Comparative Analysis of Transport Trace Gases in High-Resolution Simulations from ICON-ART and IFS Models

The CATRINE (Carbon Atmospheric Tracer Research to Improve Numerics and Evaluation) project, financed by the European Union, is a ground-breaking initiative aiming at improving the accuracy and dependability of atmospheric tracer transport models. The European Centre for Medium-Range Weather Forecasts (ECMWF) coordinates CATRINE, which brings together an interdisciplinary team of atmospheric scientists, climate researchers, and computational modelers to address significant challenges in emissions monitoring and carbon cycle knowledge. This investigation focuses on high-resolution global simulations of key atmospheric constituents—carbon dioxide (CO₂), methane (CH₄), and carbon monoxide (CO)—using two state-of-the-art numerical frameworks: the ICOsahedral Nonhydrostatic Atmospheric Model with aerosol and reactive trace gas capabilities (ICON-ART) and the Integrated Forecasting System (IFS) to advance our understanding of trace gas transport dynamics and improve numerical modelling techniques.The study implements sophisticated modelling approaches within both frameworks, leveraging ICON-ART's innovative unstructured triangular grid system based on a spherical icosahedron, which facilitates flexible grid refinement and incorporates a height-based terrain-following coordinate system with smooth level vertical coordinate implementation. The ART module, coupled online with ICON, enables detailed simulation of aerosols and trace gases, encompassing their emissions, transport, and removal processes throughout the troposphere and stratosphere. In parallel, the investigation examines the IFS framework, renowned for its global numerical weather prediction capabilities, as well as atmospheric composition/air quality monitoring and prediction as part of the Copernicus Atmosphere Monitoring Service (CAMS).The methodology employs high-resolution global simulations focused on trace gas transport processes, with particular emphasis on the upper troposphere/lower stratosphere (UTLS) region. The validation framework integrates observational data from the DCOTSS (Dynamics and Chemistry of the Summer Stratosphere) flight campaigns to evaluate model performance across various atmospheric phenomena. Also, the analysis examines deep convective overshooting event as characteristic cases where rapid vertical transport significantly modifies UTLS composition, altering mixing ratios of CO₂, CH₄, CO, and other trace species. Statistical analyses quantify model performance in representing these complex transport processes and their effects on atmospheric composition across multiple spatial and temporal scales.The comparative analysis reveals distinct characteristics in how ICON-ART and IFS represent transport processes, particularly during deep convective events and associated overshooting phenomena. These findings contribute substantial methodological advances to atmospheric sciences, with direct implications for improving our understanding of UTLS dynamics, enhancing emissions monitoring capabilities, and supporting more accurate climate change assessments. The research establishes a comprehensive framework for future investigations of atmospheric transport processes, particularly in regions of complex dynamical interactions such as the UTLS region.