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Erdal Yigit - One of the best experts on this subject based on the ideXlab platform.
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influence of parameterized small scale gravity waves on the migrating diurnal tide in earth s Thermosphere
Journal of Geophysical Research, 2017Co-Authors: Erdal Yigit, Alexander S MedvedevAbstract:Effects of subgrid-scale gravity waves (GWs) on the diurnal migrating tides are investigated from the mesosphere to the upper Thermosphere for September equinox conditions, using a general circulation model coupled with the extended spectral nonlinear GW parameterization of Yigit et al. [2008].. Simulations with GW effects cut-off above the turbopause and included in the entire Thermosphere have been conducted. GWs appreciably impact the mean circulation and cool the Thermosphere down by up to 12-18%. GWs significantly affect the winds modulated by the diurnal migrating tide, in particular in the low-latitude mesosphere and lower Thermosphere and in the high-latitude Thermosphere. These effects depend on the mutual correlation of the diurnal phases of the GW forcing and tides: GWs can either enhance or reduce the tidal amplitude. In the low-latitude MLT, the correlation between the direction of the deposited GW momentum and the tidal phase is positive due to propagation of a broad spectrum of GW harmonics through the alternating winds. In the Northern Hemisphere high-latitude Thermosphere, GWs act against the tide due to an anti-correlation of tidal wind and GW momentum, while in the Southern high-latitudes they weakly enhance the tidal amplitude via a combination of a partial correlation of phases and GW-induced changes of the circulation. The variable nature of GW effects on the thermal tide can be captured in GCMs provided that a GW parameterization (1) considers a broad spectrum of harmonics, (2) properly describes their propagation, and (3) correctly accounts for the physics of wave breaking/saturation.
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global distribution and parameter dependences of gravity wave activity in the martian upper Thermosphere derived from maven ngims observations
Journal of Geophysical Research, 2017Co-Authors: Naoki Terada, Alexander S Medvedev, Erdal Yigit, Hitoshi Fujiwara, Francois Leblanc, Hiromu Nakagawa, Takeshi Kuroda, T Hara, S England, Kaori TeradaAbstract:Wavelike perturbations in the Martian upper Thermosphere observed by the Neutral Gas Ion Mass Spectrometer (NGIMS) onboard the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft have been analyzed. The amplitudes of small-scale perturbations with apparent wavelengths between ~100 and ~500 km in the Ar density around the exobase show a clear dependence on temperature (T0) of the upper Thermosphere. The average amplitude of the perturbations is ~10% on the dayside and ~20% on the nightside, which is about 2 and 10 times larger than those observed in the Venusian upper Thermosphere and in the low-latitude region of Earth's upper Thermosphere, respectively. The amplitudes are inversely proportional to T0, suggesting saturation due to convective instability in the Martian upper Thermosphere. After removing the dependence on T0, dependences of the average amplitude on the geographic latitude and longitude and solar wind parameters are found to be not larger than a few percent. These results suggest that the amplitudes of small-scale perturbations are mainly determined by convective breaking/saturation in the upper Thermosphere on Mars, unlike those on Venus and Earth.
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Global distribution and parameter dependences of gravity wave activity in the Martian upper Thermosphere derived from MAVEN/NGIMS observations
Journal of Geophysical Research Space Physics, 2017Co-Authors: Naoki Terada, Scott L England, Alexander S Medvedev, Erdal Yigit, Hitoshi Fujiwara, Francois Leblanc, Hiromu Nakagawa, Takeshi Kuroda, T Hara, Kaori TeradaAbstract:Wavelike perturbations in the Martian upper Thermosphere observed by the Neutral Gas Ion Mass Spectrometer (NGIMS) onboard the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft have been analyzed. The amplitudes of small-scale perturbations with apparent wavelengths between ~100 and ~500 km in the Ar density around the exobase show a clear dependence on temperature (T0) of the upper Thermosphere. The average amplitude of the perturbations is ~10% on the dayside and ~20% on the nightside, which is about 2 and 10 times larger than those observed in the Venusian upper Thermosphere and in the low-latitude region of Earth's upper Thermosphere, respectively. The amplitudes are inversely proportional to T0, suggesting saturation due to convective instability in the Martian upper Thermosphere. After removing the dependence on T0, dependences of the average amplitude on the geographic latitude and longitude and solar wind parameters are found to be not larger than a few percent. These results suggest that the amplitudes of small-scale perturbations are mainly determined by convective breaking/saturation in the upper Thermosphere on Mars, unlike those on Venus and Earth.
