Tidal variability in the lower thermosphere: Comparison of Whole Atmosphere Model (WAM) simulations with observations from TIMED

Akmaev, R. A.; Fuller‐Rowell, T. J.; Wu, Fei; Forbes, Jeffrey M.; Zhang, X.; Anghel, A.; Iredell, Mark; Moorthi, Shrinivas; Juang, Hann‐Ming Henry

doi:10.1029/2007gl032584

Cited by 104 publications

(132 citation statements)

References 18 publications

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“…The SW2 tide excited in the middle atmosphere appears to be somewhat overestimated in WAM compared to satellite observations in the lower thermosphere, particularly at high latitudes [Akmaev et al, 2008]. It is also known to be highly sensitive to the background winds and is affected by dissipative processes on its way to the CHAMP altitudes.…”

Section: Resultsmentioning

confidence: 85%

“…Built from the operational weather prediction Global Forecast System model, it has been demonstrated to realistically reproduce important tidal waves generated in the lower atmosphere [Akmaev et al, 2008;Akmaev, 2011]. To represent the ionosphere-atmosphere interactions, WAM incorporates empirical models of plasma density [Chiu, 1975] winds at a pressure level near 400 km are taken from a climatological annual run corresponding to quiet and low solar and geomagnetic conditions.…”

Section: Data and Analysismentioning

confidence: 99%

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Thermospheric zonal mean winds and tides revealed by CHAMP

Lieberman

Akmaev²,

Fuller‐Rowell

et al. 2013

Geophysical Research Letters

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[1] We present direct, global observations of longitudinally averaged CHAMP zonal winds gathered between 2003 and 2007. A diurnal variation dominates the global zonal wind. Westward flows are observed from the early morning through afternoon hours, while eastward flows peak in the evening. A semidiurnal harmonic is also present, with magnitudes that are approximately one third of the diurnal harmonic. The time mean wind indicates westward winds over much of the globe, with weak superrotation (+E, or eastward winds) that is symmetric about the equator during equinox, and confined to the winter hemisphere at solstice. Diurnal and time mean CHAMP winds agree fairly well with the Whole Atmosphere Model. Some differences are observed in the semidiurnal and higher-order tidal winds, that underscore the challenges of modeling the sources, sinks, and mean wind effects upon tides between the surface and 400 km. Citation: Lieberman, R. S., R. A. Akmaev, T. J.Fuller-Rowell, and E. Doornbos (2013), Thermospheric zonal mean winds and tides revealed by CHAMP, Geophys. Res. Lett.,

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Section: Resultsmentioning

confidence: 85%

Section: Data and Analysismentioning

confidence: 99%

Thermospheric zonal mean winds and tides revealed by CHAMP

Lieberman

Akmaev²,

Fuller‐Rowell

et al. 2013

Geophysical Research Letters

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“…The most obvious source of heating variations is latent heat release in the tropical region (Hagan and Forbes 2002;Hagan et al 2009). The presence of a DE3 tide has been attributed to the heating distribution, in particular to the alternating high and low rates of latent heat release due to the alternating continents and ocean with longitude in the equatorial region (Hagan et al 2009;Akmaev et al 2008).…”

Section: Nonmigrating Tidesmentioning

confidence: 99%

Global Dynamics of the MLT

2012

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The transition between the middle atmosphere and the thermosphere is known as the MLT region (for mesosphere and lower thermosphere). This area has some characteristics that set it apart from other regions of the atmosphere. Most notably, it is the altitude region with the lowest overall temperature and has the unique characteristic that the temperature is much lower in summer than in winter. The summer-to-winter-temperature gradient is the result of adiabatic cooling and warming associated with a vigorous circulation driven primarily by gravity waves. Tides and planetary waves also contribute to the circulation and to the large dynamical variability in the MLT. The past decade has seen much progress in describing and understanding the dynamics of the MLT and the interactions of dynamics with chemistry and radiation. This review describes recent observations and numerical modeling as they relate to understanding the dynamical processes that control the MLT and its variability. Results from the Whole Atmosphere Community Climate Model (WACCM), which is a comprehensive high-top general circulation model with interactive chemistry, are used to illustrate the dynamical processes. Selected observations from the Sounding the Atmosphere with Broadband Emission Radiometry (SABER) instrument are shown for comparison. WACCM simulations of MLT dynamics have some differences with observations. These differences and other questions and discrepancies described in recent papers point to a number of ongoing uncertainties about the MLT dynamical system.

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“…Recently, the GCMs have become ones which are coupled with models of the ionosphere, magnetosphere, and the lower atmosphere (e.g., Roble, 2000;Fujiwara, 2003, 2009;Wang et al, 2004;Toth et al, 2007;Akmaev et al, 2008;. These models are now essential for space weather researches to understand effects of the solar activity on the geospace environment.…”

Section: Introductionmentioning

confidence: 99%

Thermospheric temperature and density variations

Fujiwara¹,

Miyoshi²,

Jin³

et al. 2009

Proc. IAU

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Abstract. The thermosphere is the transition region from the atmosphere to space. Both the solar ultraviolet radiation and the solar wind energy inputs have caused significant thermospheric variations from past to present. In order to understand thermospheric/ionospheric disturbances in association with changes in solar activity, observational and modelling efforts have been made by many researchers. Recent satellite observations, e.g., the satellite CHAMP, have revealed mass density variations in the upper thermosphere. The thermospheric temperature, wind, and composition variations have been also investigated with general/global circulation models (GCMs) which include forcings due to the solar wind energy inputs and the lower atmospheric effects. In particular, we have developed a GCM which covers all the atmospheric regions, troposphere, stratosphere, mesosphere, and thermosphere, to describe variations of the thermospheric temperature and density caused by both effects from the lower atmosphere and the magnetosphere. GCM simulations represent global and localized temperature and density structures, which vary from hour to hour, depending on forcings due to the lower atmosphere, solar and geomagnetic activities. This modelling attempt will enable us to describe the thermospheric weather influenced by solar activity in cooperation with ground-based and satellite observations.

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Tidal variability in the lower thermosphere: Comparison of Whole Atmosphere Model (WAM) simulations with observations from TIMED

Cited by 104 publications

References 18 publications

Thermospheric zonal mean winds and tides revealed by CHAMP

Thermospheric zonal mean winds and tides revealed by CHAMP

Global Dynamics of the MLT

Thermospheric temperature and density variations

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