Broadband detectors Mario Blumthaler

Transcription

1 I N N S B R U C K Broadband detectors Mario Blumthaler Division for Biomedical Physics Innsbruck Medical University, Austria

2 Erythema dosimeters Solar Light YES Scintec / Kipp&Zonen RELATIVE SPECTRAL RESPONSE ERYTHEMA SL No WAVELENGTH [nm]

3

4

5 Objectives for broadband UV measurements: To provide information on variations of erythemal irradiance To provide data for public information and awareness (e.g. UV Index) To provide continuous measurements for climatological studies of erythemal irradiance in addition to spectral instruments To supplement spectral UV measurements (e.g. temporal and spatial interpolation, interpretation of cloud effects) To help in quality control of spectral measurements To contribute to the validation of UV retrievals based on satellite measurements BUT: Broadband instruments are not ideal for trend analysis

6 CALIBRATION OF BROAD-BAND METERS 1 s [nm] d I s M eff ) ( ) ( I CALIBRATION OF BROAD-BAND METERS s 2 s 1 1 s [nm] d I s M eff ) ( ) ( I 1 s [nm] d I s d I s C ) ( ) ( ) ( ) ( 2 1 I Calibration of erythema dosimeters

7 Erythemal effective irradiance / Biometer-signal Comparison UVBiometer - Spectroradiometer Bio 2020 Bio 2021 Bio 2022 Bio 2023 Bio 2024 Bio Solar elevation [degree]

8 Correction of UV-Biometer data UV-Biometer data [rel. Units] mean over 30 min Absolute calibration spectral sensitivity of UV-Biometer ratio to high-resolution solar spectra detector weigthed irradiance [mw/m 2 ]

9 Instrument characterisation - Spectral Response A spectrally dispersed light source is required, preferably in 1-nm steps or smaller (tuneable laser or monochromator) A normalized spectral sensitivity response function is needed for each radiometer

10 Correction of UV-Biometer data UV-Biometer data [rel. Units] mean over 30 min detector weigthed irradiance [mw/m 2 ] erythemally weigthed irradiance [mw/m 2 ] or [UVI] Absolute calibration spectral sensitivity of UV-Biometer ratio to high-resolution solar spectra Model calculation lookup tables dependent on: total atmospheric ozone solar elevation local parameters

11 Conversion matrix: detector weighted erythemally weighted units SOLAR ELEVATION [ ] TOTAL OZONE [DU]

12 WMO-GAW report No.164, 2005: Part 2: Broadband instruments measuring erythemally weighted solar irradiance Lead Author: Co-authors: Contributors: G. Seckmeyer A. Bais, G. Bernhard, M. Blumthaler, C.R. Booth, K. Lantz, R.L. McKenzie P. Disterhoft, A. Webb

13 EC-Publication ISBN , 2006

14 Sensitivity of erythema dosimeters to internal relative humidity REL. SPECTRAL RESPONSE % 22% 35% 51% 70% WAVELENGTH [nm]

15 Short-term stability of erythema dosimeters /09/ /09/16 SL No /09/ SL No SL SL No AFTERNOON / MORNING AFTERNOON / MORNING AFTERNOON / MORNING AFTERNOON / MORNING SL No SL SL SL No. No /09/16 SL No /09/16 SL SL No. No /09/ SL No /09/17 SL SL No. No /09/18 SL No /09/18 SL SL No. No SOLAR ELEVATION SOLAR [ ] ELEVATION [ ] [ ]

16 KALIBRIERFAKTOREN Long-term stability of erythema dosimeters KALIBRIERFAKTOREN BEI SH=35, O 3 =300DU ZEIT [JAHR]

17 International broadband erythema dosimeter intercomparisons 1) 1995, Helsinki, Finland 20 detectors from 16 countries Reference-spectrometer: Bentham DM150 from University Innsbruck WMO-Report No ) 1999, Thessaloniki, Greece 29 detectors from 14 countries Reference-spectrometer: Bentham DMT 300 from University Innsbruck WMO-Report No ) 2006, Davos, Switzerland 34 detectors from 16 countries Reference-spectrometer: QASUME Bentham DM 150 from PMOD and Bentham DMT 300 from University Innsbruck COST-Report

18 Broadband radiometers at the PMOD/WRC-COST intercomparison in Davos, Switzerland, in Instruments from the following companies: 16 Solar Light, 9 YES, 3 Scintec, 4 Kipp & Zonen 1 ELDONET, 1 custom made

19 WMO-STUK-Intercomparison 1995

20 Relative responses 1E+1 1E+0 Es1, Es2, Gr2 1E-1 f 1E-2 VITAL(It1) EKO (It2) 1E-3 EKO (It2) 1E-4 Pl1 Scintec 1E Wavelength (nm)

21 Normalized Ratio (Bentham / broadband). Normalized Ratio (Bentham / broadband). Normalized Ratio (Bentham / broadband). Normalized Ratio (Bentham / broadband). 1.4 SL-501 (1098) Radiometric CF : Weighting function: SRF 1.4 SL-501 (3749) Radiometric CF :1.788 Weighting function: SRF /09/ /09/ /09/ /09/ /09/ /09/ Solar Elevation (deg) Solar Elevation (deg) 1.4 SL-501 (0935) Radiometric CF : 2.11 Weighting function: SRF 1.4 SL-501 (1120) Radiometric CF : Weighting function: SRF /09/ /09/ /09/ /09/ /09/ /09/ Solar Elevation (deg) Solar Elevation (deg)

22

23 Summary broadband detectors are relatively cheap and simple to install (e.g. for networks) BUT: maintenance necessary and regular check of stability of calibration only then uncertainties of <10% possible for comparable results (UV-index) complete characterisation and post-processing necessary