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simulated variability of the high latitude Thermosphere induced by small scale gravity waves during a sudden stratospheric warming
Journal of Geophysical Research, 2014Co-Authors: Scott L England, Alexander S Medvedev, Erdal Yigit, T J ImmelAbstract:We present the results of the first investigation of the influence of small-scale gravity waves (GWs) originating in the lower atmosphere on the variability of the high-latitude Thermosphere during a sudden stratospheric warming (SSW). We use a general circulation model that incorporates the spectral GW parameterization of Yigit et al. (2008). During the warming, the GW penetration into the Thermosphere and resulting momentum deposition rates increase by up to a factor of 3–6 in the high-latitude Thermosphere. The associated temporal variability of GW dynamical effects at ~250 km are enhanced by up to a factor of ~10, exhibiting complex geographical variations. The peak magnitude of the GW drag temporal variability locally exceeds the mean GW drag by more than a factor of 2. The small-scale thermospheric wind variability is larger when GW propagation into the Thermosphere is allowed compared to the case when thermospheric GW effects are absent. These results suggest that GW-induced variations during SSWs constitute a significant source of high-latitude thermospheric variability.
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general circulation modeling of the martian upper atmosphere during global dust storms
Journal of Geophysical Research, 2013Co-Authors: Alexander S Medvedev, Erdal Yigit, Takeshi Kuroda, P HartoghAbstract:[1] Simulations with a general circulation model (GCM) have been performed to study the Martian upper atmosphere during two major dust storms. The GCM extending from the surface to about 160 km included a spectral parameterization of subgrid-scale gravity waves suitable for planetary Thermospheres, and prescribed four-dimensional dust distributions corresponding to storm events near the equinox and solstice (Martian years 25 and 28, respectively). The results show that the wind and temperature fields in the upper atmosphere above ∼100 km respond to such storms as intensively as in the lower atmosphere. During the equinoctial storm, the temperature above the mesopause dropped by up to 30 K everywhere except in the Northern Hemisphere high latitudes, where it rose by up to 15 K. At the solstitial storm, the temperature above the mesopause decreased by up to 40 K in the winter hemisphere, by 15 K in the summer hemisphere, and increased by 30–40 K in tropics and in the summer hemisphere above 130 km. Prograde and retrograde zonal wind jets intensified throughout the atmosphere at all heights and during both dust scenarios. These changes are the result of the altered meridional overturning circulation induced by resolved and unresolved waves. Atmospheric density during dust storms enhanced in average by a factor of 2 to 3 in the mesosphere and lower Thermosphere, which agrees well with observations.
Alexander S Medvedev - One of the best experts on this subject based on the ideXlab platform.
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influence of parameterized small scale gravity waves on the migrating diurnal tide in earth s Thermosphere
Journal of Geophysical Research, 2017Co-Authors: Erdal Yigit, Alexander S MedvedevAbstract:Effects of subgrid-scale gravity waves (GWs) on the diurnal migrating tides are investigated from the mesosphere to the upper Thermosphere for September equinox conditions, using a general circulation model coupled with the extended spectral nonlinear GW parameterization of Yigit et al. [2008].. Simulations with GW effects cut-off above the turbopause and included in the entire Thermosphere have been conducted. GWs appreciably impact the mean circulation and cool the Thermosphere down by up to 12-18%. GWs significantly affect the winds modulated by the diurnal migrating tide, in particular in the low-latitude mesosphere and lower Thermosphere and in the high-latitude Thermosphere. These effects depend on the mutual correlation of the diurnal phases of the GW forcing and tides: GWs can either enhance or reduce the tidal amplitude. In the low-latitude MLT, the correlation between the direction of the deposited GW momentum and the tidal phase is positive due to propagation of a broad spectrum of GW harmonics through the alternating winds. In the Northern Hemisphere high-latitude Thermosphere, GWs act against the tide due to an anti-correlation of tidal wind and GW momentum, while in the Southern high-latitudes they weakly enhance the tidal amplitude via a combination of a partial correlation of phases and GW-induced changes of the circulation. The variable nature of GW effects on the thermal tide can be captured in GCMs provided that a GW parameterization (1) considers a broad spectrum of harmonics, (2) properly describes their propagation, and (3) correctly accounts for the physics of wave breaking/saturation.
