ICOS Science Conference, Session 11

1. TOWARD GREENHOUSE GAS REMOTE
SENSING EVALUATION USING THE AIRCORE
ATMOSPHERIC SAMPLING SYSTEM
Bianca Baier1,2, C. Sweeney2, T. Newberger1,2, J.Higgs2, S. Wolter1,2,
P.Tans2, A. Andrews2, D. Wunch3, L. Cunningham3, C. Arrowsmith3, J.
Hedelius4, P. Wennberg5, H. Parker5, G. Osterman6, H. Chen7, J.J.D.
Hooghiem7, R. Kivi8, P. Heikkinen8, M. Leuenberger9, P. Nyfeler9, C.
Crevoisier10, T. Laemmel11, M. Lopez11, M. Ramonet11 , A. Engel12, T.
Wagenhaeuser12, J. Laube13
1CIRES/UC-Boulder, USA
2NOAA/GML, USA
3U.Toronto, Canada
4Utah State Univ., USA
5Caltech, USA
6NASA/JPL, USA
7U. Groningen, Netherlands
8FMI, Finland
9U. Bern, Switzerland
10LMD, France
11LSCE, France
12GUF, Germany
13 IEK, Germany
1

2. Compatibility between global observing systems
2
NOAA Global Greenhouse Gas Reference Network

3. • Added value for understanding
carbon cycle using spaceborne
observing systems realized if
retrievals are put on same scale
as in situ observational
networks
• AirCore sampling system is a
unique remote sensing
evaluation tool:
§ Samples > 98% of
atmospheric column
§ Calibrated measurements
are traceable to WMO
scales
§ Low operational cost
relative to aircraft
measurements
3
Compatibility between global observing systems
AirCore
NOAA light aircraft ceiling
Karion et al., 2010

4. COCCON
• Over a decade of NOAA/GML AirCore sampling with >100 GHG profiles retrieved
• Several small-scale field campaigns targeted at Total Carbon Column Observing Network (TCCON) sites
• 2018: Remote sensing evaluation within TCCON: co-located AirCore, FTS measurements
• 2018-2019: ICOS RINGO collaboration (Sodankylä, Finland; Traînou, France)
4
2012 2013 2014 2015 2016 2017 2018 2019 2020 2021
Year
390
395
400
405
410
415
Pressure-weightedmeanCO2
,ppmAirCore
NOAA/GMLAirCore Sampling

5. 398 400 402 404 406 408 410 412
AirCore XCO2
(ppm)
398
400
402
404
406
408
410
412
FTSXCO2
(ppm)
1:1 line
FTS = 1.0005 0.0003*(AirCore)
Ratio error: 0.3 ppm CO
2
, WMO surface: 0.1 ppm CO
2
15
20
25
30
35
40
45
50
55
SZA (degrees)
• AirCore-TCCON inter-comparison (2018): U.S. TCCON sites, ~3-5 AirCore flights per site, varied launch times
• AirCore captures >98% of atmospheric mass: greater potential error reduction in retrievals
• TCCON primary reference for satellite evaluation: using AirCore as apriori in retrieval allows for improvements in
retrieval processing, more rigorous comparisons between different remote sensing systems
5
TCCON XCO2 retrieval evaluation usingAirCore
Aircraft ceiling
U.S. TCCON sites:
-Park Falls, WI, USA
-Lamont, OK, USA
-Palmdale, CA, USA

6. • Since 2018, routine, monthly AirCore launches at NOAA are coordinated with A-train constellation in sun-
synchronous orbit with a ~13:00 LT overpass time
• To-date, 12 AirCore flights have been coincident with NASA OCO-2 satellite overpasses
• Two AirCore samplers launched on same balloon string
6
NASAOrbiting Carbon Observatory (OCO-2) XCO2 evaluation usingAirCore
400 402 404 406 408 410 412
AirCore XCO2
, ppm
398
400
402
404
406
408
410
412
414
OCO-2XCO2
,ppm
12-Dec-2017
19-Apr-2018
21-Jun-2018
03-Aug-2018
29-Nov-2018
08-Apr-2019
11-Jul-2019
13-Sep-2019
05-Nov-2019
18-Dec-2019
OCO2 = 1.001 0.001*(AirCore)
1 ppm
1:1 line
High bias, large variability
in OCO-2 XCO2 retrievals
390 400 410
CO2
, ppm
0
100
200
300
400
500
600
700
800
900
Pressure,mb
AirCore CO2
Extrap. AirCore
0.4 0.6 0.8 1
OCO-2 averaging kernel
0
100
200
300
400
500
600
700
800
900
Aircraft ceiling

