A climatology of medium‐scale gravity wave activity in the midlatitude/low‐latitude daytime upper thermosphere as observed by CHAMP

Park, J.; Lühr, H.; Lee, Chang-Sup; Kim, Yong Ha; Jee, Geonhwa; Kim, Jeong‐Han

doi:10.1002/2013ja019705

Cited by 72 publications

(113 citation statements)

References 44 publications

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“…Until recently, several observational studies of GWs in the T/I have been performed (e.g., Bruinsma and Forbes, 2008;Park et al, 2014;Forbes et al, 2016;Garcia et al, 2016). In particular, Park et al (2014) derived global GW distribution using CHAMP mass density and performed a first comparison with a global distribution of GW temperature variances in the stratosphere. However, in the stratosphere, only a single GW distribution at 38 km was used for comparing.…”

Section: Q T Trinh Et Al: Satellite Observations Of Vertical Couplmentioning

confidence: 99%

“…This is not sufficient to understand globally how the propagation Q. T. Trinh et al: Satellite observations of vertical coupling by gravity waves 427 and dissipation processes of GWs in the middle atmosphere influence the GW distribution in the T/I. Furthermore, the comparison in Park et al (2014) was conducted using GW temperature variance in the stratosphere, not GW momentum fluxes (GWMF). It is expected that observed GWMF are better suited for comparison than GW temperature variances because GWMF are more directly related to GW dissipation and possible excitation of secondary GWs.…”

Section: Q T Trinh Et Al: Satellite Observations Of Vertical Couplmentioning

confidence: 99%

“…Moreover, comparisons between GW distributions observed by GOCE and GW observations in the middle atmosphere were not made. Furthermore, to investigate horizontal distributions, both Park et al (2014) and Forbes et al (2016) averaged the data over several years. This can conceal the interannual variation of GW activity and is not very suitable for studying coupling processes.…”

Section: Q T Trinh Et Al: Satellite Observations Of Vertical Couplmentioning

confidence: 99%

“…Motivated by open issues remaining after Park et al (2014) and Forbes et al (2016), we analyze in our study a much larger altitude range in the middle atmosphere. In particular, long-term observations of SABER from 30 to 90 km altitude, with an altitude step of 5 km, are used.…”

Section: Q T Trinh Et Al: Satellite Observations Of Vertical Couplmentioning

confidence: 99%

“…To calculate the mass density perturbations induced by gravity waves, the smooth background density (ρ mean ) first needs to be subtracted. To define this smooth background, we apply a similar method to that of Park et al (2014). In particular, we utilize a third-order Savitzky-Golay filter with a window size of 11 data points.…”

Section: Gravity Wave Activity In the Middle Atmospherementioning

confidence: 99%

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Satellite observations of middle atmosphere–thermosphere vertical coupling by gravity waves

et al. 2018

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Abstract. Atmospheric gravity waves (GWs) are essential for the dynamics of the middle atmosphere. Recent studies have shown that these waves are also important for the thermosphere/ionosphere (T/I) system. Via vertical coupling, GWs can significantly influence the mean state of the T/I system. However, the penetration of GWs into the T/I system is not fully understood in modeling as well as observations. In the current study, we analyze the correlation between GW momentum fluxes observed in the middle atmosphere (30-90 km) and GW-induced perturbations in the T/I. In the middle atmosphere, GW momentum fluxes are derived from temperature observations of the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) satellite instrument. In the T/I, GW-induced perturbations are derived from neutral density measured by instruments on the Gravity field and Ocean Circulation Explorer (GOCE) and CHAllenging Minisatellite Payload (CHAMP) satellites. We find generally positive correlations between horizontal distributions at low altitudes (i.e., below 90 km) and horizontal distributions of GW-induced density fluctuations in the T/I (at 200 km and above). Two coupling mechanisms are likely responsible for these positive correlations: (1) fast GWs generated in the troposphere and lower stratosphere can propagate directly to the T/I and (2) primary GWs with their origins in the lower atmosphere dissipate while propagating upwards and generate secondary GWs, which then penetrate up to the T/I and maintain the spatial patterns of GW distributions in the lower atmosphere. The mountain-wave related hotspot over the Andes and Antarctic Peninsula is found clearly in observations of all instruments used in our analysis. Latitude-longitude variations in the summer midlatitudes are also found in observations of all instruments. These variations and strong positive correlations in the summer midlatitudes suggest that GWs with origins related to convection also propagate up to the T/I. Different processes which likely influence the vertical coupling are GW dissipation, possible generation of secondary GWs, and horizontal propagation of GWs. Limitations of the observations as well as of our research approach are discussed.

