Solar Diurnal Tides and the Induced Zonal Mean Flows By Saburo Miyahara

Miyahara, S.

doi:10.2151/jmsj1965.58.4_302

Cited by 9 publications

(2 citation statements)

References 11 publications

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“…It was recognized early on through calculation of net heat and momentum flux divergences (e.g., Lindzen & Blake, 1970;Teitelbaum & Vial, 1981;Groves & Forbes, 1985;Vial & Teitelbaum, 1986;Miyahara et al, 1991;Lieberman & Hays, 1994) that dissipating tides might constitute an important source of net heating and/or acceleration in the lower thermosphere. Nonlinear models of the time (i.e., Miyahara, 1978aMiyahara, , 1978bMiyahara, , 1980Miyahara, , 1981Miyahara & Wu, 1989) quantified the induced zonally and diurnally averaged (hereafter referred to as the "zonal-mean") zonal winds in the lower thermosphere due to dissipating diurnal and semidiurnal migrating (i.e., Sun-synchronous) tides and demonstrated that tidal dissipation produced changes in the zonal-mean zonal winds on the order of tens of meters per second. Progressively more sophisticated models (e.g., Angelats i Coll Forbes et al, 1993;Hagan et al, 2009;Jones et al, 2014a) have produced similar-amplitude (10-40 m/s) mean winds, including those produced by nonmigrating tides.…”

Section: Introductionmentioning

confidence: 99%

The Effects of Vertically Propagating Tides on the Mean Dynamical Structure of the Lower Thermosphere

2019

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Numerical experiments performed with the National Center for Atmospheric Research thermosphere‐ionosphere‐electrodynamics general circulation model forced with an observationally based diurnal and semidiurnal tidal spectrum are utilized to investigate the physical processes by which the dissipation of vertically propagating tides act to alter the zonally and diurnally averaged (“zonal‐mean”) dynamical state of the thermosphere. Below 150 km the largest contributors to the zonal‐mean zonal wind distribution are the pressure gradient, Coriolis, and the tidally driven momentum flux divergence terms, the latter being about half the former two. Ion drag plays a smaller role in the lower thermosphere but becomes increasingly important at higher altitudes (i.e., above ∼150 km). We also find that the tidally driven heat flux divergence term contributes to the generation of zonal‐mean zonal winds through its coupling into the pressure gradient term. Tidally induced zonally and diurnally averaged zonal wind changes achieve values of up to 30 m/s in the lower thermosphere, of which about a third can be traced to the heat flux divergence. Tidal amplitudes used to force the thermosphere‐ionosphere‐electrodynamics general circulation model lower boundary represent conservative estimates, since they are based on forcing by a multiyear 60‐day mean tidal climatology, which significantly underestimates their amplitudes at any given time. Eliassen‐Palm Fluxes further support the conclusion that the heat flux divergence has a statistically significant direct impact on the zonal‐mean zonal wind balance in the lower thermosphere.

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Section: Introductionmentioning

confidence: 99%

The Effects of Vertically Propagating Tides on the Mean Dynamical Structure of the Lower Thermosphere

2019

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“…For a more complete description of classical tidal theory, we refer the reader to Chapman and Lindzen []. Past studies [ Miyahara , , , , ; Miyahara and Wu , ; Miyahara et al , ; Forbes et al , , , ; Groves and Forbes , , ; Hagan et al , ; Teitelbaum and Vial , ] have focused on evaluating and estimating the energy and momentum deposition associated with atmospheric tides and its effects on the zonal mean structure of the IT system. Specifically, Forbes et al [] utilized the National Center for Atmospheric Research (NCAR) thermosphere‐ionosphere general circulation model (TIGCM) [e.g., Roble et al , ] with and without observationally based tidal lower boundary conditions (∼97 km) to quantify the net acceleration, heating, and compositional changes in the IT due to upward propagating migrating (i.e., Sun‐synchronous) tides.…”

Section: Introductionmentioning

confidence: 99%

Impacts of vertically propagating tides on the mean state of the ionosphere‐thermosphere system

et al. 2014

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General Circulation Model (TIE-GCM) is utilized to understand the role that upward propagating tides play in determining the zonal mean state of the ionosphere-thermosphere system. A sensitivity assessment of the TIE-GCM shows that TIE-GCM solutions greatly depend on the lower boundary conditions. We also establish the veracity of our TIE-GCM solutions within and above the dynamo region. To isolate the mean effects of tidal dissipation, differences between TIE-GCM simulations with and without lower boundary tidal forcing as specified by the Climatological Tidal Model of the Thermosphere are investigated. Dissipation of the DW1, (diurnal westward propagating tide with zonal wave number 1), diurnal eastward propagating tide with zonal wave number 3, and SW2 (semidiurnal tide with zonal wave number 2) explains most of ∼10-30 m s −1 seasonal and latitudinal variability in zonal winds within the dynamo region, with SW2 playing a greater role than ascribed in previous studies. Tidal dissipation at low latitudes causes a 9% decrease (30% increase) in [O] ([O 2 ]) number densities near the F 2 layer peak, leading to at least a 9% decrease in peak electron density (N m F 2 ) throughout the year. F 2 layer peak height (h m F 2 ) differences of -4 to 2 km at low latitudes are explained by variations in the field-aligned plasma motion driven by meridional wind differences induced by tidal dissipation. Compositional effects are mainly driven by DW1 and SW2, which differs from previous interpretations of tidal-driven composition changes by DW1 "tidal mixing" exclusively. We suggest that tides may produce a net transport of constituents in the thermosphere similar to the way that, e.g., gravity waves can drive net transport of sodium in the mesosphere.

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Zonal Mean Winds Induced by Solar Diurnal Tides in the Lower Thermosphere for a Solstice Condition

Miyahara¹

1984

Dynamics of the Middle Atmosphere

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Solar Diurnal Tides and the Induced Zonal Mean Flows By Saburo Miyahara

Cited by 9 publications

References 11 publications

The Effects of Vertically Propagating Tides on the Mean Dynamical Structure of the Lower Thermosphere

The Effects of Vertically Propagating Tides on the Mean Dynamical Structure of the Lower Thermosphere

Impacts of vertically propagating tides on the mean state of the ionosphere‐thermosphere system

Zonal Mean Winds Induced by Solar Diurnal Tides in the Lower Thermosphere for a Solstice Condition

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