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Advances in Measurement of Shortwave and Longwave Radiation at Sea

Advances in Measurement of Shortwave and Longwave Radiation at Sea. Chris Fairall Weather and Climate Physics Branch Physical Sciences Division NOAA/ESRL Boulder, Colorado E.F. Bradley CSIRO Canberra, AU R.A. Weller WHOI, USA R. Lukas University Hawaii, USA

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Advances in Measurement of Shortwave and Longwave Radiation at Sea

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  1. Advances in Measurement of Shortwave and Longwave Radiation at Sea Chris Fairall Weather and Climate Physics BranchPhysical Sciences DivisionNOAA/ESRLBoulder, Colorado E.F. Bradley CSIRO Canberra, AU R.A. Weller WHOI, USA R. Lukas University Hawaii, USA Diane Stanitski NOAA Clim.Obs. Div, USA

  2. BIG PICTUREOceanic Near-Surface Flux Observations:A Major EffortGulev et al., Surface energy and CO2 fluxes in the global ocean-atmosphere-ice system. Plenary White Paper, OceanObs2009 • Satellite • J-Ofuro, HOAPS, IFREMER, Goddard • Blended/Hybrid • OAFlux (WHOI), CORE (NCAR), U. Wash. • In situ • SAMOS Archive of R/V (20 vessels) • Ocean Sites Archive flux buoys (20 sites) • Operational TAO/PIRATA/RAMA (200 sites) • VOSCLIM Volunteer vessels with special sensor package Accuracy Requirement? There isn’t one - i.e, there are many. In situ Obs Target – 1 week time scale, residual bias no larger than ±5 W/m^2 IR or Solar Irradiance; Improvement to ±1 W/m^2 very useful

  3. Simple Thermopile-Driven Heat Balance Radiative Flux Sensors Solar Flux – Pyranometer Flux = 0 to 1200 W/m^2 Calibration determines Asol 2nd order: cold sky bias Non-cosine response IR Flux – Pyrgeometer Flux = 200 to 450 W/m^2 Calibration determines AIR and B First term = -100 to 0 Second term = 200 to 450 Third term = -50 to +10 Tcase = case temperature Tdome = dome temperature 2 C difference gives 50 W/m^2

  4. Calibration Methods 1*Factory calibrations 1-2 year Eppley Kipp & Zonen 2*Use special calibration facilities NOAA/GMD Boulder Lab DOE ARM Oklahoma 3*Keep your own secondary standard (see 1 & 2) 4*Field intercomparisons with an ensemble of sensors A Few Ensemble Intercomparisons *Post COARE, Fairall et al. JTECH 1998 *Arctic (SHEBA) Persson et al. JGR 2002 *Comprehensive land-based: Philipona et al, ‘Atmospheric longwave irradiance uncertainty: Pyrgeometers compared to an absolute sky-scanning radiometer, atmospheric emitted radiance interferometer, and radiative transfer model calculations’, JGR 2001 Rooftop radiative flux sensor calibration facility NOAA/ESRL/GMD Boulder, CO

  5. TOGA COARE (1992-1993)Tropical Western Pacific *Set target accuracy *Field intercomparisons Ship, Aircraft, Buoy *Post experiment calibrations Weller, R., F. Bradley, and R. Lukas, 2004: The interface or air-sea flux component of the TOGA Coupled Ocean-Atmosphere Response Experiment and its impact on subsequent air-sea interaction studies. J. Atmos. Oceanic Tech., 21, 223-257. Time series of surface flux component accuracies from 1970’s to today (Colbo and Weller, 2009)

  6. TOGA COARE Surface Sensor Calibration Adjustments Weller et al. 2004 Solar: Sensitivity Coefficient Adjustment (rms 3%) IR: Bias Adjustment (rms 10 W/m^2); Dome Heating Corrections

  7. Joint NOAA/PSD-WHOI Flux Accuracy and Quality Assurance Project for Research Vessels and Flux Reference Buoys

  8. Solar and IR Comparison Stratus 200415 Radiometers on the Ship Main Result – Voltage amplifier issues with one model of Buoy radiometers

  9. Solar Comparison Stratus 20076 solar and 3 IR Radiometers on the Ship • By 2007 have concluded IR fluxes accurate to 3-5 W/m^2 • Solar difficult to compare during cloudy periods • Eppley pyranometers (PSD and WHOI) about 4% lower than K&Z Red – clear sky model; Blue – K&Z; Green - Eppley