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global distribution and parameter dependences of gravity wave activity in the martian upper Thermosphere derived from maven ngims observations
Journal of Geophysical Research, 2017Co-Authors: Naoki Terada, Alexander S Medvedev, Erdal Yigit, Hitoshi Fujiwara, Francois Leblanc, Hiromu Nakagawa, Takeshi Kuroda, T Hara, S England, Kaori TeradaAbstract:Wavelike perturbations in the Martian upper Thermosphere observed by the Neutral Gas Ion Mass Spectrometer (NGIMS) onboard the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft have been analyzed. The amplitudes of small-scale perturbations with apparent wavelengths between ~100 and ~500 km in the Ar density around the exobase show a clear dependence on temperature (T0) of the upper Thermosphere. The average amplitude of the perturbations is ~10% on the dayside and ~20% on the nightside, which is about 2 and 10 times larger than those observed in the Venusian upper Thermosphere and in the low-latitude region of Earth's upper Thermosphere, respectively. The amplitudes are inversely proportional to T0, suggesting saturation due to convective instability in the Martian upper Thermosphere. After removing the dependence on T0, dependences of the average amplitude on the geographic latitude and longitude and solar wind parameters are found to be not larger than a few percent. These results suggest that the amplitudes of small-scale perturbations are mainly determined by convective breaking/saturation in the upper Thermosphere on Mars, unlike those on Venus and Earth.
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Global distribution and parameter dependences of gravity wave activity in the Martian upper Thermosphere derived from MAVEN/NGIMS observations
Journal of Geophysical Research Space Physics, 2017Co-Authors: Naoki Terada, Scott L England, Alexander S Medvedev, Erdal Yigit, Hitoshi Fujiwara, Francois Leblanc, Hiromu Nakagawa, Takeshi Kuroda, T Hara, Kaori TeradaAbstract:Wavelike perturbations in the Martian upper Thermosphere observed by the Neutral Gas Ion Mass Spectrometer (NGIMS) onboard the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft have been analyzed. The amplitudes of small-scale perturbations with apparent wavelengths between ~100 and ~500 km in the Ar density around the exobase show a clear dependence on temperature (T0) of the upper Thermosphere. The average amplitude of the perturbations is ~10% on the dayside and ~20% on the nightside, which is about 2 and 10 times larger than those observed in the Venusian upper Thermosphere and in the low-latitude region of Earth's upper Thermosphere, respectively. The amplitudes are inversely proportional to T0, suggesting saturation due to convective instability in the Martian upper Thermosphere. After removing the dependence on T0, dependences of the average amplitude on the geographic latitude and longitude and solar wind parameters are found to be not larger than a few percent. These results suggest that the amplitudes of small-scale perturbations are mainly determined by convective breaking/saturation in the upper Thermosphere on Mars, unlike those on Venus and Earth.
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simulated variability of the high latitude Thermosphere induced by small scale gravity waves during a sudden stratospheric warming
Journal of Geophysical Research, 2014Co-Authors: Scott L England, Alexander S Medvedev, Erdal Yigit, T J ImmelAbstract:We present the results of the first investigation of the influence of small-scale gravity waves (GWs) originating in the lower atmosphere on the variability of the high-latitude Thermosphere during a sudden stratospheric warming (SSW). We use a general circulation model that incorporates the spectral GW parameterization of Yigit et al. (2008). During the warming, the GW penetration into the Thermosphere and resulting momentum deposition rates increase by up to a factor of 3–6 in the high-latitude Thermosphere. The associated temporal variability of GW dynamical effects at ~250 km are enhanced by up to a factor of ~10, exhibiting complex geographical variations. The peak magnitude of the GW drag temporal variability locally exceeds the mean GW drag by more than a factor of 2. The small-scale thermospheric wind variability is larger when GW propagation into the Thermosphere is allowed compared to the case when thermospheric GW effects are absent. These results suggest that GW-induced variations during SSWs constitute a significant source of high-latitude thermospheric variability.
