Development and evaluation of CO<sub>2</sub> transport in MPAS-A v6.3

Abstract. Chemistry transport models (CTMs) play an important role in understanding fluxes and atmospheric distribution of carbon dioxide (CO2). They have been widely used for modeling CO2 through forward simulations inferring inversion systems. With the increasing availability high-resolution observations, it has become possible to estimate at higher spatial resolution. In this work, we implemented Model Prediction Across Scales – Atmosphere (MPAS-A). The objective is use variable-resolution capability MPAS-A enable a simulation limited region with global model. Treating as inert tracer, (v6.3) processes, including advection, vertical mixing by boundary layer scheme, convective transport. We first evaluated newly model's tracer mass conservation then its accuracy. A 1-year (2014) scale using measurements from 50 near-surface stations 18 Total Carbon Column Observing Network (TCCON) stations. also compared two models: National Oceanic Atmospheric Administration (NOAA) CarbonTracker v2019 (CT2019) European Centre Medium-Range Weather Forecasts (ECMWF) Integrated Forecasting System (IFS). second set (2016–2018) evaluate regional Transport America (ACT-America) aircraft over eastern United States. This CT2019 27 km WRF-Chem simulation. global-scale evaluations show that capable representing temporal variation comparable level accuracy IFS similar horizontal regional-scale observed structures related midlatitude synoptic weather system, warm versus cold sector distinction, free troposphere difference, frontal enhancement. MPAS-A's performance these model WRF-Chem.