Abstract
The nonmigrating diurnal tide, DW2, is known to have a source from the stationary planetary wave with wavenumber 1 (SPW1) and the migrating diurnal tide (DW1) interaction. Recent research has shown that DW2 time evolution in the equatorial mesopause tracks very well with SPW1 in the polar stratosphere for the winter of 2009–2010, which contains a sudden stratospheric warming (SSW) vortex split event. This paper extends previous research and investigates the relationship between these two waves for 31 winters from 1979 to 2010 with the extended Canadian Middle Atmosphere Model (eCMAM) through correlation and composite analysis. Significant correlations are present between the two waves in 20 out of 31 winters (65%). We separate the 31 winters into four categories: SSW-displacement, SSW-split, minor-SSW, and no-SSW. Our results show that there is no significant difference among the four categories in terms of correlations between the two waves. Although SPW1 is usually stronger during a SSW-D winter, this does not warrant a stronger interaction with DW2.
Highlights
It is becoming increasingly clear that understanding wave driving from below is critical for predicting large and small scale structures in the ionosphere and thermosphere (IT) system, such as ionospheric scintillations important to communication and navigation, and testing and improving models for orbit propagation and collision warnings
Results with the extended Canadian Middle Atmosphere Model (eCMAM) data to evaluate again the NOGAPS and SABER used in Lieberman et al (2015)
The eCMAM simulations for the same event are compared to both the shows the evolution of stratospheric stationary planetary wave with wavenumber 1 (SPW1) geopotential height (Z) amplitude, zonal mean temperature
Summary
It is becoming increasingly clear that understanding wave driving from below is critical for predicting large and small scale structures in the ionosphere and thermosphere (IT) system, such as ionospheric scintillations important to communication and navigation, and testing and improving models for orbit propagation and collision warnings. The relevant coupling processes operating within the neutral atmosphere, and between the neutral atmosphere and ionosphere, involve a host of multi-scale dynamics that are not fully understood at present [1]. Atmospheric tide is one of the key players for inducing the multi-scale dynamics in the IT system. Solar heating can be approximated by a rectified cosine profile so that Fourier transformation can be used to decompose the tidal components into periods of sub-harmonics of a solar day: Diurnal (24 h), semidiurnal (12 h), and terdiurnal (8 h) etc. Migrating (sun-synchronous) tides propagate westward with the apparent motion of the Sun. Nonmigrating tides do not follow the apparent motion of the Sun and can propagate westward, eastward, or be stationary. Different tidal components are identified as follows: “DWs” or “Des” denotes a westward or eastward propagating diurnal tide, Atmosphere 2018, 9, 416; doi:10.3390/atmos9110416 www.mdpi.com/journal/atmosphere
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