Tropospheric Ozone is a GHG

Reference: IPCC (2007)

2

World Calibration Centre WCC-Empa

�Established 1996 for Surface Ozone

� 1997: Carbon Monoxide

� 2000: Methane

� 2007: Collaboration with WCC-N2O

� 2010: Carbon Dioxide

3

Purpose of audits

WCCWorld

CalibrationCentre

CCLStation

Station

Station

Station

• Only one reference in the network

• Traceability chain as short as possible

• Regular audits lead to homogenous data series

RCCRegional

CalibrationCentre Station

Station

WCC-Empa – GAW-CH Conference 2011-01-18

4

CCL WCC Station WCC CCL

TS

Analyzer

PS

LS LS

PS

years years weeks years

LS | WS

Audit scope

Performance Audits and Traceability Chain

christoph.zellweger@empa.ch 5

WCC-Empa audits at GAW sites - Traceability

SRP#2 at NIST SRP#15+23 at Empa TEI 49C-PS / iPS

Travelling Standards

Stations / RCC

WCC-Empa Audits 1996 – 2010 at GAW stations

Bukit Koto Tabang

South Pole

Barrow

Mauna Loa

Alert

08 Pallas-Sodankylä97,03,07

MinamitorishimaAssekrem03,07

Arembepe01

Ushuaia98,03,08

Izaña96,98,00,04,09

Amsterdam IslandCape Grim02,10

Samoa

Ny Ålesund97,01,05

Lauder / Baring Head

Mace Head96,98,02,05,09

Zugspitze 96,97,01,06,(11)

Mt. Waliguan00,04,09

Neumayer Station

Mt Kenya00,02,05,06,08,10

Polar

Circle

40

0

40

80

40

0

40

80

120160 80 40 0 40 80 120 160

Cape Point97,98,02,06,(11)

Jungfraujoch

99,01,04,07,08,(11)

03

99,06 Ryori 05

Hohenpeissenberg 97,06,(11)

Danum Valley

04

08

08

O3/CO/CH4 O3/CO O3 Not yet audited # Year(s) of audit(s)

Cape Verde (11)

Trinidad Head

10

O3/CO/CH4/CO2

7

WCC-Empa – Audit results

0.85 0.90 0.95 1.00 1.05 1.10 1.15

-4-2

02

4Slope / (-)

Inte

rce

pt / (n

mo

l·nm

ol−

1)

API

Dasibi

EG

ML

TEI49

TEI49C

TEI49i

Good [Klausen et al. (2003)], Range 0-100 ppb

Sufficient [Klausen et al. (2003)], Range 0-100 ppb

Intercept vs. slope for ozone audits conducted by WCC-Empabetween 1996 and 2008.

0 20 40 60 80

-50

5

SRP (ppb)

[OC

- S

RP

] (p

pb

)

Sufficient

Good

Good

Sufficient

TEI49C-PS #56546-318Unbiased ozone = OC - 0.38 (ppb) / 0.986

Example of an instrument assessment during an audit

DQO [1]: � 20 ppb: Sufficient: 2.1 ppb + 3%

Good: 1.8 ppb + 2%

> 20 ppb: Sufficient: 1.3 ppb + 7%

Good: 1.4 ppb + 4%

[1] Klausen, J., et al. (2003), Uncertainty and bias of surface ozone measurements at selected Global Atmosphere Watch sites, J. Geophys. Res.-Atmos., 108, 4622, doi:4610.1029/2003JD003710.

8

WCC-Empa – Audit results

Date

Slo

pe

(-)

0.9

00

.95

1.0

01

.05

1.1

0

1998 2000 2002 2004 2006 2008

APIDasibiEGML

TEI49TEI49CTEI49i

Date

Inte

rce

pt (p

pb

)

-20

24

1998 2000 2002 2004 2006 2008

APIDasibiEGML

TEI49TEI49CTEI49i

Slope vs. date of audit for different ozone analyzers

Intercept vs. date of audit for different ozone analyzers

WCC-Empa comparisons 1996 – 2010

Polar

Circle

40

0

40

80

40

0

40

80

120160 80 40 0 40 80 120 160

JMA 05

08

O3/CO/CH4 O3 # Year(s) of comparison(s)O3/CO/CH4/CO2

RCC-BsAs 03,08,10 CSIRO 02,10

NIWA 10

CAWAS 10BIPM 06,(11)

NIST (CCL) 97,99,03,07

NOAA (CCL) (ongoing)CHMI 96,97

10

Surface ozone comparison WMO/GAW Region III WCC-Empa and RCC Buenos Aires (September 2010)

WCC-Empa – GAW-CH Meeting 2010-10-22

0 20 40 60 80

<SRP> (ppb)

Sufficient

Good

Good

Sufficient

TEI49 #49978-285(09/22/10 17:52:30)-(09/23/10 08:52:30)

El Tololo

0 20 40 60 80

<SRP> (ppb)

Sufficient

Good

Good

Sufficient

TEI49 #54501-300(09/22/10 17:52:30)-(09/23/10 06:52:30)

San Lorenzo0 20 40 60 80

-20

-15

-10

-50

51

0

<SRP> (ppb)

