The neutral wind system in the thermosphere simu- lated by using KUGCM indicates the following: (1) 2- to 20-day waves, including planetary and Kelvin waves, dissipate rapidly above about 125 km, and 0.5- to 3-h waves become predominant with increasing altitude beyond 100 km, (2) zonal winds above 200 km altitude are, on the whole, eastward after local sunset (∼1900 LT) until sunrise (∼0600 LT), (3) zonal wind patterns due to AGWs with pe- riods of 1–4 h above 120 km altitude exhibit wavy structures with scale lengths of about 30–1000 km and, as a whole, move eastward at about 100 − 1 while changing the structures with time. The wind direction changes within such scale lengths. The wavy structures change day by day. These simulation results suggest that short-period gravity waves, which may contribute to the seeding of the RT instability generating plasma bubbles accompanied by scintillations, are generally present above 120 km altitude and that the background conditions necessary for the RT instability are modulated by planetary-scale atmospheric waves. We sup- pose that such a scenario can explain the day-to-day vari- ability in the scintillation occurrences. Future work should investigate how ionospheric electric ﬁelds, electron density distribution, etc. are modulated with time, day and season by the simulated neutral winds.
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After the M 9.0 Tohoku Earthquake (epicenter: 38.32 ◦ N, 142.36 ◦ E, origin time: 05:46:23 UT on March 11, 2011 (US Geological Survey)), two-dimensional structures of pe- riodic oscillations of TEC were observed by a dense GPS receiver network (Chen et al., 2011; Saito et al., 2011; Tsugawa et al., 2011). The TEC oscillations had circu- lar or concentric structures. The center of the structures was closer to the Japan trench than the epicenter (Tsugawa et al., 2011). This was consistent with the source of the largest tsunami estimated from tsunami waveform inver- sion (Fujii et al., 2011). This indicates that the atmospheric waves were generated by a displacement of the sea surface caused by the earthquake, and propagated upward to the thermosphere (Saito et al., 2011; Tsugawa et al., 2011). In the vicinity of the epicenter, two-dimensional structures of the ionospheric variations generated by the acoustic reso- nance between the ground surface and the lower thermo- sphere was ﬁrstly observed (Saito et al., 2011). The area of the acoustic resonance may correspond to that of the sea-surface displacement. This means that the area and the amplitude of the sea-surface displacement can be estimated from those of the observed TEC oscillations. It is necessary for the estimation to simulate the structures of the oscilla- tions qualitatively and quantitatively. In this study, as a ﬁrst step for the estimation, we simulate qualitatively the neutral atmospheric perturbations at the ionospheric heights.
Using GPS/MET (meteorology) radio occultation, Hocke and Tsuda (2001) investigated the longitudinal distributions of gravity wave activity in the stratosphere and E -region plasma irregularities (80- to 120-km heights). The E -region plasma irregularities are probably generated by atmospheric waves of the neutral atmosphere through the ion-neutral coupling process. As such, they clearly demonstrated that the longitudinal distribution of plasma irregularities in the MLT region was similar to that of the water vapor pressure in the tropics, indicating the dynamical coupling between the troposphere and the MLT region through the upward propagation of gravity waves. However, the longitudinal distribution of gravity wave activity above the MLT region and its relation to plasma irregularities in the F-region are not known. Therefore, in our study, we used a GCM that contains the region from the ground surface to the upper thermosphere to investigate the behavior of gravity waves in the equatorial thermosphere and the upward propagation of gravity waves from the lower atmosphere to the upper thermosphere. We focused our attention on the longitudi- nal variation in gravity wave activity in the equatorial ther- mosphere and its relation with the cumulus convection in the tropical troposphere. As mentioned above, ﬂuctuations of the wind due to gravity waves in the thermosphere in- ﬂuence the variability of the ionospheric parameters (e.g., Hocke and Schlegel, 1996). Here, we discuss the wind ﬂuc- tuation associated with gravity waves in the thermosphere and its relation to ionospheric variability. The descriptions of the GCM used in this study and the numerical simula- tion are presented in Section 2. The results and discussion are presented in Sections 3 and 4, respectively. A summary follows in Section 5.