  10. Further Analysis of Stratus 2007 Solar DataEppley and K&Z relative calibration Ratio of K&Z to Clear sky and Ratio of Eppley to Clear sky during clear periods Ratio of Eppley to K&Z vs Zenith Angle

  11. Results of the Boulder and Eppley Solar Calibrations • Both PSD Eppleys used on Stratus2007 and WHOI Standard Eppley had lost about 4% sensitivity due to aging • Boulder NOAA/GMD rooftop and K&Z rooftop calibrations are very close. Eppley (laboratory light hemisphere) about 1% lower (possible cold bias effect?) • Conclusion: Modern factory calibrations unbiased to about 1% (3-4 W/m^2) but need to be done yearly. • Measurements to greater accuracy will likely require different technology (sun tracking)

  12. Confirmation from Hawaii Deployment Upper Left: Radiometer comparisons during daylight hours on Days 193 to 194 (I/C day 2). The lower left panel shows an expanded period around local noon.

  13. General Guidelines *Yearly calibrations *Ensemble comparisons useful *Ventilation and/or quartz domes helps *Microvolt accuracy on data logger *Pyranometer – calibration coefficient is critical *Pyrgeometer – dome/case temperature calibration is critical (0.1 C = 3 W/m^2) *Pitch/roll leveling - ???? NUTS and BOLTS STUFF: Bradley, F. & Fairall, C., (2007). A Guide to Making Climate Quality Meteorological and Flux Measurements at Sea. NOAA Technical Memorandum OAR PSD-311, NOAA/ESRL/PSD, Boulder, CO, 108.

  14. BACKUP

  15. Selected References • Bradley, E.F. and C.W. Fairall, 2007: A Guide to Making Climate Quality Meteorological and Flux Measurements at Sea. NOAA Technical Memorandum OAR PSD-311, NOAA/ESRL/PSD, Boulder, CO, 108 pp. • Burns, Sean P. and 14 coauthors, 2000: Comparisons of aircraft, ship, and buoy radiation and SST measurements from TOGA COARE. J. Geophys. Res., 105, 15627-15652. • Colbo, K. and R.A. Weller, 2009: Accuracyof the IMET sensor package in the subtropics. J. Atmos. Oceanic Tech., 26, 1867–1890. • Cronin, M., C. W. Fairall, and M. J. McPhaden, 2006: An assessment of buoy-derived and numerical weather prediction surface heat fluxes in the tropical Pacific. J. Geophys. Res., 111, C06038, doi:10.1029/2005JC003324. • Fairall, C. W., O.P.G. Persson, R. E. Payne, and E. F. Bradley, 1998: A new look at calibration and use of Eppley precision infrared radiometers. J. Atmos. Oceanic Tech., 15, 1230-1243. • Fairall, C.W. and 17 coauthors, 2009: Observations to Quantify Air-Sea Fluxes and Their Role in Climate Variability and Predictability. Community White Paper, OceanObs09, Venice, Italy. [http://www.oceanobs09.net/blog/?p=73 ] • Persson, P. O. G., C. W. Fairall, E. L. Andreas, P. Guest, and D. Perovich, 2002: Measurements near the Atmospheric Surface Flux Group tower at SHEBA : Near surface conditions and surface energy budget. J. Geophys. Res., 107, NO. C10, 8045, doi:10.1029/2000JC000705, 2002. • Philipona et al, 2001: Atmospheric longwave irradiance uncertainty: Pyrgeometers compared to an absolute sky-scanning radiometer, atmospheric emitted radiance interferometer, and radiative transfer model calculations. J. Geophys. Res., 106, 28,129-28,141. • Weller, R.A., E.F. Bradley, and R. Lukas, 2004:  The interface or air-sea flux component of the TOGA Coupled Ocean-Atmosphere Response Experiment and its impact on subsequent air-sea interaction studies.  J. Atmos. Oceanic Tech., 21, 223-257. • Weller, R. A., E. F. Bradley, J. B. Edson, C. W. Fairall, I. Brooks, M. J. Yelland and R. W. Pascal, 2008: Sensors for physical fluxes at the sea surface: energy, heat, water, salt. Ocean Science, 4, 247-263.

  16. Example: Operational NWP Surface Fluxes

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