[OA

- <

SR

P>

] (p

pb

)

Sufficient

Good

Good

Sufficient

TEI49C-PS #62170-334(09/23/10 19:35:30)-(09/24/10 09:32:30)

Natal

0 20 40 60 80

<SRP> (ppb)

Sufficient

Good

Good

Sufficient

TEI49 #54577-300(09/23/10 11:50:30)-(09/23/10 16:50:36)

La Quiaca

Sufficient

Good

Good

Sufficient

TEI49 #49981-285(09/23/10 19:35:30)-(09/24/10 09:32:30)

Pilar

0 20 40 60 80

-50

5

<SRP> (ppb)

[OA

- <

SR

P>

] (p

pb

)

Sufficient

Good

Good

Sufficient

TEI49 #54947-302(09/22/10 17:52:30)-(09/23/10 06:52:30)

Salto

0 20 40 60 80

-50

5

<SRP> (ppb)

[OA

- <

SR

P>

] (p

pb

)

Sufficient

Good

Good

Sufficient

TEI49 #49983-285(09/23/10 11:50:30)-(09/23/10 16:50:36)

-50

5

[OA

- <

SR

P>

] (p

pb

)

Sufficient

Good

Good

Sufficient

TEI49C-PS #56546-318(09/23/10 19:35:30)-(09/24/10 09:32:30)

San Julian

Ushuaia

11

WCC-Empa – SRP stability

0.990 0.995 1.000 1.005 1.010

-1.0

-0.5

0.0

0.5

1.0

SRP23 vs. SRP15

slope

inte

rce

pt

SRP15

SRP15.old.cellsSRP15.old.electronics

Intercept vs. slope for SRP23 vs. SRP15 comparisons from 2001 - 2011

� Largest change after

electronics upgrade

� Change due to cell and

insulation upgrade not

significant

� Reproducibility of SRP23-

SRP15 comparisons

improved after cell and

insulation upgrade

12

WCC-Empa – SRP stability

Intercept and slope for SRP23 vs. SRP15 comparisons from 2001 - 2011

0.9

95

1.0

00

1.0

05

1.0

10

SRP23 vs. SRP15slo

pe

SRP15SRP15.old.cells

SRP15.old.electronics

2002 2004 2006 2008 2010

-0.4

-0.2

0.0

0.2

0.4

date

inte

rce

pt

2002 2004 2006 2008 2010

13

SRP changes due to recent upgrade

�Small change considering all sources of uncertainty

�All SRPs were upgraded (to be confirmed with NIST)

SRP changes compared to NIST SRP#0

during the upgrade with new cells and improved thermal insulation

Viallon, J., P. Moussay, J. E. Norris, F. R. Guenther, and R. I. Wielgosz (2006), A study of systematic biases and measurement uncertainties in ozone mole fraction measurements with the NIST Standard Reference Photometer, Metrologia, 43(5), 441-450.

14

Open issue: Ozone absorption cross section

�Differences between gas phase titration and SRP ozone

measurements (CCQM Report 28)

�Publication of new absorption cross section planned after finalizing

of experiments (Late 2012, by BIPM group)

�Expected change: +1.5%, i.e. all ozone measurements are currently

underestimated by 1.5%.

� as a consequence, impact on time –series already at WDCs

new data submission, implementation of “versions”

Ozone: future activities / issues

� Up date of Report Nr. 97;sub –SAG RG for Surface Ozone:Ian GalbanyChristoph Zellweger, WCC-EmpaEckhard ScheelBIPMNIST?…..

� DQOs; more strict?

� 3rd Dimension

� NRT

� Trend analysis

DQO [1]: � 20 ppb: Sufficient: 2.1 ppb + 3%

Good: 1.8 ppb + 2%

> 20 ppb: Sufficient: 1.3 ppb + 7%

Good: 1.4 ppb + 4%

Proposed Outline – new report on Measurement guidelines for surface ozone

1 Introduction

2 Rationale and Objectives

3 Data Quality Objectives for O3 Measurements (DQOs of WMO/GAW report 97 outdated; new DQOs subject to discussion)

4 Measurement Setup

Location and siting requirements

Air inlet design (e.g. no sample drying?)

5 Measurement Techniques

UV absorption

interferences

Other techniques (e.g. chemiluminescence, CRDS)

6 Primary ozone reference and traceability

NIST Standard Reference Photometer

cross sections

uncertainties

BIPM key comparisons (including other reference instruments, e.g. KRISS)

Transfer instruments

O3 generators ONLY for quality control checks!

Proposed Outline – new report on Measurement guidelines for surface ozone

7 Quality Assurance and Quality Control

Calibration

Dry/wet air issues

Regular quality control (zero/span) checks

Other checks (flows, pressure, leak checks)

Inlet losses

Measurement protocol

Audit procedures

Particular issues related to airborne and shipborne observations

Evaluation of overall measurement uncertainty

8 Data Management

Data evaluation

Metadata

Ancillary data

Data archiving

Data submission

Data revision (making link to potential future changes of the O3 cross-section)

9 Integration of surface, airborne and ozonesonde observations

Annex Terms and definitions