1. VOC and NOx under
&
Claude, S. Reimann, C. Plass-Dülmer, F. Rohrer, Matthias Hill, R. Holla, D. Kubistin, S. Solberg
& ACTRIS colleagues
EBAS
Acknowledgement: The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/ ) under grant agreement n° 1

2. ACTRIS-VOC/NOx Activities
ACTRIS - Aerosols, Clouds, and Trace gases Research Infrastructure Network
NA3: Near-surface observations of aerosols, clouds and trace gases
WMO/GAW-VOC/NOx activity
EMEP-VOC/NOx activity
CCL
Data reporting
Quality assurance
Meas. Guidelines
Trend determination
WCC / QA-SAC
ACTRIS-VOC/NOx Activities
Integration/Harmonization
Funding
EUSAAR, EARLINET, CLOUDNET, EMEP and GAW
TFMM VOCs and NOx in ACTRIS, Anja Claude et al.

3. data quality objectives (DQO‘s) for NO & NO2
TFMM VOCs and NOx in ACTRIS, Anja Claude et al.

4. data quality objectives (DQO‘s) for VOCs
TFMM VOCs and NOx in ACTRIS, Anja Claude et al.

5. NA3: Near-surface observations of aerosols, clouds and trace gases
Objective
To maintain and consolidate provision of high quality data for the variables addressed by ACTRIS in order to assure the quality and stability of the network composed of more than 40 ACTRIS labelled stations around Europe
Aims for reactive gases: increase the amount and quality of delivered data by
control exercises through inter-calibration campaigns
side-by side intercomparison for NOx and OVOCs/terpenes
Implementation of «target gases» (VOCs)
implementation of quality assurance tools for data submission
update of the measurement guidelines (also for WMO-GAW)
TFMM VOCs and NOx in ACTRIS, Anja Claude et al.

6. ACTRIS station requirements NOx and VOC
Instruments, instrument set up, suitable inlet lines, filter systems, material, gases, calibration and quality assurances procedures should be designed as recommended in the measurement guidelines for
NOx (ACTRIS Deliverable 4.10, 2014) and
VOCs (ACTRIS Deliverable 4.9, 2014 ), respectively.
This includes, that each site should:
regularly calibrate the instrument with a certified calibration gas  NPL
regularly perform zero gas measurements
 perform monthly measurements of target gases (VOC) and submit the target gas results to EBAS
submit data including uncertainty and precision to EBAS following the protocol, deadlines and use the submission templates
participate at the annual data quality workshop
provide feedback to the open issues in the ACTRIS QC/QA process
TFMM VOCs and NOx in ACTRIS, Anja Claude et al.

7. second revision or approval
VOC data flow
Internal data checks
using ACTRIS-2 tools provided by EMPA
January - March
March 31st
April 30th
2nd half of May
July 31st
automated NILU: data format checker and 1st consistency checks
1. Submission level 0 data including target and zero to NILU:
Label ACTRIS_PRELIM
ACTRIS QA with EMPA-tool by EMPA
Consistency checks
EMEP QA by S. Solberg
Data meeting
Feedback to stations: open issues in the issue tracker
Re-submission
to EBAS
second revision or approval
problems / questions have to be addressed by the data provider;
this will be tracked until a decision maker (EMPA/DWD) closes the issue (successful).
Publication of final data
at EBAS:
«ACTRIS» data
TFMM VOCs and NOx in ACTRIS, Anja Claude et al.

8. VOC (event) data reporting (1st submission by March 31, YY):
---> NEW TEMPLATES provided by NILU for NMHCs level 0 (with target gas/
calibration/zero gas measurements) and level 2
Metadata +
time stamp, VOC-i (nmol/mol), VOC-i_ac, VOC-i_pr, numflag_VOC-i
taken from
TFMM VOCs and NOx in ACTRIS, Anja Claude et al.

9. 1-pentene 2015 (Hohenpeissenberg)
Different detection limit definitions in ACTRIS & EMEP!
1-pentene 2015 (Hohenpeissenberg) DL
1-pentene measured
1-pentene fixed DL
TFMM VOCs and NOx in ACTRIS, Anja Claude et al.

10. VOC QA/QC in ACTRIS with „EMPA tool“ (excel sheet)
3.Ratio plots vs previous years for inspection of outliers
4.Ratio plots vs master station
Currently: manual checks done by the data provider and checked by EMPA visually
automated checks to be developed
5. Step: Annual VOC/NOx QC-Meetings (~2 days)
TFMM VOCs and NOx in ACTRIS, Anja Claude et al.

