Speaker
Description
We present an intercomparison of the mean age of air (AoA) derived from three recent reanalyses: the European Centre for Medium-Range Weather Forecasts Reanalysis version 5 (ERA5) and its predecessor (ERA-Interim), the National Aeronautics and Space Administration’s Modern-Era Retrospective analysis for Research and Applications version 2 (MERRA2), and the Japan Meteorological Agency’s 3-Quarter Century Reanalysis (JRA-3Q). AoA is computed using an idealized clock tracer within the Belgian Assimilation System for Chemical Observations (BASCOE) chemistry transport model.
We examine the simulated AoA time series with a particular focus on differences between the reanalyses. Preliminary results indicate that MERRA2 and JRA-3Q show a decreasing AoA trend between 1990 and 2000, after which all three reanalyses exhibit a relatively stable AoA with no significant trends. ERA5 consistently provides the youngest AoA, suggesting a faster stratospheric transport. These findings are compared with the results of Chabrillat et al. (2018), which analyzed older reanalysis versions (ERA-Interim and JRA-55) using a previous version of the BASCOE model, and with Ploeger et al. (2019, 2021), which presented AoA from the CLaMS model driven by ERA-Interim, MERRA2, JRA-55 and ERA5. We also compare with existing limb retrievals of age of air from MIPAS and ACE-FTS, as well as mock retrievals from the future CAIRT mission, which is currently in phase A of development.
This study provides insights into the evolution of AoA estimates in successive reanalysis products and highlights key differences in stratospheric transport representations.
| Topic | Atmospheric composition (Earth and planets), chemistry and transport |
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