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general circulation modeling of the martian upper atmosphere during global dust storms
Journal of Geophysical Research, 2013Co-Authors: Alexander S Medvedev, Erdal Yigit, Takeshi Kuroda, P HartoghAbstract:[1] Simulations with a general circulation model (GCM) have been performed to study the Martian upper atmosphere during two major dust storms. The GCM extending from the surface to about 160 km included a spectral parameterization of subgrid-scale gravity waves suitable for planetary Thermospheres, and prescribed four-dimensional dust distributions corresponding to storm events near the equinox and solstice (Martian years 25 and 28, respectively). The results show that the wind and temperature fields in the upper atmosphere above ∼100 km respond to such storms as intensively as in the lower atmosphere. During the equinoctial storm, the temperature above the mesopause dropped by up to 30 K everywhere except in the Northern Hemisphere high latitudes, where it rose by up to 15 K. At the solstitial storm, the temperature above the mesopause decreased by up to 40 K in the winter hemisphere, by 15 K in the summer hemisphere, and increased by 30–40 K in tropics and in the summer hemisphere above 130 km. Prograde and retrograde zonal wind jets intensified throughout the atmosphere at all heights and during both dust scenarios. These changes are the result of the altered meridional overturning circulation induced by resolved and unresolved waves. Atmospheric density during dust storms enhanced in average by a factor of 2 to 3 in the mesosphere and lower Thermosphere, which agrees well with observations.
T J Fullerrowell - One of the best experts on this subject based on the ideXlab platform.
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did the january 2009 sudden stratospheric warming cool or warm the Thermosphere
Geophysical Research Letters, 2011Co-Authors: R A Akmaev, Mariangel Fedrizzi, T J Fullerrowell, Fei Wu, Rodney ViereckAbstract:[1] It has recently been suggested that observations of neutral density from satellite accelerometer data indicate a strong cooling occurred in the upper Thermosphere during the January 2009 sudden stratospheric warming (SSW). The 2009 warming was a major event with winter polar stratospheric temperatures increasing by 70 K. This January period has been re-examined with three independent models: the NRLMSISE-00 empirical model; the physics-based coupled Thermosphere, ionosphere, plasmasphere, electrodynamics model (CTIPe); and the whole atmosphere model (WAM). The analysis of this period and comparison with the neutral density observations reveals that there is, in fact, no evidence at any latitude for a large-scale or global decrease in upper Thermosphere density or temperature in response to the SSW. The observed decrease in density and temperature can be amply accounted for by small changes in geomagnetic activity during this period. On the contrary, the WAM numerical simulations of the period suggest a possible small globally averaged upper Thermosphere warming and neutral density increase by 5% during the SSW. This warming would have been difficult to discern in the local-time sampling of the CHAMP observations due to likely change in the diurnal density variation during the SSW, and due to a much larger contribution to the variability from geomagnetic sources. At this stage, therefore, it is not possible to ascertain if a cooling or warming occurred in the upper Thermosphere in response to the stratospheric warming.
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a whole atmosphere model simulation of the impact of a sudden stratospheric warming on Thermosphere dynamics and electrodynamics
Journal of Geophysical Research, 2010Co-Authors: T J Fullerrowell, Tzuwei Fang, R A Akmaev, Fei Wu, E A AraujopradereAbstract:[1] A Whole Atmosphere Model (WAM) has been used to explore the possible physical connection between a sudden stratospheric warming (SSW) and the dynamics and electrodynamics of the lower Thermosphere. WAM produces SSWs naturally without the need for external forcing. The classical signatures of an SSW appear in the model with a warming of the winter polar stratosphere, a reversal of the temperature gradient, and a breakdown of the stratospheric polar vortex. Substantial changes in the amplitude of stationary planetary wave numbers 1, 2, and 3 occur as the zonal mean zonal wind evolves. The simulations also show a cooling in the mesosphere and a warming in the lower Thermosphere consistent with observations. The magnitude of this particular SSW is modest, belonging to the category of minor warming. In the lower Thermosphere the amplitude of diurnal, semidiurnal, and terdiurnal, eastward and westward propagating tidal modes change substantially during the event. Since the magnitude of the warming is minor and the tidal interactions with the mean flow and planetary waves are complex, the one-to-one correspondence between tidal amplitudes in the lower Thermosphere and the zonal mean and stationary waves in the stratosphere is not entirely obvious. The increase in the magnitude of the terdiurnal tide (TW3) in the lower Thermosphere has the clearest correlation with the SSW, although the timing appears delayed by about three days. The fast group velocity of the long vertical wavelength TW3 tide would suggest a faster onset for the direct propagation of the tide from the lower atmosphere. It is possible that changes in the magnitude of the diurnal and semidiurnal tides, with their slower vertical propagation, may interact in the lower Thermosphere to introduce a terdiurnal tide with a longer delay. An increase in TW3 in the lower Thermosphere would be expected to alter the local time variation of the electrodynamic response. The day-to-day changes in the lower Thermosphere winds from WAM are shown to introduce variability in the magnitude of dayside low latitude electric fields, with a tendency during the warming for the dayside vertical drift to be larger and occur earlier, and for the afternoon minimum to be smaller. The numerical simulations suggest that it is quite feasible that a major SSW, with a magnitude seen in January 2009, could cause large changes in lower Thermosphere electrodynamics and hence in total electron content.