Press, 1955; Garrett, 1970), tsunami waves recorded at far- field sites originated from coupling between the ocean sur- face and the explosion-induced atmospheric waves (that cir- cuited the globe three times – see Murty, 1977) rather than from direct water waves propagated from the source area (Fig. 15). The problem is the mismatch in time between ob- served and expected tsunami waves: the waves in the Pacific and Atlantic were recorded too early for long ocean waves to arrive at these sites but in good agreement with atmospheric sound waves (U ∼ 340 m/s) to arrive (Garrett, 1970). There- fore, the near-field records of the 1883 Krakatau tsunami were apparently related to real surface ocean waves arriving from the source area whereas the records from intermediately located tide gauges included some mixture of directly arriv- ing ocean waves and atmospherically-generated waves. Far- field records were associated purely with atmospheric waves. From an orthodox point of view, the term “tsunami” cannot even be used for the latter. However, it is much easier to call all these waves “tsunamis”, keeping in mind the actual generation mechanism of these waves. Certainly, we do not consider this example as a major argument; this event was exceptional and most of meteorological tsunamis have noth- ing to do with any seismic or volcanic activity. Nevertheless, this example clearly indicates the very close relationship be- tween tsunamis and meteotsunamis.
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mooring included a sequence of temperature loggers posi- tioned at 2.3, 5, 8, 11.3, 14, 17, 20.3 and 23 m above the sea floor (bottom depth ∼25.2 m). The inclusion of a subsurface buoy insured buoyancy reduced cable movement induced by currents. Overall, the water column was well mixed during the late fall and winter (November to February) and stratified in late spring and summer (May to August). High-frequency temperature oscillations were detected when the water col- umn was stratified and appeared restricted to the lower part of the water column. Figure 6 shows a typical temperature sec- tion obtained in the study site (22 August 2009). No evidence of a strong oceanic internal wave field has been found from observations taken from the shelf edge. This result reinforces the idea that not only winter period observations (Fig. 4a) should be of atmospheric waves since there is no stratifica- tion in the ocean to sustain internal waves, but also summer large scale observations may be of atmospheric nature. We stress that the high-frequency oscillations in Fig. 6 have pe- riods of the order of 5 min whilst the satellite observations of internal waves within this area typically have wavelengths (average distance from crest to crest) of 10 km. If these sig- natures were to be oceanic they would have phase speeds of the order of 30 m s −1 , which is not a realistic value for oceanic internal waves.
Non-hydrostatic models are useful for direct numerical simulations of waves and turbulence in the atmosphere. For example, Baker and Schubert (2000) simulated non- linear AGWs in the atmosphere of Venus. They modeled waves in the atmospheric region with horizontal and ver- tical dimensions of 120 and 48 km, respectively. Fritts and Garten (1996), also Andreassen et al. (1998) and Fritts et al. (2009, 2011), simulated the instabilities of Kelvin and Helmholtz and turbulence produced by breaking atmospheric waves. These models simulate turbulence and waves in atmo- spheric regions with limited vertical and horizontal dimen- sions. The models exploited spectral methods and Galerkin- type series for converting partial differential equations (ver- sus time) into the ordinary differential equations for the spec- tral series components. Yu and Hickey (2007) and Liu et al. (2008) developed two-dimensional numerical models of atmospheric AGWs.
In this study, we use the data of observations of atmo- spheric pressure variations in 2016 obtained on four mi- crobarographs of the A.M. Obukhov Institute of Atmo- spheric Physics, RAS. All microbarographs are located in the Moscow region; the points are at Moscow State University, MosRentgen, the A.M. Obukhov Institute of Atmospheric Physics, RAS, and Zvenigorod Research Station (ZRS) of the A.M. Obukhov Institute of Atmospheric Physics, RAS, Fig. 1 (Kulichkov et al., 2017). The microbarographs record varia- tions in atmospheric pressure in the frequency range from 10 −4 to 3 Hz. We process the data for 2016 and highlight the cases when the amplitude of pressure variations significantly exceeded the background variations. At some moments on 17–18 July 2016, the amplitude of pressure variations ex- ceeded the average 30 times. To perform numerical simu- lations, we take pressure variation data for 17–18 July 2016. Below we present the results of simulations of the prop- agation of atmospheric waves from surface pressure varia- tions obtained from observational data. No similar simula-
A real 3-D tomographic retrieval combining different limb-scanning sequences requires a large number of tangent points in the target atmospheric volume. In the case of an airborne platform, this can be realized by viewing the target volume from different directions, for example by perform- ing closed flight patterns that enclose the target volume, or by panning the viewing direction of the instrument during flight. Such an observation scenario was suggested by Unger- mann et al. (2011) and applied by Kaufmann et al. (2015) and Krisch et al. (2017) for an airborne infrared limb sounder. For a spaceborne platform, the feasibility of resolving fine GW structures with tomographic retrievals has been demon- strated using simulated measurements of PREMIER mis- sion (Process Exploration through Measurements of Infrared and millimetre-wave Emitted Radiation; Ungermann et al., 2010). The PREMIER concept is based on infrared limb imaging (Riese et al., 2005), which provides high along-track sampling ( ∼ 50 km) and across-track sampling ( ∼ 25 km) at the same time by combining novel two-dimensional detector arrays with Fourier spectroscopy (e.g., Friedl-Vallon et al., 2014).
