Global distribution of neutral wind shear associated with sporadic <i>E</i> layers derived from GAIA

Shinagawa, Hiroyuki; Miyoshi, Y.; Jin, Hidekatsu; Fujiwara, Hitoshi

doi:10.1002/2016ja023778

Cited by 62 publications

(76 citation statements)

References 56 publications

(120 reference statements)

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“…Li et al () showed the effect of ENSO on gravity wave activity and related changes to the background atmosphere in the MLT. Combining these results with those of Shinagawa et al (), we attempt to deduce whether an ENSO modulation on the background atmosphere between 90 and 110 km would be consistent with our COSMIC observations on the ENSO modulation of E s . Li et al () actually focus during Boreal winter.…”

Section: Discussionsupporting

confidence: 57%

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On the Relationship Between E Region Scintillation and ENSO Observed by FORMOSAT‐3/COSMIC

et al. 2018

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Global Navigation Satellite System radio occultation signals often show extremely strong levels of scintillation when passing through the ionospheric E region. This is related to sporadic E (Es)-dense layers of metallic ions that can form in the E region, influencing terrestrial and satellite radio propagation. In our report on the 2007-2014 variation of E region S4 amplitude fluctuation indices measured by the FORMOSAT-3/Constellation Observing System for Meteorology Ionosphere and Climate (COSMIC) satellite constellation, we find that the spatial and temporal variation of the maximum S4 index in the E region is proportionate to the occurrence rate of extreme scintillation and by extension, sporadic E. We also find that the monthly median extreme S4 amplitude fluctuation index in the E region midlatitudes shows a dependence on variation of the El Niño-Southern Oscillation (ENSO) in the troposphere that has not been previously reported. The ENSO-related variation of the E region median extreme S4 indices varies closely with the tropopause height, with both parameters lagging the Oceanic Niño Index by roughly 1 to 2 months, while also displaying a similar spectrum of periodicities. This similarity is especially strong in the southern midlatitudes. These results indicate that ENSO signatures can be transmitted to Es formation mechanisms, potentially through modulation of vertically propagating atmospheric tides that alter lower thermospheric wind shears. The end result is the modulation of the interannual variation of extreme Es values by ENSO.Plain Language Summary Global Navigation Satellite System signals often become extremely unstable when passing through altitudes between approximately 90 and 110 km. This is related to dense layers of metallic ions deposited by meteors burning up in the atmosphere, known as sporadic E (Es). In our observations of the fluctuation of Global Navigation Satellite System signals passing through this region measured by the FORMOSAT-3/Constellation Observing System for Meteorology Ionosphere and Climate satellite constellation, we find that the level of signal fluctuation shows a dependence on variation of the El Niño-Southern Oscillation (ENSO) in the troposphere that has not been previously reported. A similar ENSO-related variation is also observed in the height of the tropopause between 10 and 20 km, showing that ENSO can affect atmospheric phenomena that are capable of propagating upward to altitudes where Es occurs. This result illustrates a vertical connection in the atmosphere that has not been previously observed.

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Section: Discussionsupporting

confidence: 57%

“…This study utilizes S 4 indices between 90 and 110 km. This region is known to exhibit significant variations in vertical wind shear due to both the general circulation and a wide spectrum of atmospheric waves particularly atmospheric tides (Shinagawa et al, ).…”

Section: Discussionmentioning

confidence: 99%

On the Relationship Between E Region Scintillation and ENSO Observed by FORMOSAT‐3/COSMIC

et al. 2018

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“…Chu et al 15 (2014) employed the COSMIC measurements to study the global morphology of E s OR and the result of theoretical simulations suggested that the E s OR seasonal variation is likely attributed to the convergence of metallic ion flux caused by the vertical wind shear. Shinagawa et al (2017) calculated the global distribution of the vertical ion convergence and showed that the local and seasonal variations in the wind shear distribution could partially account for the geographical and seasonal variation of E s OR. 20 There have been a lot of papers reporting the geographical distribution and seasonal variation of global E s layers retrieved from GPS RO signals, and nearly all these works were on the occurrence rate of E s layers.…”