Hitoshi Fujiwara - One of the best experts on this subject based on the ideXlab platform.
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global distribution and parameter dependences of gravity wave activity in the martian upper Thermosphere derived from maven ngims observations
Journal of Geophysical Research, 2017Co-Authors: Naoki Terada, Alexander S Medvedev, Erdal Yigit, Hitoshi Fujiwara, Francois Leblanc, Hiromu Nakagawa, Takeshi Kuroda, T Hara, S England, Kaori TeradaAbstract:Wavelike perturbations in the Martian upper Thermosphere observed by the Neutral Gas Ion Mass Spectrometer (NGIMS) onboard the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft have been analyzed. The amplitudes of small-scale perturbations with apparent wavelengths between ~100 and ~500 km in the Ar density around the exobase show a clear dependence on temperature (T0) of the upper Thermosphere. The average amplitude of the perturbations is ~10% on the dayside and ~20% on the nightside, which is about 2 and 10 times larger than those observed in the Venusian upper Thermosphere and in the low-latitude region of Earth's upper Thermosphere, respectively. The amplitudes are inversely proportional to T0, suggesting saturation due to convective instability in the Martian upper Thermosphere. After removing the dependence on T0, dependences of the average amplitude on the geographic latitude and longitude and solar wind parameters are found to be not larger than a few percent. These results suggest that the amplitudes of small-scale perturbations are mainly determined by convective breaking/saturation in the upper Thermosphere on Mars, unlike those on Venus and Earth.
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Global distribution and parameter dependences of gravity wave activity in the Martian upper Thermosphere derived from MAVEN/NGIMS observations
Journal of Geophysical Research Space Physics, 2017Co-Authors: Naoki Terada, Scott L England, Alexander S Medvedev, Erdal Yigit, Hitoshi Fujiwara, Francois Leblanc, Hiromu Nakagawa, Takeshi Kuroda, T Hara, Kaori TeradaAbstract:Wavelike perturbations in the Martian upper Thermosphere observed by the Neutral Gas Ion Mass Spectrometer (NGIMS) onboard the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft have been analyzed. The amplitudes of small-scale perturbations with apparent wavelengths between ~100 and ~500 km in the Ar density around the exobase show a clear dependence on temperature (T0) of the upper Thermosphere. The average amplitude of the perturbations is ~10% on the dayside and ~20% on the nightside, which is about 2 and 10 times larger than those observed in the Venusian upper Thermosphere and in the low-latitude region of Earth's upper Thermosphere, respectively. The amplitudes are inversely proportional to T0, suggesting saturation due to convective instability in the Martian upper Thermosphere. After removing the dependence on T0, dependences of the average amplitude on the geographic latitude and longitude and solar wind parameters are found to be not larger than a few percent. These results suggest that the amplitudes of small-scale perturbations are mainly determined by convective breaking/saturation in the upper Thermosphere on Mars, unlike those on Venus and Earth.
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impacts of sudden stratospheric warming on general circulation of the Thermosphere
Journal of Geophysical Research, 2015Co-Authors: Yasunobu Miyoshi, Hitoshi Fujiwara, Hiroyuki ShinagawaAbstract:Impacts of sudden stratospheric warming (SSW) on the Thermosphere were studied using a gravity wave (GW)-resolving whole atmosphere model. During an SSW event, the mesosphere at high latitudes cools, and the lower Thermosphere becomes warm. At the peak of the SSW event, a temperature drop occurs above an altitude of 150 km at high latitudes. Our results indicate that the SSW event strongly affects meridional circulation and GW drag in the Thermosphere. In the lower Thermosphere, upward wind in the Arctic region, southward wind in the region between the North Pole and the South Pole, and downward wind in the Antarctic region are dominant before SSW occurs. The SSW event reverses meridional circulation at altitudes between 90 and 125 km in the Northern Hemisphere. During the SSW event, downward wind in the Arctic region and northward wind in the Northern Hemisphere prevail in the lower Thermosphere. A detailed analysis revealed that during the SSW event, the change in meridional circulation is caused by the attenuation of the GW drag, and we identified the mechanism responsible for this attenuation. Moreover, we assessed the impacts of SSW on temperatures in the equatorial region and Southern Hemisphere.