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Chaos phenomena and chaotic systems have been extensively studied by many researchers due to their various applications in the ﬁelds of atmospheric dynamics, population dy- namics, electric circuits, cryptology, ﬂuid dynamics, lasers, engineering, stock exchanges, chemical reactions, and so on [–]. Most of the complex dynamical phenomena are char- acterized by chaotic and hyperchaotic systems of nonlinear ordinary diﬀerential equations [–].
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At remote distances from the epicenter, Rayleigh waves are the most important source of coseismic infrasound because they propagate along Earth’s surface without significant attenuation of the amplitude due to geomet- rical spreading (Lay and Wallace 1995). The ionospheric anomaly exhibits a characteristic of traveling ionospheric disturbances following the Rayleigh wave propagation (Liu and Sun 2011; Maruyama et al. 2012). Short-period Rayleigh waves in the range of 15–50 s, near the Airy phase, yield ionospheric density fluctuations with verti- cal wavelengths of 7.5–50 km, because the sound speed is 500–1000 m/s at ionospheric heights. The vertical wavelength is less than the bottom-half thickness of the ionosphere, and several cycles of alternating enhance- ments and depletions of electron density cause distortion of the ionograms characterized as a multiple cusp signa- ture (MCS) (Maruyama et al. 2011, 2016a, b; Maruyama and Shinagawa 2014). Each cusp is related to a density ledge, and the vertical separation of the ledges is the wavelength of the infrasound propagating in the thermo- sphere (Maruyama et al. 2012, 2016a). Thus, MCS iono- grams are considered to be a wave snapshot. Note that this type of ionospheric anomaly is not detected by TEC measurement because the alternating enhancements and depletions of electron density along the ray path offset the contribution to the TEC changes.
AGW observations in the lower atmosphere, in particular in the atmospheric boundary layer (ABL), are based mostly on fixed-point or mobile platform pressure measurements (Román-Cascón et al., 2015; Sun et al., 2015). For study- ing AGW, coherent Doppler wind lidars (CDWLs) and so- dars are used as well. Newsom and Banta (2003) and Wang et al. (2013) applied 2 µm CDWL to investigate of low-level jet and gravity waves in the stable ABL over flat and urban terrains, respectively. Lyulyukin et al. (2015) observed AGW in the lower atmospheric layer (300–400 m) based on sodar data. However, the data of lidar and sodar observations of AGW in the ABL are few and far between.
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Research completed during the past 20 years has not yet yielded full understanding of all the factors which appear to be involved in m olecular absorption. For example, in a recent critical review , G rant observed th a t since 1969, a t least 13 m easurem ents of w ater vapour absorption coefficients in the 8 - 1 3 pm spectral region have been made. G rant noted considerable disparity between the different w ater vapour continuum data sets. A greem ent betw een experim ent and num erical sim ulation based on theory is not good. T his m akes assessm ent and prediction of the effects of absorption on an atmospheric waveguide difficult. W herever possible, a range of values of effective absorption coefficients for CO 2 laser radiation will be used, based on an
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The GPS meteorological analysis detected asymmetric non-linear atmospheric structure which may suggest atmo- spheric mountain lee waves excited by a strong westerly wind ahead of an approaching cold front on 7th March 1997, as evidenced by significant atmospheric gradients are detected by GPS data analysis and numerical atmospheric model. According to the analysis, the result from the sites along the east coast of the Izu Peninsula indicates a wet and cold atmosphere to the west of these sites. On the contrary, the island site 6 km east of the east coast detects a strong gradient to the east of the island. Cloud images of the region indicate rows of the clouds due to mountain lee waves con- sistent with the GPS measurements. A numerical simulation explains the mountain lee waves. The atmospheric inhomo- geneity induces large systematic errors in the site horizon- tal estimates from the processing without the atmospheric horizontal gradient estimations, and the analysis including the simple gradient perturbed atmospheric model still re- tains some of the systematic errors. This study assigns that the large errors in position estimates can result from atmo- spheric phenomena like mountain lee waves in regions with mountainous topography like the Japanese Islands.
