Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Atmos. Chem. Phys., 16, 6131-6152, 2016
https://doi.org/10.5194/acp-16-6131-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
20 May 2016
Inter-comparison of stratospheric mean-meridional circulation and eddy mixing among six reanalysis data sets
Kazuyuki Miyazaki1, Toshiki Iwasaki2, Yoshio Kawatani1, Chiaki Kobayashi3, Satoshi Sugawara4, and Michaela I. Hegglin5 1Japan Agency for Marine-Earth Science and Technology, Yokohama, Japan
2Department of Geophysics, Graduate School of Science, Tohoku University, Sendai, Japan
3Meteorological Research Institute, Tsukuba, Japan
4Department of Science Education, Miyagi University of Education, Sendai, Japan
5Department of Meteorology, University of Reading, Reading, UK
Abstract. The stratospheric mean-meridional circulation (MMC) and eddy mixing are compared among six meteorological reanalysis data sets: NCEP-NCAR, NCEP-CFSR, ERA-40, ERA-Interim, JRA-25, and JRA-55 for the period 1979–2012. The reanalysis data sets produced using advanced systems (i.e., NCEP-CFSR, ERA-Interim, and JRA-55) generally reveal a weaker MMC in the Northern Hemisphere (NH) compared with those produced using older systems (i.e., NCEP/NCAR, ERA-40, and JRA-25). The mean mixing strength differs largely among the data products. In the NH lower stratosphere, the contribution of planetary-scale mixing is larger in the new data sets than in the old data sets, whereas that of small-scale mixing is weaker in the new data sets. Conventional data assimilation techniques introduce analysis increments without maintaining physical balance, which may have caused an overly strong MMC and spurious small-scale eddies in the old data sets. At the NH mid-latitudes, only ERA-Interim reveals a weakening MMC trend in the deep branch of the Brewer–Dobson circulation (BDC). The relative importance of the eddy mixing compared with the mean-meridional transport in the subtropical lower stratosphere shows increasing trends in ERA-Interim and JRA-55; this together with the weakened MMC in the deep branch may imply an increasing age-of-air (AoA) in the NH middle stratosphere in ERA-Interim. Overall, discrepancies between the different variables and trends therein as derived from the different reanalyses are still relatively large, suggesting that more investments in these products are needed in order to obtain a consolidated picture of observed changes in the BDC and the mechanisms that drive them.

Citation: Miyazaki, K., Iwasaki, T., Kawatani, Y., Kobayashi, C., Sugawara, S., and Hegglin, M. I.: Inter-comparison of stratospheric mean-meridional circulation and eddy mixing among six reanalysis data sets, Atmos. Chem. Phys., 16, 6131-6152, https://doi.org/10.5194/acp-16-6131-2016, 2016.
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Short summary
We report a comparison of the stratospheric mean-meridional circulation and eddy mixing in the stratospheric Brewer-Dobson circulation (BDC) among the six reanalysis products. Overall, discrepancies between the different variables and trends therein as derived from the different reanalyses are still relatively large, suggesting that more investments in these products are needed in order to obtain a consolidated picture of observed changes in the BDC and the mechanisms that drive them.
We report a comparison of the stratospheric mean-meridional circulation and eddy mixing in the...
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