Impact of atmospheric turbulence on the accuracy of point source emission estimates using satellite imagery

Kurzfassung

Observation-based monitoring of the status of greenhouse gas emissions goals set at the 2015 Paris Climate Summit is critical to provide timely, accurate and precise information on the status of the progress towards these goals. Observations also permit the identification of potential deviations from the adopted policies that could compromise the efforts to reduce the future impact of pollutants on the climate. Current remote sensing capabilities of atmospheric CO2 have demonstrated the ability to estimate emission from its strongest sources, based on imagery of single plumes combined with wind speed estimates. Realistically assessment of the accuracy and precision of the obtained emission estimates is critical, however. Here, we investigate the stochastic impact of daytime atmospheric turbulence on the estimations of CO2 emissions from a lignite coal power plant in Bełchatów, Poland, using a high-resolution (400 m x 400 m x 85 levels) atmospheric model set up in a realistic configuration. We show how the persistent structures in the emitted plumes cause significant uncertainties in retrieved fluxes when applying a commonly-used cross-sectional mass-flux method. on the order of 10 % of the total source strength. These form a significant contribution to the overall uncertainty which remains unavoidable in the presence of atmospheric turbulence. Furthermore, the use of novel temporally-tagged tracers allowed for the decomposition of the plume variability into its constituent parts and explain why spatial scales of variability in plume intensity are far larger than the size of turbulent eddies – a finding that challenges previous assumptions.