ICOS Science Conference 2022: Day 3, Session 17

1. One Year of Aircraft Vertical
Profile Measurements of
CO2, CH4 and CO in Tropical
East Africa
Kathryn McKain
Colm Sweeney, Arlyn Andrews, Andy Jacobson,
Tim Newberger, Sonja Wolter, Phil Handley
University of Colorado and NOAA Global
Monitoring Laboratory, Boulder, Colorado, USA
ICOS Science Conference
15 September 2022

2. Global Greenhouse Gas Reference Network
Discontinued
• Importance of Africa in global carbon cycle
• Currently only 4% of global fossil fuel emissions, but very
large projected increases in population and per capita GDP
• ~50% of global biomass burning carbon emissions
• ~25% of interannual variability in global carbon balance
• Carbon-climate feedbacks
• Longstanding observational gap
2
IAGOS-Core GHG, Sep 2018 - Apr 2021
Figure from C. Gerbig
ICOS Atmosphere stations
Motivation for establishing aircraft measurements in tropical Africa

3. 2019
Average land fluxes from north tropical
Africa from models assimilating OCO-2 and
in-situ data (OCO-2 v9 MIP)
Motivation for establishing aircraft measurements in tropical Africa
• Significant recent findings based on satellite retrievals of CO2 and CH4
The 2015–2019 annual means minus the 2010–2014 annual
means of a posteriori tropical CH4 emissions (Tg/year)
2022
3

4. • Kampala Executive Aviation (KEA) aircraft charter company
• Modified and instrumented Cessna 208B Grand Caravan
• Measurement system installed and operated by KEA personnel
• Measurement system designed to be robust, low-maintenance,
easy to operate, and quick to load on and off the aircraft
Aircraft and Measurement System in Uganda
Picarro measurement system for CO2, CH4, CO
Sample Inlet
KEA Cessna Grand Caravan
4

5. • Measurement system installed and operated entirely by KEA personnel due to COVID travel restrictions
in 2020-2021
• National internet outage during national elections in early 2021
• Lengthy permitting process at beginning of each calendar year resulted in data gaps during dry season
• Military control of airspace
• Surging aviation fuel prices
Challenges to Program Execution and Continuity
Picarro measurement system for CO2, CH4, CO
Sample Inlet
KEA Cessna Grand Caravan
5

6. 6
Flight Paths and Geographical Coverage

7. • 21 flights
• 1-year+
• Gaps after New Year
related to permitting
7
Time Coverage

8. Comparison of northern Uganda free-troposphere and nearest GGGRN surface observations
IZO
ASC
SEY
8

9. Profile 1
(South)
Profile 2
Profile 3
Profile 4
(North)
CO2 CO
CH4
Characterized by large enhancements,
variability, vertical structure in all 3 gases,
throughout the year, and across latitudes
Outside of Kampala, landscape appears
rural with a moderate number of satellite-
detected fires in the vicinity.
9
Example Vertical Profiles
2020-12-30

10. 15
45
CO:CO2 and CH4:CO2 ratios are higher near urban region.
10
Tracer-Tracer Relationships
2020-12-30

11. 11
Geographic and seasonal patterns impacting observations
• Wet/dry seasonality
• Unimodal wet season in northern Uganda and bimodal wet season in southern Uganda
• Biomass burning
• November – March
• Higher in northern Uganda
East Africa is a mosaic of different rainfall regimes
Herrmann & Mohr, 2011
Ramo et al., 2021
Burned area
Seasonal biomass burning

12. 12
Seasonality in Vertical Gradients
Vertical gradient =
Median at alt 1 -3 km –
20%ile at alt > 5 km

13. 13
Summary
• 200+ aircraft vertical profiles of CO2, CH4, CO covering
1-year+
• Large-scale enhancements
• Wet/dry seasonality
• Dataset ready for sharing and distribution
• Applications:
• Direct evaluation of satellite retrievals, via:
• Coincident observations
• CTMs assimilating satellite obs
• Evaluation of biomass burning models, especially
importance of small fires
• Evaluation of emission inventories for unique mix
of sources in Africa
Thank you! Questions?
contact: Kathryn.mckain@noaa.gov
Image credit: Lauren Dauphin/NASA Earth Observatory using VIIRS data from NASA
EOSDIS LANCE, GIBS/Worldview, and the Suomi National Polar-orbiting Partnership

14. 14

15. 15
Synoptic climatology for Eastern Africa
and the western Indian Ocean for four
representative months. The panels show
the seasonal migration of the
Intertropical Convergence Zone (solid
black line), the monthly precipitation
(shaded green, contours at 50 mm
intervals) and the wind fields for the 925
mb level (arrows) with wind speed
proportional to arrow length.
(Zinke et al. 2014, Climate Dynamics)

16. Upwind Influence Region
3-day Lagrangian footprint from HYSPLIT and
GFS 0.25° meteorology showing the upwind
influence region for the Dec 30 flight (flight
track is in red). (Colm Sweeney)
Seasonal variability of the Intertropical Convergence
Zone (ITCZ), Congo air boundary (CAB), tropical
rainbelt, and surface winds over Africa (Dezfuli,
Amin (2017-03-29). "Climate of Western and
Central Equatorial Africa” via Wikipedia) 16