The document discusses integrating European TCCON sites into the ICOS Research Infrastructure. TCCON provides complementary and reference data for satellite validation by measuring total column concentrations of greenhouse gases. Currently, European TCCON sites rely on short-term project funding, threatening continued operations. Integrating sites into ICOS could provide long-term funding and support from a proposed Atmospheric Column Thematic Centre. This would help preserve the network while centralizing quality control, data handling, and supporting innovation to improve satellite validation and calibration efforts. However, some open issues around instrumentation, data exchange, and national funding commitments would still need to be addressed.

1. Towards a concept for the integration
of European TCCON sites
into the Research Infrastructure “ICOS”
Thorsten Warneke 1 Mahesh Kumar Sha 2
Justus Notholt 1 Martine De Maziere 2
1 University of Bremen, Germany
2 Royal Belgian Institute for Space Aeronomy, Belgium

2. Atmospheric greenhouse gas measurements 1959 - today
0.01
10
1
0.1
100
Tall towers (~500m)
AirCore
(0-35km)
Aircraft
(0-20km)
since 1959
since 1993
since 1993
since 2011
Stratosphere
Free
troposphere
Boundary
layer
Surface air
sampling
Altitude(km)

3. Atmospheric greenhouse gas measurements 1959 - today
0.01
10
1
0.1
100
Tall towers (~500m)
AirCore
(0-35km) Satellite
(column)
TCCON
(column)
Aircraft
(0-20km)
since 1959
since 1993
since 1993
since 2011
since 2002
since 2004
Stratosphere
Free
troposphere
Boundary
layer
Surface air
sampling
Altitude(km)

4. Scientific value of TCCON
Satellite
(column)
TCCON
(column)
since 2002
since 2004
TCCON provides complementary
information to the in situ measurements.
TCCON data is used to validate models,
e.g. models from the Copernicus
Atmospheric Monitoring Service (CAMS).
TCCON links satellite and in situ
measurements.
TCCON is the reference network for
satellite validation.

5. Linking remote sensing data to the WMO scale
TCCON
FTIR
0 – 30 km
(courtesyofH.Chen)
0 – 13 km
Calibration:
Problem: Atmospheric column
cannot be bottled up

calibration is difficult

link via comparisons with
vertical resolved in situ
measurements

6. Indirect calibration of XCO2 column measurements
Aircraft XCO2 (ppm)
TCCONXCO2(ppm)
(Courtesy of Debra Wunch, Caltech

7. 2002 - 2012
ENVISAT
2009 - ?
GOSAT
2014 - ?
OCO-2
• CO2 and CH4
• “Footprint” 1800 km2
• CO2 and CH4
• “Footprint” 87 km2
• CO2
• “Footprint” ~3 km2
15 years of GHG observations from space
Sentinel 5p
• CH4
• “Footprint” ~50 km2
GHG satellites with high sensitivity at the Earth’s surface
- Provide global information about GHG concentrations
- Significant improvement of retrievals over the last 15
years
- It can be expected that quality of space-borne GHG data
will continue to improve in the future and that satellite data
become more important for carbon cycle research
2017 - ?

8. Tollefson, Nature 2016
Future GHG observations from space
GHG satellite data will become more abundant.
TCCON is needed
- To detect and quantify a spatial bias and/or temporal drift in the satellite retrievals
(Validation)
- To link the satellite retrievals to the in situ standards of the World Meteorological
Organisation (WMO) (Indirect calibration)

9. Total Carbon Column Observing Network (TCCON) 2005

10. Total Carbon Column Observing Network (TCCON) 2016

11. Total Carbon Column Observing Network (TCCON) 2016
TCCON sites operated by European Institutions

12. Current situation of the European TCCON sites
• TCCON is in a transition from a research network to a monitoring network.
Still room for technical publications, but for carbon cycle research the
groups need to diversify.
• Measurements currently funded by short term projects and institutional
funding. A lot of this funding is dedicated to research not to monitoring.
Monitoring aspect is hidden by presenting co-author papers to funding
agencies. Not a long term solution.
• Time consuming retrieval/maintenance work is mainly done by researchers
(senior scientists, postdocs, PhD students). Very little time for doing
research, which is a problem for pursuing a scientific career.
• Engineers cannot be funded from research projects. National laws prohibit
several short term contracts for one person in a row. Therefore continuously
changing employees doing the work.
• Insecurity of funding has led to the imminent closure of 2 stations (Bialystok,
Ascension Is.)

13. Expectations of TCCON PIs from an ICOS integration
• National agencies will commit to long-term funding for the operation of the
sites in addition to the centralised activities at the Thematic Centre.
• The current network of sites will be preserved.
• Centralised activities at the Thematic Centre will make the TCCON data
from European sites more consistent and take work off the TCCON PIs.
• The links to the other components in ICOS will become stronger.
• Increased visiability of TCCON.

