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