A high-resolution urban CO 2 transport model with anthropogenic and biogenic fluxes

We develop PALM-CO 2 , a high-resolution urban carbon dioxide transport model with anthropogenic and biogenic carbon emissions. The PALM-CO 2 model is implemented within the open-source urban-flow large-eddy simulation (LES) model PALM. Anthropogenic CO 2 emissions are prescribed using an external emission inventory, while biogenic CO 2 fluxes are computed online using the Vegetation Photosynthesis and Respiration Model (VPRM). In addition, custom output modules are developed to diagnose carbon fluxes. PALM-CO 2 is validated through a case study in London, comprising an 8 by 8 km 2 domain covering the borough of Camden at a resolution of 10 m. Simulations are driven by reanalysis meteorological forcing and background CO 2 concentrations, while the hourly anthropogenic emissions at 10 m resolution are explicitly derived in this study. Validation against eddy-covariance flux measurements within the study region confirms that the model captures the diurnal variation of turbulent transport and anthropogenic emissions. The biogenic flux module is evaluated independently using observed monthly diurnal profiles of biogenic CO 2 fluxes from a deciduous forest site in the Czech Republic. The comparison shows that the model captures realistic seasonal and diurnal variations in ecosystem carbon exchange. Analysis of the London simulations reveals strong spatial heterogeneity in near-surface CO 2 concentrations arising from the interaction of building-induced turbulence, diurnal boundary-layer evolution, and emission patterns. PALM-CO 2 provides a high-resolution framework for investigating CO 2 transport processes in complex urban and vegetated environments, providing improved quantification of urban emission sources.