14. TCCON-Europe
Exploratory
platforms
(mobile FTS)
ICOS Carbon Portal
Atmospheric Column Thematic
Centre (ACTC)
TCCON database
data users
Thematic Centres
Ocean
Ecosystem
Atmosphere Global TCCON
Measurements
raw data
L2 data
Proposed structure for an ICOS integration
public data
RDdata

15. Ideas for the Atmospheric Column Thematic Centre (ACTC)
A) Centralising QA/QC and offering central retrieval for European sites
Optional central retrieval
• Groups have the choice between own or central retrieval at the ACTC
QA/QC
• Instrument characterisation (maintenance of gas cells, retrieval of ILS)
• Checking quality of subsets (artefacts, S/N, zero level offsets,…)
• Participate in QC committee (tbd)
Link to WMO reference scale and comparability of sites
Combination of travelling standard and vertical resolved in situ measurement
• Maintain a travelling instrument (EM27/SUN) for annual comparisons at all sites
• Aircraft and AirCore measurements (ATC)

16. B) Support and support of innovation
Support
• Knowledge transfer and training (e.g. new operators/scientists)
• Offering data user support
• Develop and distribute useful tools for data providers
• Provide user documentation
Support of innovation
• Make, evaluate and promote new developments (retrieval, instrumental)
• Develop strategies for developing/improving the network
Ideas for the Atmospheric Column Thematic Centre (ACTC)

17. Column data at the Carbon Portal
• Mirror TCCON database or automatically retrieve data from the
TCCON database?
• Rapid delivery data product?
• Link to other European data users (Copernicus/ESA)
• Provide access to user documentation
• Data policy (ICOS CC by 4.0 license, more open than TCCON)

18. Work left for the institutes (national funding needed)
Data collection
- Maintenance of hardware (solar tracker, spectrometer, axillary components)
- Maintenance of observatory automation software
- Checking the operational status of the TCCON observatory (automatic check
of system variables, evaluating lamp measurements for line shape)
In case of problems: a) Identifying the problem remotely or travel to site
b) Finding money for purchasing hardware
c) Travelling to site and fix the problem
Retrieval
- In case of problems during retrieval: Finding the source of the problem and
fixing the problem
Without commitment from national funding agencies for funding the operational
costs and the associated work, no continuous data can be promised.

19. Open issues / Discussion points
Indirect calibration
Combination of a travelling standard (EM27) and AirCore. EM27 visits sites annually.
AirCore frequency needs to be discussed.
AirCore part of ACTC or part of ATC?
Data exchange
Data exchange between Carbon portal and TCCON database needs further discussion.
TCCON suggestion: Data is stored in both places and can be used on the Carbon Portal
for visualisation, .., but if somebody downloads TCCON data it is done from the TCCON
database. What is the suggestion from the CP?
How does the Carbon data portal link with the Copernicus Climate data store?
Data policy
TCCON data policy is just being re-discussed (input from ICOS needed now, chance of
harmonisation)
Global TCCON QA/QC check
Different suggestions, depends strongly on link of Carbon Portal and TCCON database
Rapid delivery data
How important is this data product for ICOS?

20. Low resolution spectrometers
Too early for an integration in an operational network.
Suggestion: Operation of one EM27 as a transfer standard and maybe other EM27 can
be integrated as exploratory platforms (no operational requirements).
What are the expectations of ICOS EM27 operators?
Approaching funding agencies
How to start the process of approaching national funding agencies? (via ICOS or solely
via TCCON members)
Name
TTC (previously suggested) not a good name, since other column measurements might
be integrated, “TCCON” should not be mixed with other column measurements.
Suggestion: Atmospheric Column Thematic Centre (ACTC)
Open issues / Discussion points

21. Validation requirements for S-5 P CO and CH4
Specific validation requirements have been identified by the S-5p level-2 developers and
the validation team members for their respective products of CO and CH4. This includes
validation of parameters related to the:
spatial validation requirements, e.g.,
global, over land, tropics, urban, polluted conditions, background conditions;
temporal validation requirements, e.g.,
long time series, seasonal cycle;
special validation requirements, e.g.,
artic vortex, natural emission regimes, humid atmospheric conditions, dry atmospheric
conditions, high albedo conditions and low albedo conditions;
specific validation requirements, e.g.,
observation of localized sources to deduce detection limit for small scale variations,
detection of possible spurious variations as a function of the observed line-of-sight,
detection of possible problems under worse than ideal meteorological conditions

22. Processing chainInterferogram
Source
brightness
correction
Laser
sampling
correction
Fourier
Transform
Spectra
Spectral window
averaging
Airmass
correction
In situ
correction
Quality control
Final data
Site specific data
(GPS, time)
Surface pressure,
temperature
House-keeping
file
Retrieval (GFIT)
Profiles of
p, T, H2O
A priori
Spectral
linelist

23. Annual running costs for one TCCON observatory
Power consumption (site dependent - airconditioning): < 5 kW (9000 EUR)
Rent for site: strongly site dependent
Consumables: ~5 kEUR
Travel: strongly site dependent (2x 2 weeks for maitenance)
Personnel (Engineer): half position
Item Lifetime (years) Cost (k EUR)
Laser 5 6
Vacuum pump 10 6
Compressor 4 2.5
Air dryer 5 2
FTIR spectrometer 20 250
Solar tracker 10 70
Computer/IT 5 4
UPS 8 3
Air condition 15 3

24. rainsensor
temperature-
and
humidity sensor
solartracker
Weather station
wind sensor
solar sensor
alarm system
Hardware (outside)

25. Control cabinet
PLC, UPS, Tapes
Electronics,
Compressor,
Vacuumpump
Solartracker
control cabinet
Hardware (inside)

26. Measurement and retrieval

27. Near-infrared spectral region:
• Not many interfering gases  whole
bands can be analysed
• O2 band serves as reference 
systematic errors partially cancel
• Same spectral region as the satellites
with high sensitivity to the surface
Data product: XCO2 = 0,2095
O2
CO2
Intensity
l (mm)
0
2
4
6
8
10
12
14
16
18
20
0 8190
1.2 1.6 2.5
O2
CO2
CH4
H2O
HDO
N2O
CO
HF
0
2
4
6
8
10
12
14
6345 6350 6355 6360 6365 6370 6375
1.569 1.574
l (mm)
Intensity
Measurement and retrieval