First three dimensional wave characteristics in the daytime upper atmosphere derived from ground‐based multiwavelength oxygen dayglow emission measurements

Pallamraju, Duggirala; Karan, Deepak K.; Phadke, Kedar A.

doi:10.1002/2016gl069074

Cited by 19 publications

(30 citation statements)

References 44 publications

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“…Ground-based airglow emission measurements yield column integrated values; however, as they emanate from a finite thickness, they retain the information of fluctuations of smaller timescales as the reactants responsible for the airglow emissions do get affected by the passage of any wave-like fluctuations in the medium (e.g., Karan & Pallamraju, 2017, 2018Laskar et al, 2015;Pallamraju et al, 2010Pallamraju et al, , 2014Pallamraju et al, , 2016. Conventionally, established method for deriving GW periodicities, scale sizes, and propagation speeds has been through the analysis of temporal variation in optical airglow emission intensities.…”

Section: Discussionmentioning

confidence: 99%

“…We have analyzed the GW characteristics at each of the common time periods present at all the height variations of isoelectron density contours. Such a method was successfully used in an earlier study to obtain the first three-dimensional GW characteristics in the daytime through optical measurement technique (e.g., Pallamraju et al, 2016). In order to do that, only the power corresponding to a particular dominant time period (power spectral density, PSD > FAL) is considered by using a band-pass filter with a width of peak time period ± Brunt-Väisälä time period of 0.25 hr (Brunt-Väisälä frequency, N = (2g*/5H) 1/2 ; Shiokawa et al, 2009, where H is the neutral scale height [an average value of 54 km is considered for this duration] and g* is the acceleration due to gravity at a particular altitude), while the powers of the rest of the spectra are equated to zero.…”

Section: Estimation Of Vertical Phase Speeds (C Z ) Of Gw Propagationmentioning

confidence: 99%

“…In addition to airglow intensities, some of the optical measurements can yield information on the variation of temperatures, and winds, which also have been used to obtain information on GW characteristics. While GW periodicities can be obtained from a single point measurement (e.g., Chakrabarty et al, 2008;Pallam Raju et al, 1996), large field-of-view optical measurements are required for deriving information on scale sizes and propagation directions of the GWs (e.g., Karan & Pallamraju, 2017, 2018Lakshmi Narayanan et al, 2010;Pallamraju et al, 2013Pallamraju et al, , 2014Pallamraju et al, , 2016Shiokawa et al, 2009).…”

Section: 1029/2019ja026723mentioning

confidence: 99%

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On Deriving Gravity Wave Characteristics in the Daytime Upper Atmosphere Using Radio Technique

et al. 2019

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The importance of neutral wave dynamics in the understanding of the upper atmospheric processes is well known. Conventionally, optical methods are used to derive information on the neutral wave dynamics by obtaining gravity wave (GW) characteristics. Optical measurement techniques use airglow emissions as tracers to obtain such information that correspond to altitudes from where the emissions emanate. However, in this paper, we describe a method using radio wave measurement technique (digisonde) to obtain information on the neutral GW behavior. It involves monitoring of variations in the heights of isoelectron densities as a function of time, and their phase shifts, if any, to derive vertical propagation speeds and scale sizes of GWs. The daytime values of GW time periods, vertical phase speeds, and vertical scale sizes obtained for the duration of 16–21 May 2015 are in the range of 1.47 ± 0.05 to 2.64 ± 0.07 hr, 30.06 ± 4.35 to 45.69 ± 11.84 m/s, and 183.21 ± 39.23 to 393.07 ± 66.38 km, respectively. Further, we have used the GW dispersion relation to make a first‐order estimation of the horizontal scale sizes. This method of deriving neutral GW characteristics through radio measurement technique is effective for the daytime conditions and opens up new possibilities of investigations of the wave dynamical behavior in the upper atmosphere during all weather conditions.

