This document discusses comparisons of vertical profile measurements of greenhouse gases from an intensive campaign using AirCore samplers at Sodankylä, Finland. It finds that AirCore is a cost-effective tool for stratospheric measurements, with uncertainties of 0.15-0.2 ppm for CO2 and 4-7 ppb for CO. Differences between AirCore profiles were mostly within these uncertainties, though tubing coatings could cause larger CO2 differences. Altitude registration uncertainty was typically around 2 hPa. Future work includes a campaign in Kiruna, Sweden to further improve accuracy of CO measurements and altitude registration.

1. Comparisons of AirCore vertical profiles of greenhouse gases
from an intensive RINGO campaign at Sodankylä, Finland
Huilin Chen1,Joram Hooghiem1, Rebecca Brownlow1, Rigel Kivi2, Pauli Heikkinen2, Markus Leuenberger3, Peter
Nyfeler3, Michel Ramonet4, Morgan Lopez4, Thomas Laemmel4, Andreas Engel5, Thomas Wagenhaeuser5, Emma
Elvidge6, Johannes Laube6, Bianca Baier7,Colm Sweeney7,Francois Danis8, Cyril Crevoisier8
1RUG, 2FMI, 3UBern, 4LSCE, 5GUF, 6UEA, 7NOAA, 8LMD

2. Towards vertical profile measurements within ICOS
ICOS stations
• Atmosphere (towers & mountain or
coastal stations)
• Complementary to ICOS
Atmosphere
• Bridging remote sensing
with the in-situ network
(Tukiainen et al., 2016; Zhou
et al. 2019; Sha et al., 2020)
• Validation of model
simulations
Vertical Profiles
2

3. RINGO (Readiness of ICOS for necessities of
integrated global observations)
Task leader: RUG Participants: GUF, FMI, LSCE, UBern, BIRA, UBremen
The aim is to develop the readiness of in situ vertical profile measurements using AirCore
at ICOS stations & vertical TCCON profile measurements of CH4.
Tasks:
1. High-accuracy in-situ vertical profile measurements
2. Demonstration of vertical profile retrievals of CH4 from the ground-based TCCON
network, at a few stations (e.g., Reunion, Sodankyla and Trainou)
Task 3.1: Exploration to Apply New Technologies for Vertical Profiles
• Not aircraft due to its relatively high operational costs and limited vertical range
• Complimentary to commercial airliner programs (CONTRAIL and IAGOS)
• Also opportunities for stratospheric research
3

4. Stratospheric research requires high-accuracy observations
0 50 100
CO (ppb)
12
13
14
15
Altitude (km)
(a)
AC 04-Sep
AC 05-Sep
AC 06-Sep
AC 07-Sep
LISA 04-Sep
LISA 05-Sep
LISA 06-Sep
402 404 406
CO2 (ppm)
(b)
Altitude(km)
4Hooghiem et al., ACPD, 2020
AirCore obs. of “the mega pyro-cumulonimbus
(pyroCb)” event in British Columbia on Aug. 12 2017
403.5 404.0 404.5 405.0 405.5
CO2 (ppm)
0
25
50
75
100
125
150
CO (ppb)
, OH-corrected, slope: 62.0
, original, slope: 40.0
, OH-corrected, slope: 54.0
, original, slope: 34.0
403.5 404.0 404.5 405.0 405.5
CO2 (ppm)
0
25
50
75
100
125
150
CO (ppb)
04/Sep, OH-corrected, slope: 62.0
04/Sep, original, slope: 40.0
05/Sep, OH-corrected, slope: 54.0
05/Sep, original, slope: 34.0
CO(ppb)
The ratio of ∆CO/ ∆CO2
Engel et al., 2017
AirCore obs. for calculating stratospheric mean ages
• Accurate observations
• Multiple tracers
• Long-term monitoring
What’s required:

5. Validation strategies
• Accuracy of mole fractions
- e.g. CO2:0.1 ppm, CO: 2 ppb on
the WMO scale
• Accuracy of the altitude registration
What needs to be validated?
S 1. AirCore vs. LISA sampler (RUG)
S 2. AirCore vs. AirCore (NOAA Twins)
S 3. Altitude marker (GUF)
Strategies
• Sodankylä 2018
• Trainou 2019
AirCore Campaigns
5

