Evaluation of simulated CO₂ power plant plumes from six high-resolution atmospheric transport models

Abstract

Abstract. Power plants and large industrial facilities contribute more than half of global anthropogenic CO2 emissions. Quantifying the emissions of these point sources is therefore one of the main goals of the planned constellation of anthropogenic CO2 monitoring satellites (CO2M) of the European Copernicus program. Atmospheric transport models may be used to study the capabilities of such satellites through observing system simulation experiments and to quantify emissions in an inverse modeling framework. How realistically the CO2 plumes of power plants can be simulated and how strongly the results may depend on model type and resolution, however, is not well known due to a lack of observations available for benchmarking. Here, we use the unique data set of aircraft in situ and remote sensing observations collected during the CoMet (Carbon Dioxide and Methane Mission) measurement campaign downwind of the coal-fired power plants at Bełchatów in Poland and Jänschwalde in Germany in 2018 to evaluate the simulations of six different atmospheric transport models. The models include three large-eddy simulation (LES) models, two mesoscale numerical weather prediction (NWP) models extended for atmospheric tracer transport, and one Lagrangian particle dispersion model (LPDM) and cover a wide range of model resolutions from 200 m to 2 km horizontal grid spacing. At the time of the aircraft measurements between late morning and early afternoon, the simulated plumes were slightly (at Jänschwalde) to highly (at Bełchatów) turbulent, consistent with the observations, and extended over the whole depth of the atmospheric boundary layer (ABL; up to 1800 m a.s.l. (above sea level) in the case of Bełchatów). The stochastic nature of turbulent plumes puts fundamental limitations on a point-by-point comparison between simulations and observations. Therefore, the evaluation focused on statistical properties such as plume amplitude and width as a function of distance from the source. LES and NWP models showed similar performance and sometimes remarkable agreement with the observations when operated at a comparable resolution. The Lagrangian model, which was the only model driven by winds observed from the aircraft, quite accurately captured the location of the plumes but generally underestimated their width. A resolution of 1 km or better appears to be necessary to realistically capture turbulent plume structures. At a coarser resolution, the plumes disperse too quickly, especially in the near-field range (0–8 km from the source), and turbulent structures are increasingly smoothed out. Total vertical columns are easier to simulate accurately than the vertical distribution of CO2, since the latter is critically affected by profiles of vertical stability, especially near the top of the ABL. Cross-sectional flux and integrated mass enhancement methods applied to synthetic CO2M data generated from the model simulations with a random noise of 0.5–1.0 ppm (parts per million) suggest that emissions from a power plant like Bełchatów can be estimated with an accuracy of about 20 % from single overpasses. Estimates of the effective wind speed are a critical input for these methods. Wind speeds in the middle of the ABL appear to be a good approximation for plumes in a well-mixed ABL, as encountered during CoMet.

Separating and Quantifying Facility-Level Methane Emissions with Overlapping Plumes for Spaceborne Methane Monitoring

“…The large eddy simulation (LES), a promising methodology for solving the Navier-Stokes equation, is widely employed to simulate the dispersion in the ABL (Stoll et al, 2020), with results well agreed with observations (Rybchuk et al, 2021;Brunner et al, 2023). The LES run by WRF, a widely adopted atmospheric numerical simulation model framework, is thus a preferred option for spaceborne GHG monitoring (Varon et al, 2018;Cusworth et al, 2019;Brunner et al, 2023).…”

On the theory of the divergence method for quantifying source emissions from satellite observations

“…While advective transport is explicitly resolved by atmospheric transport models, turbulent mixing needs to be parameterized as a sub-grid scale process. The simplified representation of turbulence often represents a major source of uncertainty in atmospheric transport models, especially in terms of vertical mixing in the atmospheric boundary layer (Karion et al, 2019;Brunner et al, 2023;Katharopoulos et al, 2022).…”

“…Here we show a purely synthetic example. We prescribe a vertical emission profile to account for buoyant plume rise, with the majority of the emissions centered around 600 m altitude (Brunner et al, 2019(Brunner et al, , 2023.…”

“…Solving this inverse problem thus typically involves the use of an atmospheric transport model (see, e.g., Houweling et al, 2015;Jacob et al, 2016;Broquet et al, 2018;Ye et al, 2020;Kaminski et al, 2022). However, atmospheric transport simulations at plumeresolving scale, i.e., at a resolution of the order of 1 km or better (Brunner et al, 2023;, are computationally very expensive. It can be expected that the upcoming Copernicus CO 2 Monitoring (CO2M) satellite mission (Janssens-Maenhout et al, 2020;Meijer et al, 2020) will observe several tens of thousands of plumes glob-ally every year for CO 2 alone; that is, 900 strong point sources (> 3.5 Mt/yr) and up to 300 megacities, imaged about 10-50 times annually, e.g., when conditions are cloudfree (Kuhlmann et al, 2021;Wang et al, 2020;Koene et al, 2021).…”

Estimating NOx emissions of stack plumes using a high-resolution atmospheric chemistry model and satellite-derived NO2 columns

“…Large uncertainties exist regarding the ability of atmospheric transport models to describe individual observed plumes (Brunner et al, 2023). Within the CoCO2 project, high resolution models are developed to simulate emissions from individual stacks.…”