky-Scanner Radiometer (ASR) developed by R. Philipona History IPC-X

  3. Calibration of PIR 31463 and CG4 FT004 is based on IPASRC-II, at Barrow, Alaska in March 2001. History cont. Marty et al., Downward longwave irradiance uncertainty under arctic atmospheres: Measurements and modeling, JGR, 108, doi: 10.1029/2002JD002937, 2003. IPC-X

  4. Instrumentation of IRC Black Body WISG ASR IPC-X

  5. World Infrared Standard Group IPC-X

  6. Based on Philipona et al. formula: C, k1, k2,k3 are unknown coefficients and are retrieved from the calibration. Pyrgeometer Calibration procedure IPC-X

  7. Characterisation in the black body to retrieve k1, k2,k3.C is retrieved but not used as calibration constant. Calibration procedure First Step Pyrgeometer temperature range: +20ºC to -10ºC Black Body temperature range:+15ºC to -30ºC Results from the regression -> C, k1,k2,k3 Thermopile voltage IPC-X

  8. Comparison to the WISG on the measurement platform to determine the pyrgeometer sensitivity C. Calibration procedure Second Step Longwave radiation Difference test pyrgeometer to WISG ±1 W RMS 0.2 W/m2 IPC-X

  9. k1,k2,k3 are retrieved from the black body characterisation Sensitivity C is obtained from comparison to the WISG, and indirectly relative to the ASR. Calibration procedure Conclusion IPC-X

  10. Ratio between ASR-based and Black-Body based Sensitivity C IPC-X

  11. Uncertainty contributions from: ASR ±2 W (Philipona, App. Optics, 2001) WISG ±1 W (variability) Uncertainty of IRC ±2.3 W (1) Typical uncertainty for test pyrgeometer ±2.4 W with a variability during calibration of ±0.5 W Calibration uncertainty-work in progress- IPC-X

  12. For detecting long-term trends, a stable reference over long time periods is fundamental. Absolute levels can be adjusted, if measurements are traceable (for example to the IRC). The quoted uncertainties of the reference should be larger than the potential future level changes. Absolute uncertainty versus stability First important role of the IRC IPC-X

  13. Dissemination of the IRC reference through regional calibration centers Realised in Germany (DWD). Calibrations for individual institutions: Since 2004 more than 40 calibration certificates have been released. Global traceabilityHomogenisation of longwave radiation measurements Second important role of the IRC IPC-X

  14. Maintain the WISG Characterise the absolute sky-scanning radiometer and make routine comparisons with the WISG Build a second ASR - same principle, different design Construct a second Black Body Characterise pyrgeometers in the laboratory and try to understand systematic differences between black-body and ASR based calibrations. Work jointly with the IR-Community. Current and future work at IPC IPC-X

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