MALTA: A Zonally Averaged Global Atmospheric Transport Model for Long‐Lived Trace Gases.

We present a two‐dimensional, zonally averaged global model of atmospheric transport named MALTA: Model of Averaged in Longitude Transport in the Atmosphere. It aims to be accessible to a broad community of users, with the primary function of quantifying emissions of greenhouse gases and ozone depleting substances. The model transport is derived from meteorological reanalysis data and flux‐gradient experiments using a three‐dimensional transport model. Atmospheric sinks are prescribed loss frequency fields. The zonally averaged model simulates important large‐scale transport features such as the influence on trace gas concentrations of the quasi‐biennial oscillation and variations in inter‐hemispheric transport rates. Stratosphere‐troposphere exchange is comparable to a three‐dimensional model and inter‐hemispheric transport is faster by up to 0.3 years than typical transport times of three‐dimensional models, depending on the metric used. Validation of the model shows that it can estimate emissions of CFC‐11 from an incorrect a priori emissions field well using three‐dimensional (3D) mole fraction fields generated using a different 3D model than which the flux gradient relationships were derived. The model is open source and is expected to be applicable to a wide range of studies requiring a fast, simple model of atmospheric transport and chemical processes for estimating associated emissions or mole fractions. Plain Language Summary: We introduce a simplified global model that simulates the movement of gases in the atmosphere. The main goal of this model is to understand how greenhouse gases and substances that deplete the ozone layer are transported and distributed, and to more accurately estimate their global emissions using concentrations measured in the atmosphere over time. To achieve this, the model uses data from weather analysis and experiments conducted with a more complex three‐dimensional model. The model calculates how gases move across different latitudes and altitudes, and accounts for their chemical loss. The simplified model can accurately reproduce large‐scale atmospheric transport phenomena. The model is publicly available. We expect it to be useful for research that requires a fast and easy to use model to understand large‐scale atmospheric transport and related processes. Key Points: A user‐friendly 2D global atmospheric transport model using transport derived from 3D reanalysis data and flux‐gradient experimentsIntended for use with long‐lived greenhouse gases and ozone‐depleting substancesAn open‐source model, which is applicable to diverse studies on emissions and chemical processes [ABSTRACT FROM AUTHOR]