6. RINGO AirCore Comparison Campaigns
Day 1 (Jun
18)
Day 2 (Jun
19)
Day 3
(Jun 20)
Day 4
(Jun 21)
Day 5
(Jun 25)
Day 6
(Jun 26)
Day 7 (Jun
29)
1 RUG/FMI 2 RUG/FMI 3 RUG /FMI 4 LSCE/LMD 6 RUG/FMI 9 GUF 10 LISA
Bern LISA LSCE/LMD NOAA GUF Bern
LSCE/LMD NOAA UEA Bern Bern Bern-light
5 GUF 7 LISA
UEA
Bern
8 Bern
Institutions AirCore Tubing Flights
1. RUG/FMI 40 m 1/4” O.D. + 60 m 1/8” O.D. 4
2. LSCE/LMD 23 m 8 mm O.D. + 46 m 4 mm O.D. 3 (no drying)
3. GUF 20 m 8 mm O.D. + 40 m 4mm O.D. + 40 m 2 mm O.D. 3
4. UBERN 105m 3.4 mm O.D. 7
5. NOAA 100 m 1/8” O.D. x 2 4
6. UEA 8.5 m 1/2” O.D. + 63 or 85 m 1/8” O.D. 2
7. RUG LISA (4 bags) 3
Sum All analyzed on Picarro, primarily G2401 23 AC + 3 LISA
RINGO aims to develop the
readiness of in situ vertical
profile measurements using
AirCore at ICOS stations &
vertical TCCON profile
measurements of CH4.
• 1st campaign Sodankylä 2018
• 2nd campaign Trainou 2019

7. CO2
Mean column differences
• 0 – 0.32 ppm
• UEA tropospheric part on
June 20 ½ in. diameter,
coated
Due to different spatial resolution
• UEA stratospheric part on June
20: Tubing no coating
• GUF on June 25, possibly
smearing during analysis
Larger differences
7

8. Comparison of CO2 profiles
13 CO2 and CO profiles from RUGFMI, NOAA, GUF, LSCELMD
Small variations in the stratosphere
• CO2 above 20 km
• In the CH4 domain 1300 – 1700
ppb (16 – 20 km)
Large variations in the troposphere
• Surface emissions
• Transport
8

9. Uncertainty of CO2 mole fraction observations
In the CH4 domain
1-Sigma: 0.19 ppm
Above 20 km
1-Sigma: 0.15 ppm
Round-Robin cylinder comparison
1-Sigma: 0.10 ppm
VS.
With vs. without drying the air sample
above 16 km
• 0.08 ± 0.18 ppm above 20 km
• 0.15 ± 0.11 ppm between 16 and 20 km
9
Above 20 km
16 – 20 km

10. Uncertainty of CO mole fraction observations
Troposphere 5 – 8 km
1-Sigma: 4 ppb
Stratosphere 13 – 17 km
1-Sigma: 7 ppb
Round-Robin cylinder
comparison
1-Sigma: 2.5 ppb
VS.
10

11. Uncertainties in the altitude registration
11
Flight
dates
AirCore
Comp.
Mean strat. profile diff. (> 13 km) Vertical
shifts
Mean strat. profile diff. after
vertical shifts
CH4 (ppb) CO2 (ppm) CO (ppb) P (hPa) CH4 (ppb) CO2 (ppm) CO (ppb)
20180618 LSCELMD -
RUGFMI
-9.6 -0.02 -7.8 -2 -0.5 0.11 -8
20180619 NOAA009-
RUGFMI
10.4 0.15 -19.7 0 10.4 0.15 -19.7
NOAA010-
RUGFMI
9.0 0.2 -19.1 1 4.4 0.13 -19.4
RUGFMI -
RUGLISA
-31.1 -1.30 27.8 -2 -26.7 -1.27 29.5
20190620 LSCELMD-
RUGFMI
11.5 0.32 12.1 2 3.4 0.22 16.8
UEA -
RUGFMI
10 -2.33 12.1 3 -4.3 -2.53 11.6
20190621 LSCELMD-
NOAA004
37.5 0.37 - 10 -3.9 -0.16 -
GUF-
NOAA004
50.8 0.35 - 13 0.4 -0.28 -
20190625 GUF-RUGFMI -0.3 -0.75 -16.4 -2 7.3 -0.69 -17.1
Median vertical shift: 2 hPa

12. Conclusions & Future work
• AirCore cost-effective tools for stratospheric greenhouse gas and
related tracer measurements
• AirCore mole fraction and altitude registration uncertainties
- Mole faction CO2 0.15 – 0.20 ppm, CO 4 – 7 ppb
- No tubing surface coating can cause large differences (up to ~ 5 ppm) for CO2
- Dry vs. no dry insignificant differences for stratospheric CO2 above 16 km
- Altitude registration uncertainty median ~2 hPa
• Hemera campaign with a large balloon in Kiruna (68N, 21E)
summer 2021 (Whole air sampler, Regular AirCores, Mega-AirCore,
Mega-LISA)
- Improving CO mole fraction accuracy
- Improving altitude registration accuracy