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

Abstract

Abstract. Global anthropogenic CO2 sources are dominated by power plants and large industrial facilities. 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 modelling 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 measurement campaign down-wind 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, 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. in the case of Bełchatów). The stochastic nature of turbulent plumes puts fundamental limitations to 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 comparable resolution. A resolution of 1 km or better, however, appears to be necessary to realistically capture turbulent plume structures. At coarser resolution, the plumes disperse too quickly especially in the near field (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 ppm–1.0 ppm 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.

The Lagrangian Atmospheric Radionuclide Transport Model (ARTM) – Sensitivity studies and evaluation using airborne measurements of power plant emissions

“…In such a case, the comparison is challenging because of the turbulent character of the PBL. As pointed out by Brunner et al (2022), observations only provide snap-shots of the real world while simulations provide one realisation of a multitude of stochastic representations of the real world. Simulations with slightly perturbed initial conditions could result in different dispersion patterns of the plume.…”

“…The aircraft observations used for this investigation originate from the Carbon Dioxide and Methane Mission (CoMet 1.0) (Fix et al, 2018;Luther et al, 2019;Fiehn et al, 2020;Gałkowski et al, 2021;Wolff et al, 2021;Krautwurst et al, 2021;Andersen et al, 2022;Brunner et al, 2022). The campaign took place in May and June 2018 and involved three aircraft performing in situ and remote sensing measurements.…”

“…The actual emission rates are unknown. However, Brunner et al (2022) (Farr et al, 2007) Transfer Register (E-PRTR) for the year 2018. The description of the derivation of SC, z 0 , d 0 , and the plume rise as well as the orography data are given in Supplement S4.…”