Terdiurnal tide in the extended Canadian Middle Atmospheric Model (CMAM)

Abstract

[1] We use the extended Canadian Middle Atmosphere Model (CMAM), a general circulation model (GCM), to investigate the nature of the terdiurnal tide. Temperature and horizontal winds from a model run are analyzed to delineate the character of this tide for zonal wave numbers s = −5 to +5. Descriptions of the annual mean amplitudes, seasonal variations, and total tide superposed from the migrating and 10 nonmigrating components are provided. The amplitudes and vertical wavelengths of the various components and the total terdiurnal tide are found to depend strongly on season, latitude, and altitude. The migrating terdiurnal component maximizes at mid and high latitudes with significant amplitudes (annual mean amplitude in wind (temperature) >10 m/s (K)) in the upper mesosphere and lower thermosphere (MLT) region. Between 80 and 100 km, maximum amplitudes occur in winter in both hemispheres, whereas above 100 km, maximum amplitudes occur during solstices. For the zonal wind field, the nonmigrating terdiurnal components Te5, Te3, Te4, Tw4, and Tw5 tend to peak at >50°N/S with amplitudes between 2 and 8 m/s. The other nonmigrating components maximize in the polar regions with amplitudes of 2-10 m/s. Possible generation mechanisms (solar heating and nonlinear interactions) for the migrating terdiurnal tide in the MLT region are also examined. Correlation analysis indicates that nonlinear interactions between the migrating diurnal and semidiurnal tides are unlikely to be the source of the migrating terdiurnal tide.

Physical mechanisms responsible for forming the 4-peak longitudinal structure of the 135.6nm ionospheric emission: First results from the Canadian IAM

“…This was followed by a paper which described the physical parameterizations and presented a zonal mean climatology and energy budget from the extended CMAM (Fomichev et al, 2002). Nonmigrating tides generated by the CMAM and observed in the MLT region were discussed by Ward et al (2005), and papers by Du et al (2007) and Du and Ward (2010) showed that the semidiurnal and terdiurnal tidal signatures were realistic. McLandress et al (2006) analyzed the large-scale dynamics of the MLT region simulated by the model.…”

Global Dynamics of the MLT

“…Taylor et al (1999) reported a large amplitude terdiurnal (8-h) tide in temperature data from an airglow imager. Younger et al (2000) and Du and Ward (2005) presented the global and seasonal structure of the terdiurnal tide in horizontal winds observed by HRDI and WINDII, respectively. Modeling studies by Smith and Ortland (2001) and Akmaev (2001a) indicated that the mean terdiurnal tide is primarily forced by solar heating although generation by nonlinear interaction between diurnal and semidiurnal migrating tides also contributed.…”

The diurnal and semidiurnal tides over Ascension Island (° S, 14° W) and their interaction with the stratospheric quasi-biennial oscillation: studies with meteor radar, eCMAM and WACCM

“…The terdiurnal tide generally reaches smaller amplitudes, but can nevertheless be significant (e.g. Teitelbaum et al, 1989;Younger et al, 2002;Du and Ward, 2010).…”