There have been reported rather a large number of obser- vational facts in support of the 2nd channel, mainly based on subionospheric VLF/LF propagation data. Molchanov and Hayakawa (1998) studied the terminator times in VLF sig- nal, and found that the modulation of 2, 5, and 10 days (the frequency range of atmospheric planetary waves) is greatly enhanced before an EQ. This finding has led us to con- clude that atmospheric oscillations might be involved in this lithosphere-ionosphere coupling. Terminator time (either morning or evening) (Hayakawa et al., 1996) appears once a day, so that the harmonic analysis of terminator times enables us to study the modulation with the order of days. Then, higher frequency modulations have been studied on the ba- sis of nighttime data in subionospheric VLF/LF data. Miyaki et al. (2002) found, for the first time, the enhancements in the VLF fluctuation spectrum in the frequency range of at- mospheric gravity waves (AGWs) (the period of 10 min to 1 h), which are well correlated with EQs. Later, Rozhnoi et al. (2004), Shvets et al. (2004), Hayakawa et al. (2005), Horie et al. (2007a), and Rozhnoi et al. (2007a, b) have provided more evidences on the importance of AGW effects, and recently Horie et al. (2007b) have obtained a very con- vincing direct evidence of wave-like structures in the case of Sumatra EQ as a strong support of the AGW effects. Further additional supports have been recently publishied by Muto et al. (2009), Korepanov et al. (2009), and Blaunstein and Hayakawa (2009). These would lend us a further support to the 2nd channel as the lithosphere-ionosphere coupling.
In this paper modiﬁed theory of cyclotron damping of ion whistler wave is discussed in which thermal effects are taken into account explicitly and the results are used to explain the sudden cut-off of the wave amplitude. It is also pointed out that in this procedure a better estimate of ion tempera- ture is also possible. The ion cyclotron wave propagating through plasma containing different ions interacts with the energetic ions when the Doppler-shifted wave frequency be- comes equal to the ion cyclotron frequency. During the in- teraction process energy exchange takes place. In the case of Maxwellian isotropic velocity distribution function of ions, the exchange of energy takes place from waves to the ions and the wave amplitude is attenuated. Considering temporal and spatial damping, time development of wave amplitude has been studied. Considering model ionosphere numerical computations are presented.
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The study results also had limitations. The daily mortality of the elderly was affected by many factors besides temperature, such as the change in the characteristics of popu- lations, medical conditions, the change of healthy behavior, and other individual fac- tors. These confounding factors were not taken into account in the model because of the lack of data. More impact factors should be subject to analysis with a view to iden- tify the causes underlying the increased mortality among the elderly during heat waves in the future.
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There have been many recent observations of torsional mo- tions recently observed in the solar photosphere, at the very limits of modern telescopes. Modelling these motions which have the potential to be ubiquitous in the photosphere, demon- strates the potential for large amounts of Alfvén wave excita- tion in small scale magnetic structures. Also shown via the numerical simulations in this work is the damping and propa- gation properties of the excited MHD waves at various heights in a realistic expanding magnetic flux tube. Further extensions of this work into the transition region and corona would allow more, indirect, comparison to observational results of heating in the transition region.
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This study reports on observations of atmospheric gravity waves/traveling ionospheric disturbances (AGWs/TIDs) using Global Positioning System (GPS) total electron content (TEC) and Fabry-Perot Interferometer’s (FPI) in- tensity of oxygen red line emission at 630 nm measurements over Svalbard on the night of 6 January 2014. TEC TIDs have primary periods ranging between 29 and 65 minutes and propagate at a mean horizontal velocity of ∼749-761 m/s with azimuth of ∼345 ◦ -347 ◦ (which corresponds to poleward propagation
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There have been many studies of the effects of processes in space on the ionosphere and atmosphere. Examples in- clude tidal effects, energetic particle precipitation, the gen- eration of acoustic-gravity waves by current systems, ef- fects of the current systems on geomagnetically-induced currents (GIC), and the inﬂuence of radiation on the chem- istry of the ionosphere. The inﬂuence of atmospheric pro- cesses on the magnetosphere has received much less atten- tion in the literature. Previous studies have discussed the electromagnetic radiation of lightning discharges, and there are indications of magnetospheric manifestations of earth- quakes.
diffusion and a decadal growth rate, but its extremely long period (about a hundred years), while probably irrelevant for decadal processes, is clearly of importance in the interpretation of long climate model runs using a simplified atmosphere. The shape of the unstable mode resemble that of a first mode (no zero-crossings in the vertical). This means that the unstable mode found when an atmospheric EBM is coupled to a continuously stratified ocean is not negligible in those parameter settings and could be found with a simpler ocean of fewer layers. Also, its existence has been tested within an initial value problem which proved its growing behaviour. The sensitivity of the unstable mode to the different parameters taken into ac- count is thoroughly explored. The background stratification has been modified, an homogeneous mixed layer has been included at the surface and a possible range of the coefficient of air-sea exchange λ was used without successfully destroying the instability. Moreover, as K v seemed to be the main factor in controlling the vertical
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