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Section: Discussionmentioning

confidence: 99%

Section: Estimation Of Vertical Phase Speeds (C Z ) Of Gw Propagationmentioning

confidence: 99%

Section: 1029/2019ja026723mentioning

confidence: 99%

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On Deriving Gravity Wave Characteristics in the Daytime Upper Atmosphere Using Radio Technique

et al. 2019

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“…Such a selective filtering, but in one dimension, was successfully used to track the oscillations of a given gravity wave time period (Pallamraju et al, 2016) in the daytime airglow emissions to obtain information on three-dimensional gravity wave behavior in the daytime. The data sets over a station (altitude profile vs. time evolution, 2-D data) are Fourier transformed to the vertical-wave number and frequency domain, from which the tidal and zero-frequency oscillations were then filtered out (wave number-frequency band removed) to obtain the residuals.…”

Section: Wave Analysesmentioning

confidence: 99%

“…Interested readers can see supporting information Figure S1, which shows an example of the frequency selection. Such a selective filtering, but in one dimension, was successfully used to track the oscillations of a given gravity wave time period (Pallamraju et al, 2016) in the daytime airglow emissions to obtain information on three-dimensional gravity wave behavior in the daytime. The band removal filtering was applied for all wave numbers (vertical) within the temporal frequency bands, specific details of which are given in section 3.…”

Section: Wave Analysesmentioning

confidence: 99%

Interhemispheric Meridional Circulation During Sudden Stratospheric Warming

Laskar

McCormack²,

Chau

et al. 2019

JGR Space Physics

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Although sudden stratospheric warming (SSW) is mainly a northern high‐latitude phenomena, there are several reports of a concomitant global dynamical response throughout the mesosphere and lower thermosphere. Published reports based on model simulations so far attributed such variabilities to changes in global circulation; however, there is no clear explanation of how all these regions are physically connected during SSW events. The present investigation uses wind observations from two ground‐based specular meteor radars over northern high latitudes and midlatitudes and global winds from a high‐altitude meteorological analysis system to characterize global mesospheric circulation anomalies for major SSW events during 2010 and 2013. During these events radar observations and the reanalysis winds exhibited strong southward winds over the two northern midlatitude and high‐latitude stations. By removing seasonal variability from the high‐altitude meteorological analyses, we show that these southward wind anomalies are indeed part of a larger global‐scale circulation, which gets set up during SSW and extend from the Northern pole to low‐latitude regions of Southern Hemisphere in the mesosphere and lower thermosphere altitudes. These results also offer a possible explanation of how low‐latitude ionospheric electrodynamics are influenced by the changes in the circulation set in during SSW at high latitudes.

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Small‐scale longitudinal variations in the daytime equatorial thermospheric wave dynamics as inferred from oxygen dayglow emissions

Karan

Pallamraju

2017

JGR Space Physics

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The equatorial upper atmospheric dynamic processes show both latitudinal and longitudinal variabilities. While the variability in latitudes can exist over small distances (approximately hundreds of kilometers), the longitudinal behavior has been shown to be existing mainly over large spatial separations (approximately thousands of kilometers). In the present work we have used variations in thermospheric optical dayglow emissions at OI 557.7, 630.0, and 777.4 nm, as tracers of neutral dynamics. These emissions are obtained simultaneously from a high‐resolution slit spectrograph, Multi wavelength Imaging Spectrograph using Echelle grating, from a low‐latitude location, Hyderabad (17.5°N, 78.4°E; 8.9°N magnetic latitude) in India, to investigate the longitudinal differences in the upper atmospheric processes over short separations. Spectral analyses of gravity waves carried out on the dayglow emission intensity variations for different independent viewing directions on some days show dissimilar periodicities suggesting the existence of longitudinal differences. Gravity wave scale sizes and the propagation characteristics on these days are different from those in which longitudinal differences are not seen. Further, the zenith diurnal emission intensity patterns are different on the days with and without the observed longitudinal variability. This work shows for the first time that longitudinal differences in upper atmospheric processes can exist at even as small as 3° longitude separations. Such longitudinal differences seen in the neutral dayglow emission intensities are attributed to the zonal variation in the daytime equatorial electrodynamics.

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First three dimensional wave characteristics in the daytime upper atmosphere derived from ground‐based multiwavelength oxygen dayglow emission measurements

Cited by 19 publications

References 44 publications

On Deriving Gravity Wave Characteristics in the Daytime Upper Atmosphere Using Radio Technique

On Deriving Gravity Wave Characteristics in the Daytime Upper Atmosphere Using Radio Technique

Interhemispheric Meridional Circulation During Sudden Stratospheric Warming

Small‐scale longitudinal variations in the daytime equatorial thermospheric wave dynamics as inferred from oxygen dayglow emissions

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