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Volume 18, issue 2 | Copyright

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

Atmos. Chem. Phys., 18, 1437-1456, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 01 Feb 2018

Research article | 01 Feb 2018

Representation of solar tides in the stratosphere and lower mesosphere in state-of-the-art reanalyses and in satellite observations

Takatoshi Sakazaki1,2,3, Masatomo Fujiwara4, and Masato Shiotani3 Takatoshi Sakazaki et al.
  • 1International Pacific Research Center, University of Hawai'i at Manoa, Honolulu, HI 96822, USA
  • 2Japan Society for Promotion of Science Overseas Research Fellow, Tokyo, 102-0083, Japan
  • 3Research Institute for Sustainable Humanosphere, Kyoto University, Uji, 611-0011, Japan
  • 4Faculty of Environmental Earth Science, Hokkaido University, Sapporo, 060-0810, Japan

Abstract. Atmospheric solar tides in the stratosphere and the lower mesosphere are investigated using temperature data from five state-of-the-art reanalysis data sets (MERRA-2, MERRA, JRA-55, ERA-Interim, and CFSR) as well as TIMED SABER and Aura MLS satellite measurements. The main focus is on the period 2006–2012 during which the satellite observations are available for direct comparison with the reanalyses. Diurnal migrating tides, semidiurnal migrating tides, and nonmigrating tides are diagnosed. Overall the reanalyses agree reasonably well with each other and with the satellite observations for both migrating and nonmigrating components, including their vertical structure and the seasonality. However, the agreement among reanalyses is more pronounced in the lower stratosphere and relatively weaker in the upper stratosphere and mesosphere. A systematic difference between SABER and the reanalyses is found for diurnal migrating tides in the upper stratosphere and the lower mesosphere; specifically, the amplitude of trapped modes in reanalyses is significantly smaller than that in SABER, although such difference is less clear between MLS and the reanalyses. The interannual variability and the possibility of long-term changes in migrating tides are also examined using the reanalyses during 1980–2012. All the reanalyses agree in exhibiting a clear quasi-biennial oscillation (QBO) in the tides, but the most significant indications of long-term changes in the tides represented in the reanalyses are most plausibly explained by the evolution of the satellite observing systems during this period. The tides are also compared in the full reanalyses produced by the Japan Meteorological Agency (i.e., JRA-55) and in two parallel data sets from this agency: one (JRA-55C) that repeats the reanalysis procedure but without any satellite data assimilated and one (JRA-55AMIP) that is a free-running integration of the model constrained only by observed sea surface temperatures. Many aspects of the tides are closer in JRA-55C and JRA-55AMIP than these are to the full reanalysis JRA-55, demonstrating the importance of the assimilation of satellite data in representing the diurnal variability of the middle atmosphere. In contrast to the assimilated data sets, the free-running model has no QBO in equatorial stratospheric mean circulation and our results show that it displays no quasi-biennial variability in the tides.

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Atmospheric solar tides in the stratosphere and lower mesosphere are examined using temperature data from five reanalyses and satellite measurements. The reanalyses agree reasonably well with each other and with the satellite observations, but the agreement among the reanalyses is weaker in the mesosphere. The assimilation of satellite data improves the representation of tides in the reanalyses, while long-term changes are mostly artificial and driven by changes in the input data employed.
Atmospheric solar tides in the stratosphere and lower mesosphere are examined using temperature...