Editors’ Highlights are summaries of recent papers by AGU’s journal editors.
Source: Journal of Advances in Modeling Earth Systems
Chlorofluorocarbons (CFCs) are ozone-depleting substances whose production and emission have been curtailed by the Montreal Protocol international agreement. Scientists have long used atmospheric transport models, along with observations of CFCs in the atmosphere, to detect where emissions of CFCs and other ozone-depleting chemicals are taking place. Some of these models are very simple to use but are not very accurate due to their low resolution and constant-in-time transport, while other 3-dimensional models are more accurate but complex and require lots of computer power and specialized training to run.
Western et al. [2024] present a new model of intermediate complexity (MALTA: Model of Averaged in Longitude Transport in the Atmosphere) that captures pole-to-pole and year-to-year variations in atmospheric transport in an accurate way, but is much faster and easier to run than complex 3-dimensional models. To build this new 2-dimensional model, the authors incorporated atmospheric circulation and mixing rates from more complex models that represent our best state of knowledge of atmospheric transport. Using this simplified model, they could accurately deduce the rate and pattern of CFC emissions from a more complex model.
Importantly, the model captures year-to-year variations in the atmospheric transport that are missed by simple constant-in-time models. One example is the quasi-biennial oscillation (QBO), a periodic shift in the wind directions in the tropical stratosphere. MALTA accurately captured the effects of the QBO on atmospheric CFC-11 concentrations (see image above), an important step for getting accurate estimates of CFC-11 emissions. This open-source model will also be useful for modeling other long-lived atmospheric trace gases such as methane, nitrous oxide, and other halocarbons.
Citation: Western, L. M., Bachman, S. D., Montzka, S. A., & Rigby, M. (2024). MALTA: A zonally averaged global atmospheric transport model for long-lived trace gases. Journal of Advances in Modeling Earth Systems, 16, e2023MS003909. https://doi.org/10.1029/2023MS003909
—Timothy DeVries, Associate Editor, JAMES