Migrating Semidiurnal Tide During the September Equinox Transition in the Northern Hemisphere

N. M. Pedatella, H. L. Liu, J. F. Conte, J. L. Chau, C. Hall, C. Jacobi, N. Mitchell, M. Tsutsumi

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15 Citations (SciVal)

Abstract

Specified Dynamics Whole Atmosphere Community Climate Model with thermosphere-ionosphere eXtension simulations are used to investigate the solar migrating semidiurnal tide (SW2) around September equinox at middle to high latitudes in the Northern Hemisphere. A pronounced minimum in SW2 occurs around September equinox, and is characterized by a ∼50% reduction in tidal amplitudes for 20–30 days. Analysis of the simulation results indicates that the SW2 minimum occurs due to the seasonal transition of the zonal mean zonal winds, which alter the generation and propagation of different symmetric and antisymmetric modes of SW2. In particular, the antisymmetric modes notably decrease due to the more hemispherically symmetric zonal winds around equinox. It is further demonstrated that interannual variability in the timing of the SW2 minimum is related to the timing of the seasonal transition of the zonal mean zonal winds in the middle atmosphere. This leads to an earlier occurrence of the SW2 minimum during years when the seasonal transition occurs earlier, such as the recent 2019 September equinox which saw an earlier transition of the Southern Hemisphere zonal mean zonal winds following the occurrence of a sudden stratosphere warming. The connection between the timing of the SW2 minimum in the Northern Hemisphere and the timing of the seasonal transition in the middle atmosphere winds is confirmed by seasonal variability of 12-h tides deduced from specular meteor radar observations at middle to high latitudes in the Northern Hemisphere.

Original languageEnglish
Article numbere2020JD033822
JournalJournal of Geophysical Research: Atmospheres
Volume126
Issue number3
Early online date30 Dec 2020
DOIs
Publication statusPublished - 16 Feb 2021

Bibliographical note

Funding Information:
WACCMX is part of the Community Earth System Model (CESM) and the source code is available at http://www.cesm.ucar.edu. The SD-WACCMX simulation output is available via https://doi.org/10.26024/5b58-nc53. The meteor radar observations of the semidiurnal tide are available via https://doi.org/10.5065/wf44-qr97. We would like to acknowledge high-performance computing support from Cheyenne (doi:10.5065/D6RX99HX) provided by NCAR's Computational and Information Systems Laboratory. We thank the NASA Global Modeling and Assimilation Office (GMAO) for making available the MERRA-2 data available (via https://disc.sci.gsfc.nasa.gov/), which is used to constrain the SD-WACCMX simulations. This material is based upon work supported by the National Center for Atmospheric Research, which is a major facility sponsored by the U.S. National Science Foundation under Cooperative Agreement 1852977. N. P. acknowledges support from National Science Foundation Grant AGS-1552153 and NASA Grant 80NSSC18K1046. H. L. acknowledges partial support from National Science Foundation Grant OPP-1443726. The participation of J. L. C. and J.F. C in this work is supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under SPP 1788 (DynamicEarth)-CH 1482/2 (DYNAMITE2).

Publisher Copyright:
© 2020. American Geophysical Union. All Rights Reserved.

Copyright:
Copyright 2021 Elsevier B.V., All rights reserved.

Keywords

  • mesosphere
  • semidiurnal tide
  • whole atmosphere model

ASJC Scopus subject areas

  • Atmospheric Science
  • Geophysics
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science

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