7. CarbonTracker (CT2019) -AirCore comparisons 2009-2020
7
NOAA CCGG aircraft
network altitude ceiling
• Global models used extensively for satellite retrieval evaluation (e.g. NASA OCO-2 bias corrections)
• CarbonTracker is NOAA’s global CO2 inverse model (Jacobson et al., 2020; http://www.carbontracker.noaa.gov)
that assimilates routine NOAAAircraft Network flask CO2 measurements to ~12-13 km MSL
• AirCore samples to ~30km MSL provide some of only routine GHG measurements in UT/LS for model evaluation
NOAA
routine
aircraft
network
ceiling

8. Remote sensing evaluation at “supersites”
• Tower-based in situ trace gases
• Co-located AirCore profiles
• Continuous EM27SUN
retrievals coincident with A-train
overpasses
• Assess capability for long-term
satellite evaluation with EM27
• Rigorous evaluation of EM27
retrieval biases using AirCore
• AirCore-corrected retrievals used
to evaluate satellite trace gases
• Supplemental observations for
comprehensive evaluation of
retrievals: DLiDAR, radiation
measurements
8
NOAA

9. • Portable, balloon-launched (~30km MSL), autopilot-recovered platform can expand AirCore profiling locations
• High-volume payload capacity is retrievable: allows for high-accuracy payload sensor suite critical for satellite
and retrieval algorithm evaluation (T, P, FPH, aerosols)
• High demand for satellite evaluation efforts, observations in tropics
On the horizon: High-altitudeAirCore Glider Platform
O3sonde
NOAA POPS aerosol
NOAA Frost point hygrometer
9
Potential for profiling at sea

10. Toward an internationalAirCore network
10
• Readiness of ICOS for Necessities of
integrated Global Observations
(RINGO) campaign in Sodankylä,
Finland (2018), Traînou, France (2019)
• First major successful comparisons
between AirCore groups
• Further development of AirCores and
increased sharing of knowledge
• Increased collaboration between
international AirCore groups
• Streamline AirCore profile data
reporting and retrieval algorithms
• Investigate and develop best practices
for AirCore sampling
University of Groningen, Netherlands
Goethe University Frankfurt, Germany
University of Bern, Switzerland
Finnish Met. Institute, Finland
NOAA Global Monitoring Laboratory, USA
University of East Anglia, UK/IEK, Jülich, Germany
Laboratoire de Météorologie Dynamique, Laboratoire des sciences du climat et de l’environnement, France

11. Summary
• As new satellites for trace gas remote sensing are launched, there is continued need
for maintaining compatibility with in situ observing networks to fully realize potential of a
synergistic global observing system
• AirCore is a unique remote sensing evaluation tool with its ability to capture >98% of
atmospheric column and GHG profile traceability to World Meteorological Organization
scales
• NOAAGML recent efforts focus on NASA satellite evaluation using AirCore and
expansion to include evaluation of other satellites using continuous EM27SUN
retrievals:
• expand collaborations with TCCON, COCCON
• extend use of these data for evaluation across satellite communities
• AirCore-Glider system could significantly expand profiling locations on land and at sea,
revolutionizing high-altitude atmospheric sampling
• Current collaborations with RINGO science team is invaluable for furthering
international AirCore network and expanding remote sensing evaluation efforts
NASA ROSES, NASA Jet Propulsion Laboratory
11

12. Supplemental Slides
12

13. OCO-2 vs. AirCore
-110 -105 -100 -95 -90 -85
longitude
36
38
40
42
44
46
48
50
52
latitude
OCO-2
AirCore
Date
Aug 3, 2018
400 402 404 406 408 410 412
AirCore XCO2
, ppm
398
400
402
404
406
408
410
412
414
OCO-2XCO2
,ppm
12-Dec-2017
19-Apr-2018
21-Jun-2018
03-Aug-2018
29-Nov-2018
08-Apr-2019
11-Jul-2019
13-Sep-2019
05-Nov-2019
18-Dec-2019
OCO2 = 1.001*AC 0.001
1 ppm
1:1 line
13

14. EM27/SUN Operation in NE Colorado
• Enclosure system built and tested with EM27 at NOAA using CR1000 data
logger
• First comparisons of EM27 + OCO-2 satellite target mode retrievals + AirCore
via day deployments to prospective NECO tower location
14
12:00 Local time 14:00
410 410.5 411 411.5 412 412.5 413 413.5 414
AirCore XCO2
, ppm
408
409
410
411
412
413
414
EM27XCO2
,ppm
EM27 XCO2
= 0.995*AirCore
EM27 XCO2
1 = 0.25ppm
1:1 line

15. New development: High-altitude AirCore sampling platform
15
• Balloon ascent, autopiloted
descent
• Large payload capacity for
housing multiple sensors (i.e.
FPH, POPS)
• Can return e.g. high-accuracy
sensors typically carried on
weather balloons
• Revolutionize surface to
stratosphere sampling,
enhance weather forecasting
capabilities, and further
satellite retrieval and
algorithm evaluation
Graphic design: Sydnee Masias