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confidence: 99%

The global climatology of the intensity of ionospheric sporadic <i>E</i> layer

Yu¹,

Xue²,

Yue³

et al. 2018

Preprint

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On the basis of S4max data retrieved from COSMIC GPS radio occultation measurements, the long-term climatology of the intensity of E s layers is investigated for the period from December 2006 to January 2014. The global maps of E s intensity shows a high spatial resolution geographical distributions and strong seasonal dependence of E s layers.The maximum intensity of E s occurs in the midlatitudes, and its value in summer is 2-3 times larger than that in winter. A relatively strong E s layer is observed at the North and South Poles with a distinct boundary dividing the middle latitudes and high latitudes along 60 • -5 80 • geomagnetic latitude bands. Besides, simulation results shows that the convergence of vertical ion velocity could partially explain the seasonal dependence of E s intensity. Furthermore, some disagreements between the distributions of calculated divergence of vertical ion velocity and observed E s intensity indicate that other processes such as magnetic field effects, meteoric mass influx into the earth's atmosphere and chemical processes of metallic ions should also be considered, which play an important role in the spatial and seasonal variations of E s layers. 10 1 IntroductionThe ionospheric sporadic E (E s ) layers are known as thin-layered structures of intense high electron density at 90-130 km altitudes. Rocket-borne mass spectrometric measurements proved that the E s layer is mostly the ionization of metal atoms such as Fe + , Mg + , and Na + (Kopp, 1997;Grebowsky and Aikin, 2002). The E s layer is mainly at midlatitudes and relatively absent at geomagnetic equator and high latitudes (Whitehead, 1989). It is widely accepted that the mechanism responsible for the E s 15 layer formation at midlatitudes is the windshear theory, in which the zonal and meridional winds provide the vertical windshear convergence nodes. As a result, the long-lived metallic ions are forced to converge towards the wind shear null to form a thin layer of intense metallic ionization (Whitehead, 1961;Macleod, 1966;Whitehead, 1970;Nygren et al., 1984;Whitehead, 1989;Haldoupis, 2012). In the equatoral region, the physical process of E s irregularities is attributed to the gradient-drift instabilities associated with the equatorial electrojet (Tsunoda, 2008). The E s layer generally has a vertical scale of 1 km or less, but its 20 1 Atmos. Chem. Phys. Discuss., https://doi.

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“…They found that wind shear theory satisfactorily explains the summer Es maximum, although their metallic ion distribution also maximises in summer, which is broadly in correspondence with qualitative results by Haldoupis et al (2007) who compared meteor rates with Es occurrence rates (OR). Shinagawa et al (2017) analyzed the global distribution of vertical ion convergence based on GAIA Earth system model predictions. They showed that the ion convergence distribution is broadly consistent with Es OR.…”

Section: Introductionmentioning

confidence: 99%

“…Note however, that at higher midlatitudes the DT amplitudes become small compared with SDT ones during most of the year. Owing to its smaller amplitude, the quarterdiurnal tide (QDT) has been analyzed less frequently in the past (Smith et al, 2004), but more recently has attained increasing attention (Liu et al, 2015;Azeem et al, 2016;Jacobi et al, 2017Jacobi et al, , 2018aGuharay et al, 2018;Gong et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Tidal wind shear observed by meteor radar and comparison with sporadic E occurrence rates based on GPS radio occultation observations

Jacobi

Arras

2019

Adv. Radio Sci.

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Abstract. We analyze tidal (diurnal, semidiurnal, terdiurnal, quarterdiurnal) phases and related wind shear in the mesosphere/lower thermosphere as observed by meteor radar over Collm (51.3∘ N, 13.0∘ E). The wind shear phases are compared with those of sporadic E (Es) occurrence rates, which were derived from GPS radio occultation signal-to-noise ratio (SNR) profiles measured by the COSMIC/FORMOSAT-3 satellites. At middle latitudes Es are mainly produced by wind shear, which, in the presence of a horizontal component of the Earth's magnetic field, leads to ion convergence in the region where the wind shear is negative. Consequently, we find good correspondence between radar derived wind shear and Es phases for the semidiurnal, terdiurnal, and quarterdiurnal tidal components. The diurnal tidal wind shear, however, does not correspond to the Es diurnal signal.

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Global distribution of neutral wind shear associated with sporadic E layers derived from GAIA

Cited by 62 publications

References 56 publications

On the Relationship Between E Region Scintillation and ENSO Observed by FORMOSAT‐3/COSMIC

On the Relationship Between E Region Scintillation and ENSO Observed by FORMOSAT‐3/COSMIC

The global climatology of the intensity of ionospheric sporadic <i>E</i> layer

Tidal wind shear observed by meteor radar and comparison with sporadic E occurrence rates based on GPS radio occultation observations

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Global distribution of neutral wind shear associated with sporadic E layers derived from GAIA

Cited by 62 publications

References 56 publications

On the Relationship Between E Region Scintillation and ENSO Observed by FORMOSAT‐3/COSMIC

On the Relationship Between E Region Scintillation and ENSO Observed by FORMOSAT‐3/COSMIC

The global climatology of the intensity of ionospheric sporadic &lt;i&gt;E&lt;/i&gt; layer

Tidal wind shear observed by meteor radar and comparison with sporadic E occurrence rates based on GPS radio occultation observations

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The global climatology of the intensity of ionospheric sporadic <i>E</i> layer