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A global view of gravity waves in the Thermosphere simulated by a general circulation model
Journal of Geophysical Research: Space Physics, 2014Co-Authors: Yasunobu Miyoshi, Hitoshi Fujiwara, Hidekatsu Jin, Hiroyuki ShinagawaAbstract:In order to study the dynamical role of gravity waves (GWs) propagating upward from the lower atmosphere to the Thermosphere, numerical simulation using a high-resolution general circulation model that contains the region from the ground surface to the exobase (about 500 km height) has been performed. Our results indicate that the zonal momentum drag due to breaking/dissipation of GWs (GW drag) plays an important role not only in the mesosphere but also in the Thermosphere. In particular, the GW drag at high latitudes in the150–250 km height region exceeds 200 ms−1 (d)−1 and is important for the zonal momentum balance. The semidiurnal variation of the GW drag is dominant in the 100–200 km height region, while the diurnal variation of the GW drag prevails above a height of 200 km. The GW drag in the Thermosphere is mainly directed against the background zonal wind, indicating the filtering effect by the background wind. A global view of the GW activity in the middle and upper atmosphere is also investigated. The global distribution of the GW activity in the Thermosphere is not uniform, and there are some enhanced regions of the GW activity. The GW activity in the Thermosphere is stronger in high latitudes than in low latitudes. The GW activity in the winter Thermosphere is influenced by the mesospheric jet and the planetary wave activity in the mesosphere.
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Gravity waves in the equatorial Thermosphere and their relation to lower atmospheric variability
Earth Planets and Space, 2009Co-Authors: Yasunobu Miyoshi, Hitoshi FujiwaraAbstract:Using a general circulation model that contains the region from the ground surface to the upper Thermosphere, we have examined characteristics of gravity waves in the equatorial Thermosphere. At an altitude of 150 km, the dominant periods of gravity waves for zonal wave number 20 (zonal wavelength λ x ≈ 2000 km), 40 (λ x ≈ 1000 km) and 80 (λ x ≈ 500 km) are 3, 1.5 and 1 h, respectively. For individual zonal wave numbers, the corresponding dominant period becomes shorter at higher altitudes due to dissipation processes in the Thermosphere, such as molecular viscosity and ion drag force, indicating that gravity waves with a larger horizontal phase velocity (larger vertical wavelength) can penetrate into the Thermosphere. The longitudinal variation of gravity wave activity in the equatorial Thermosphere and upward propagation of gravity waves from the lower atmosphere were also studied. The longitudinal distribution of gravity wave activity in the Thermosphere is quite similar to that of gravity wave activity in the lower atmosphere and the cumulus convective activity in the tropical troposphere. Our results indicate that the strong energy flux due to gravity waves from the enhanced cumulus convective activity propagates upward into the upper Thermosphere. The relation between the wind fluctuation associated with gravity waves and the ionospheric variation is discussed. Fluctuations of the neutral zonal wind with periods of 1–2 h are significant in the 200- to 300-km height region, and its amplitude sometimes exceeds 50 m s−1. These results suggest that upward propagating gravity waves can affect the ionospheric variation in the F-region.
T J Immel - One of the best experts on this subject based on the ideXlab platform.
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simulated variability of the high latitude Thermosphere induced by small scale gravity waves during a sudden stratospheric warming
Journal of Geophysical Research, 2014Co-Authors: Scott L England, Alexander S Medvedev, Erdal Yigit, T J ImmelAbstract:We present the results of the first investigation of the influence of small-scale gravity waves (GWs) originating in the lower atmosphere on the variability of the high-latitude Thermosphere during a sudden stratospheric warming (SSW). We use a general circulation model that incorporates the spectral GW parameterization of Yigit et al. (2008). During the warming, the GW penetration into the Thermosphere and resulting momentum deposition rates increase by up to a factor of 3–6 in the high-latitude Thermosphere. The associated temporal variability of GW dynamical effects at ~250 km are enhanced by up to a factor of ~10, exhibiting complex geographical variations. The peak magnitude of the GW drag temporal variability locally exceeds the mean GW drag by more than a factor of 2. The small-scale thermospheric wind variability is larger when GW propagation into the Thermosphere is allowed compared to the case when thermospheric GW effects are absent. These results suggest that GW-induced variations during SSWs constitute a significant source of high-latitude thermospheric variability.