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Section: Q T Trinh Et Al: Satellite Observations Of Vertical Couplmentioning

confidence: 99%

Section: Q T Trinh Et Al: Satellite Observations Of Vertical Couplmentioning

confidence: 99%

Section: Q T Trinh Et Al: Satellite Observations Of Vertical Couplmentioning

confidence: 99%

Section: Q T Trinh Et Al: Satellite Observations Of Vertical Couplmentioning

confidence: 99%

Section: Gravity Wave Activity In the Middle Atmospherementioning

confidence: 99%

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Satellite observations of middle atmosphere–thermosphere vertical coupling by gravity waves

et al. 2018

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Ionospheric Characteristics and Models

Goodman

2016

Wiley Encyclopedia of Electrical and Electronics Engineering

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The ionized region roughly between 60 and 1200 km above the earth's surface is generally referred to as the ionosphere, even though some ionization persists above and below these bounds. Since most practical problems relate to the free electron number density N e , it is convenient to specify a restricted altitude regime since many legacy systems such as LEO satellite and HF communications, HFDF (i.e., direction finding), and surveillance systems such as OTHR (over‐the‐horizon radar) depend upon this restricted region in a substantive way. But there are other applications to be considered. For example, exoionospheric electrons will augment the ionospheric total electron content (TEC) encountered by GNSS signal waveforms and will introduce additional group path delay errors if compensation schema are not introduced. As a result, many ionospheric models include the plasmaspheric contribution to the TEC. This article examines basic theory of the ionosphere, but much of the material details ionospheric structure, ranging from kilometer‐scale variations causing scintillation or spread‐F to the mesoscale features associated with electrodynamic forces, an imbedded geomagnetic field and upper atmospheric wind patterns. We look at these structures in both space and time for pertinent geographic regions, and identify relationships with solar–terrestrial physics, or space weather phenomena in the more modern vernacular. We examine traveling ionospheric disturbances (TID), an ionospheric tracer of atmospheric gravity waves (AGW), their properties, and their possible sources. Fundamental properties of the more relevant ionospheric models are identified and details are referenced. We cover real‐time forecasting and novel data assimilation schemes. We conclude with a section on challenges facing the ionospheric specialist.

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Limb sounders tracking topographic gravity wave activity from the stratosphere to the ionosphere around midlatitude Andes

et al. 2015

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Several studies have shown that the surroundings of the highest Andes mountains at midlatitudes in the Southern Hemisphere exhibit gravity waves (GWs) generated by diverse sources which may traverse the troposphere and then penetrate the upper layers if conditions are favorable. There is a specific latitude band where that mountain range is nearly perfectly aligned with the north‐south direction, which favors the generation of wavefronts parallel to this orientation. This fact may allow an optimization of procedures to identify topographic GW in some of the observations. We analyze data per season to the east and west of these Andes latitudes to find possible significant differences in GW activity between both sectors. GW effects generated by topography and convection are expected essentially on the eastern side. We use satellite data from two different limb sounding methods: the Global Positioning System radio occultation (RO) technique and the Sounding of the Atmosphere using Broadband Emission Radiometry instrument, which are complementary with respect to the height intervals, in order to study the effects of GW from the stratosphere to the ionosphere. Activity becomes quantified by the GW average potential energy in the stratosphere and mesosphere and by the electron density variance content in the ionosphere. Consistent larger GW activity on the eastern sector is observed from the stratosphere to the ionosphere (night values). However, this fact remains statistically significant at the 90% significance level only during winter, when GWs generated by topography dominate the eastern sector. On the contrary, it is usually assumed that orographic GWs have nearly zero horizontal phase speed and will therefore probably be filtered at some height in the neutral atmosphere. However, this scheme relies on the assumption that the wind is uniform and constant. Our results also suggest that it is advisable to separate night and day cases to study GWs in the ionosphere, as it is more difficult to find significant statistical differences during daytime. This may happen because perturbations induced by GWs during daytime are more likely to occur in a disturbed environment that may hinder the identification of the waves.

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A climatology of medium‐scale gravity wave activity in the midlatitude/low‐latitude daytime upper thermosphere as observed by CHAMP

Cited by 72 publications

References 44 publications

Satellite observations of middle atmosphere–thermosphere vertical coupling by gravity waves

Satellite observations of middle atmosphere–thermosphere vertical coupling by gravity waves

Ionospheric Characteristics and Models

Limb sounders tracking topographic gravity wave activity from the stratosphere to the ionosphere around midlatitude Andes

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