11. red color: data rejected/outlier
NILU consistency checks of new VOC data (colored) receieved through EBAS-submit compared to existing data in EBAS (grey) by S. Solberg
rank sum test applied
The boxes mark the 25- and 75- quantiles with the median given inside. The whiskers extend to the min and max values or to the 1.5 times P25 and P75 if there is data beyond this range. These outliers are identified with small circles. The right panel presents the data in histograms with the relative frequency given on the y-axis.
These plots are based on the full new and old data sets without any consideration of seasonal variations. The purpose is to look for systematic shifts in absolute levels. A Wilcoxon Rank Sum Test (also called a Mann-Whitney U test) is applied to evaluate this in a statistical manner. This test is based on ranks and not on the data values themselves and is thus less sensitive to peak outliers than e.g. Student T tests See e.g.
The Wilcoxon RS-test tests the hypothesis:
H0: The two sample sets come from the same population, in practice that they come from a population with equal median values
against the alternative hypothesis:
H1: The two sample sets come from populations with differing median values
red color: data rejected/outlier
blue: data ok
grey: historical data
TFMM VOCs and NOx in ACTRIS, Anja Claude et al.

12. Target gas measurements monitor…
…the reproducibility of the instrument, the uncertainty of the measurement (deviation from expected values),the quality of the calibration procedure on a monthly and long-term scale.
TFMM VOCs and NOx in ACTRIS, Anja Claude et al.

13. second revision or approval
NOx data flow
Level 0 data (different formats)
1. Submission
to WCC-NOx cloud
QA process currently under lead by WCC-NOx
File format unification/Data processing/Consistency checks
Feedback to stations: open issues in the issue tracker
Re-submission of Level 0 data to WCC-NOx cloud
Data meeting to discuss problems and progress
(regular?)
Conversion to EBAS file format by WCC-NOx
second revision or approval
problems / questions have to be addressed by the data provider;
this will be tracked until a decision maker (WCC-NOx) closes the issue (successful).
Publication of final data
at EBAS: «ACTRIS» data
TFMM VOCs and NOx in ACTRIS, Anja Claude et al.

14. Molybdenum converters are not recommended!
NOx Data Submission to EBAS
NOx (continuous monitor, 1 hour data):
final 1-hour averaged data (NO, NO2, NO2+, NOy in ppb), including uncertainty, reproducibility, variability (16- and 84-percentile) and data flagging (Level-2 data)
AND
Measurement Guideline NOx-CLD:
required metadata: PMT temperature, reaction cell pressure, ambient ozone concentration +temperature +humidity
useful metadata (CLD): integration time, PMT-voltage, chamber/instrument temperatures, ….
@ EBAS:
Different templates for photolytic and molybdenum converters!
molybdenum converters convert not only NO2, but also other gaseous reactive nitrogen components into NO
Molybdenum converters are not recommended!
TFMM VOCs and NOx in ACTRIS, Anja Claude et al.

15. NOx Correction
F. Rohrer WCC-NOx
1) Dark reaction with ambient O3 in inlet line : NO+O3 (hn = 0)
O3 measurements required
2) H2O quenching:
NO2* + H2O → NO2 + H2O
H2O measurements required (or alternatively adequate drying)
Dark reaction depends on residence time in the inlet line,temperature, and pressure
Example taken from station with a long inlet line  most servere effect. If possible short line with high diameter to reduce the pressure gradient.
@30 ppb O3 5s entspricht 5%
3) Offset correction: nighttime data when O3 > 20 ppb
TFMM VOCs and NOx in ACTRIS, Anja Claude et al.

16. Effect of subtracting night time NO
CLD1
CLD2
CLD3
[ppb]
DWD Met. Observatorium Hohenpeißenberg, April 12 Holla Seite 16

17. Effect of subtracting night time NO
CLD1
CLD2
CLD3
 reduces portion of datapoints with no overlap at all from 44 % to 21.4%
DWD Met. Observatorium Hohenpeißenberg, April 12 Holla Seite 17

18. Reduction of flags in ACTRIS!
NOx
Reduction of flags in ACTRIS!
simplification
Different detection limit definitions in ACTRIS & EMEP!
TFMM VOCs and NOx in ACTRIS, Anja Claude et al.

19. 5 years of ACTRIS/EMEP (GAW) data processed
Open questions/on-going issues
NOx:
Molybdenum converters are not recommended! NOx_pc vs NOx_mc, NO2
Correction of dark reaction with O3 and H2O quenching
VOC & NOx:
Detection limit definition
Correct use of submission templates and correct format of files and correct use of flag lists!
Automatisation of QA/QC process
Data workshop (2015 data) next week in Jülich
NOx side-by-side intercomparison at HPB in October 2016 
VOC side-by-side intercomparison at HPB Summer 2017 
TFMM VOCs and NOx in ACTRIS, Anja Claude et al.

20. ….increase the number of sites!
NO2
VOCs
ACTRIS
EMEP
ACTRIS
EMEP
…and spread and follow the SOPs and QA/QC procedures!
TFMM VOCs and NOx in ACTRIS, Anja Claude et al.

21. Thanks for your attention Photo by Stefan Gilge
TFMM VOCs and NOx in ACTRIS, Anja Claude et al.