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World Optical depth Research and Calibration Center, WORCC

World Optical depth Research and Calibration Center, WORCC. Christoph Wehrli Physikalisch-Meteorologisches Observatorium Dorfstrasse 33, 7260 Davos Dorf, Switzerland. WORCC tasks assigned in 1995: Development of a radiometric reference for Sunphotometry

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World Optical depth Research and Calibration Center, WORCC

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  1. World Optical depth Research and Calibration Center, WORCC Christoph Wehrli Physikalisch-Meteorologisches Observatorium Dorfstrasse 33, 7260 Davos Dorf, Switzerland WORCC tasks assigned in 1995: • Development of a radiometric reference for Sunphotometry • Development of new instrumentation, algorithms and QC/QA • Implementation of a global demonstration network • Summary of global AOD networks

  2. Radiometric Calibrationof WORCC reference standards • Spectral radiance SI scale based on the cryogenic radiometer of PTB (Berlin), transfer via calibrated trap detector • Radiometric response of PFR deter-mined every 6 months by spectral comparator facility. • Reference instrument N01 assumed to be radiometrically stable to <±0.5% Top_of_Atmosphere calibration V0 could be determined in laboratory, if an accurate (<1%) extraterrestrial solar spectrum was available.

  3. Precision Filter Radiometer Network Specifications • Classic sun-pointed filter radiometer, custom built • 4 simultaneous channels at 368, 412, 500 and 862nm • Thermostatic operation, minimized filter exposition • Internal Sun-pointing and pressure sensors for QC • 1 minute sampling rate for hourly/daily statistics • Weekly/monthly data transmission, central processing • Cloud screening algorithms • Data products: AOD, Ångström  (no inversions) • Continuous in-situ and/or (annual) centralized calibration based on high altitude reference, linear interpolation in time

  4. Ny Ålesund Summit Sodankylä Polar Circle Mace Head Jokioinen Bratts Lake Lindenberg Hohenpeissenberg Jungfraujoch Ryori Izaña Waliguan Tamanrasset Mauna Loa Bukit Kototabang Alice Springs Cape Point Marambio GAWPFR: global extent 2004: 9 GAW stations operational, 4 stations pending deployment, 5 additional PFRs operated by FMI, DWD, ETHZ

  5. GAWPFR: temporal extent 6 stations with 4 years at >50% coverage 4 stations with 20% cloud free samples Data available at WDCA up to 2003

  6. GAWPFR: results 2003 Site Annual MLO 0.022 IZN 0.024 JFJ 0.030 ASP 0.049 NAS 0.089 HPB 0.104 MHD 0.116 BLO 0.119 RYO 0.208 Forest fires

  7. AOD Comparison Results • FRC-I Davos, 2 days, fall 2000 10 radiometers at 7, given calibration 2<0.016 • Mauna Loa, 1 year 2000 AERONET – GAWPFR at 4, in-situ cal.U950.007, ()<0.95 • Alice Springs, summer 2000 3+1 radiometers, 2-4, in-situ calibration U95<0.010, (2 instr. >0.02) • Bratt’s Lake, summer 2001 5 radiometers, 4 networks, 5, given cal.2<0.010, U95()<0.25 • WMO goal of AOD uncertainty <0.02 OD is achieved in routine network operations.

  8. Ground based global AOD Networks“are currently mostly un-coordinated” Latitudinal distribution Polar regions: 4 Midlatitude North: 50 Tropics: 26 Midlatitude South: 10 Total 90 Major data gaps Africa, Asia, India, Polar region and Oceans International: AERONET, BSRN, GAWPFR, SKYNET National: Australia, China, Finland, Germany, Japan, Netherlands, Russia, USA(4)

  9. Thank you for your attention

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