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One Year of Aircraft Vertical Profile Measurements of CO2, CH4 and CO in Tropical East Africa

K. McKain1,2, C. Sweeney2, A.R. Jacobson1,2 and A.E. Andrews2

1Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado, Boulder, CO 80309; 303-497-6229, E-mail: kathryn.mckain@noaa.gov
2NOAA Global Monitoring Laboratory (GML), Boulder, CO 80305

Globally, the African continent has the fastest growing population in the world and is projected to have very large increases in emissions of greenhouse gases and air pollution over the next decade, yet it is perhaps the least observed for atmospheric trace gases. Satellite measurements indicate greenhouse gas emission magnitudes and trends that are significantly different than those predicted by inventories and ecosystem models, but little ground-truth data by which to evaluate satellite retrievals for tropical Africa exist. We present one year of aircraft vertical profile measurements of CO2, CH4, and CO recently collected in Uganda in tropical east Africa. Measurements are sensitive to nearby urban emissions and regional-scale terrestrial ecosystem exchange, and reflect strong wet/dry seasonality with very large boundary layer enhancements from biomass burning and wetland emissions. This new dataset will be particularly useful for evaluating satellite retrievals of trace gases, which may be more uncertain in the tropics due to high aerosol and cloud abundances, and global models of biomass burning, which are based on satellite imagery that may be too coarse resolution to capture the numerous small fires that characterize the region. We present preliminary comparisons of the observed boundary layer enhancements and depletions to those predicted for the region by global inverse models, including those assimilating OCO-2 data and a 20-year climatological average of CarbonTracker optimized with in-situ data.

Figure 1

Figure 1. Four vertical profiles of CO2, CH4, and CO from a flight on 30 December, 2020 over Uganda spanning approximately 0-4 °N latitude.