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Traceability for atmospheric total column ozone
ATMOZ
A Joint Research Project within the European
Metrology Research Programme (EMRP)
Julian Gröbner & JRP consortium
Physikalisch-Meteorologisches Observatorium Davos, World
Radiation Center
The EMRP is jointly funded by the EMRP
participating countries within EURAMET and the
European Union
The European Metrology Research Programme (EMRP)
The EMRP
• supports the collaboration of European metrology institutes, industrial organisations
and academia through Joint Research Projects (JRPs).
• is jointly funded by the EMRP participating countries and the European Union with a
total budget of 400 M€.
The European Metrology Research Programme (EMRP)
The EMRP
• supports the collaboration of European metrology institutes, industrial organisations
and academia through Joint Research Projects (JRPs).
• is jointly funded by the EMRP participating countries and the European Union with a
total budget of 400 M€.
Provides access to know-how and
infrastructure from the metrology community
PMOD/WRC
Solar radiometry
(SRS) since 1971
Infrared radiometry
(IRS) since 2004
UV radiometry
(WCC-UV)
since 2005
Optical depth
WORCC since 1996
World Radiation Center
The Physikalisch-Meteorologisches Observatorium
Davos and World Radiation Center (PMOD/WRC)
The 2 Worlds of PMOD/WRC
The PMOD/WRC is designated Institute of METAS for solar irradiance:
Signatory of the CIPM MRA
Implementation of a Quality System according to ISO 17025
Holder of 2 CMC's for solar irradiance and 4 CMC's for solar UV
The PMOD/WRC is designated World Radiation Center by the WMO:
operates instruments representing radiation quantities accepted as world reference standards by the WMO
Calibrates meteorological radiation instruments
Provides traceable measurements to SI
EMRP-ENV59 “ATMOZ”
o Provide traceability of total column ozone to 1%,
o Radiometric characterisation of Dobson and Brewer
spectrophotometers,
o Development of array-based solar UV
spectroradiometers,
o Improved and consistent ozone absorption x-sections,
o Comprehensive uncertainty budget incorporating
instrumental and atmospheric uncertainties
o Project Coordination: PMOD/WRC,
Julian Gröbner
o Duration: 10/2014 – 9/2017
o Total Budget: 2.5 M€
o 9 Partners NMI-DI, Industry, Universities
Present
A traceable and harmonized Global Total Column Ozone Network
Stakeholders and Collaborators
What are the main challenges?
DOBSON
1) Seasonal total ozone differences between
Brewer and Dobson in Arosa, Switzerland.
10 DU
3) Eventual phase-out of Dobson (Brewer) requires
introduction of new total ozone measuring instruments
Brewer, 1973
A comprehensive uncertainty assessment of total column ozone measurements
from Dobson and Brewer spectrophotometers has not been made so far.
Scarnato et al., 2009 Redondas et al., 2014
2) Dobson spectroscopy (slit functions and wavelength
dispersion) are only known for Dobson #083
Tzortziou et al.
Data Scaling method Uncertainty, %
Statistical Systematic Total , %
Hearn, 1961 (253 nm) Absolute , pure ozone 1.05 - 2.1
Anderson et al. 1992*** Absolute , pure ozone - 0.5 0.7
Anderson et al. 1993*** Using Anderson et al. 1992 - 1.3 < 2
El Helou et al. 2005*** Absolute , pure ozone <0.82
Petersen et al. 2012*** Using BMD and BP 0.085 ~2 > 2.1
Axson et al. 2011*** Using Orphal 2003 4 - 30
BP, 1980 – 1985 Using Hearn 1 2.1 >2.1
BMD, 1992 – 1998 Absolute , pure ozone 0.9 –2.2
1.3 (Hartley) 1.3 - 2.5 (Huggins) 1.5-4 (350-420 nm) 1.5 (420-830 nm)
2 – 3 2 – 4 2 – 6 2 – 3
Burrows et al. 1999 Absolute, titration Lamp drift < 2 2.6 2.6 -4.6
Voigt et al. 2001 Integrated Burrows et al. > 2.6 – 4.6 3 – 6
Bogumil et al. 2003 Using BP <1.1 > 2.1 3.1*
Gorshelev/Serdyuchenko 2014 Absolute, pure ozone 0.8-1.8 % 1.4 – 3.2 % 2 – 6**
*excluding regions with s<10-23 cm2/molecule (365 – 410 nm and longer than 950 nm) and 305-320 nm **excluding regions near 380 nm and longer than 800 nm ***discrete wavelengths
Overview on uncertainties in ozone absorption x-sections
• Different sources can provide slightly different versions (e.g. Bass-Paur modified for ground and satellite retrievals
• Single wavelength measurements can be very helpful because of high accuracy
• Reported uncertainties can be underestimated or incomplete
Courtesy Mark Weber
How to address these issues?
1) Radiometric characterisation of current reference ozone spectroradiometers
• Dobson 083 – World standard (NOAA)
• Dobson 064 / 074 – Regional Standards RA VI (DWD, CHMI)
• Brewer #18x – RBCC-E reference Triad instrument (AEMET)
2) Development and characterisation of array spectroradiometers
• Development of a UV optimised spectroradiometer (UV-PSR) PMOD
• Characterisation and operation of a Pandora system (ULL)
• Characterisation and operation of a Phaeton system (LAP)
3) Comprehensive uncertainty budget for total column ozone
• Measurement and uncertainty evaluation of ozone x-sections (Univ. Bremen)
• Uncertainty budgets for Brewer/Dobson & DOAS algorithms (All)
Measurement of line-spread functions at the tuneable
laser facility at PTB
YIB=C Ymeas
The stray-light corrected signal YIB can be retrieved from the measurements by applying a stray-
light correction matrix C to the measured signal, following the method of Zong, 2006.
Measurement of line-spread functions at the tuneable
laser facility at PTB
YIB=C Ymeas
The stray-light corrected signal YIB can be retrieved from the measurements by applying a stray-
light correction matrix C to the measured signal, following the method of Zong, 2006.
UV-PSR - Dedicated to direct solar irradiance measurements
• Radiometric resolution 0.3 nm
• Wavelength range 300-390 nm & 380-470 nm
• 7 x oversampling: 2048 pixel – 7 pixel / FWHM
• Entrance optic Flat field better than 1%
• 2048 pixel UV optimised CMOS or CCD Detector
• 18 bit ADC – 262 kCounts, Signal to Noise >104
• Stray light optimised design with zero-order light-trap (< 10-5)
PSR
linear
spline
Interpolation:
Major Campaigns within ATMOZ
• Characterisation of spectroradiometers at PTB: • Line-spread functions using tunable laser source (in & out-range stray-light)
• Linearity
• Dispersion – Wavelength /pixel relation
• Absolute irradiance calibration
• Field Campaign at Izaña, September 2016: • Reference Brewer Triad for total column ozone
• Reference QASUME for direct UV irradiance spectra
• Fourier Transform Spectroradiometer (FTS) in the UV
• Array spectroradiometers: Pandora, Phaeton, UV-PSR,...
• RBCC-E Campaign in 2017 • In collaboration with COST ES1207 - EUBREWNET
Benefits to Pandonia
• Reference Pandora from Izaña gets characterised in ATMOZ
• Validation of O3 retrievals & elaboration of uncertainty budget
• Comparisons and evaluation with respect to different instruments
• Activities financed by EMRP
• Pandonia can become collaborator to the JRP and participate to
JRP activities (Meetings, campaigns, workshops)
http://projects.pmodwrc.ch/atmoz/
Project Web-site