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Volume 18, issue 10
Atmos. Chem. Phys., 18, 7169-7187, 2018
https://doi.org/10.5194/acp-18-7169-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Special issue: The SPARC Reanalysis Intercomparison Project (S-RIP) (ACP/ESSD...

Atmos. Chem. Phys., 18, 7169-7187, 2018
https://doi.org/10.5194/acp-18-7169-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 24 May 2018

Research article | 24 May 2018

A comparison of the momentum budget in reanalysis datasets during sudden stratospheric warming events

Patrick Martineau1, Seok-Woo Son2, Masakazu Taguchi3, and Amy H. Butler4 Patrick Martineau et al.
  • 1Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo, Japan
  • 2School of Earth and Environmental Sciences, Seoul National University, Seoul, South Korea
  • 3Department of Earth Science, Aichi University of Education, Kariya, Japan
  • 4Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, USA

Abstract. The agreement between reanalysis datasets, in terms of the zonal-mean momentum budget, is evaluated during sudden stratospheric warming (SSW) events. It is revealed that there is a good agreement among datasets in the lower stratosphere and troposphere concerning zonal-mean zonal wind, but less so in the upper stratosphere. Forcing terms of the momentum equation are also relatively similar in the lower atmosphere, but their uncertainties are typically larger than uncertainties of the zonal-wind tendency. Similar to zonal-wind tendency, the agreement among forcing terms is degraded in the upper stratosphere. Discrepancies among reanalyses increase during the onset of SSW events, a period characterized by unusually large fluxes of planetary-scale waves from the troposphere to the stratosphere, and decrease substantially after the onset. While the largest uncertainties in the resolved terms of the momentum budget are found in the Coriolis torque, momentum flux convergence also presents a non-negligible spread among the reanalyses. Such a spread is reduced in the latest reanalysis products, decreasing the uncertainty of the momentum budget. It is also found that the uncertainties in the Coriolis torque depend on the strength of SSW events: the SSW events that exhibit the most intense deceleration of zonal-mean zonal wind are subject to larger discrepancies among reanalyses. These uncertainties in stratospheric circulation, however, are not communicated to the troposphere.

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This study evaluates the agreement between eight reanalysis datasets by comparing zonal-mean zonal winds and the forcing terms of the zonal-mean momentum equation during sudden stratospheric warming events. Results show that the spread between datasets increases exponentially with height and is largest during the most intense sudden stratospheric warming events. The largest uncertainties arise from differences in the mean meridional circulation and horizontal fluxes of momentum by eddies.
This study evaluates the agreement between eight reanalysis datasets by comparing zonal-mean...
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