Mesospheric non-migrating tides generated with planetary waves: I. Characteristics

• Published in: Journal of atmospheric and solar-terrestrial physics Vol. 67; no. 11; pp. 959 - 980
• Main Authors: Mayr, H.G., Mengel, J.G., Talaat, E.R., Porter, H.S., Chan, K.L.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.07.2005; Elsevier
• Subjects: Earth, ocean, space; Exact sciences and technology; External geophysics; Gravity waves; Mesosphere dynamics; Non-migrating tides; Numerical modeling; Physics of the high neutral atmosphere; Physics of the ionosphere; Physics of the magnetosphere; Numerical modeling; Mesosphere dynamics; Non-migrating tides; Gravity waves; Non linear coupling; Thermosphere; Spectral model; digital simulation; Mesosphere; Parameterization; troposphere; Modeling; Heat liberation; convection; dynamics; Planetary wave; Quasi biennial oscillation; Latent heat; Solar tide; Excitation source; Gravity wave; instability; warming; seasonal variations; Wave number
• ISSN: 1364-6826; 1879-1824
• DOI: 10.1016/j.jastp.2005.03.002

In light of the measurements from the TIMED spacecraft and coordinated ground-based observations, we discuss results from a modeling study with our Numerical Spectral Model (NSM), which specifically deals with the non-migrating tides generated in the mesosphere. The NSM extends from the ground to the thermosphere, incorporates Hines’ Doppler Spread Parameterization for small-scale gravity waves (GWs), and it describes the major dynamical features of the atmosphere including the wave driven equatorial oscillations (QBO and SAO), and the seasonal variations of tides and planetary waves (PWs). Accounting solely for the excitation sources of the solar migrating tides, the NSM generates through nonlinear interactions also non-migrating tides in the mesosphere that are comparable in magnitude to those observed. (The important non-migrating tides generated explicitly by processes like tropospheric latent heat release and convection are not included.) Large non-migrating tides are produced in the diurnal and semi-diurnal oscillations for the zonal mean (wave number m = 0 ) and in the semidiurnal oscillation for m = 1 . In general, significant eastward and westward propagating tides are generated for all the zonal wave numbers m = 1 –4. To identify the cause, the NSM is run without the solar heating for the zonal mean ( m = 0 ), and the amplitudes of the resulting non-migrating tides are then negligibly small. In this case, the PWs generated by instabilities are artificially suppressed. This leads to the conclusion that the non-migrating tides are produced through nonlinear interactions between PWs and migrating tides, as had been previously proposed. In the accompanying paper, we present results from numerical experiments, which demonstrate that GW filtering contributes significantly to produce the nonlinear coupling that is involved.