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

Abstract

There have been a number of papers reporting that the statistical occurrence rate of the sporadic E (Es) layer depends not only on the local time and season but also on the geographical location, implying that geographical and seasonal dependence in vertical neutral wind shear is one of the factors responsible for the geographical and seasonal dependence in Es layer occurrences rate. To study the role of neutral wind shear in the global distribution of the Es layer occurrence rate, we employ a self‐consistent atmosphere‐ionosphere coupled model called GAIA (Ground‐to‐topside model of Atmosphere and Ionosphere for Aeronomy), which incorporates meteorological reanalysis data in the lower atmosphere. The average distribution of neutral wind shear in the lower thermosphere is derived for the June–August and December–February periods, and the global distribution of vertical ion convergence is obtained to estimate the Es layer occurrence rate. It is found that the local and seasonal dependence of neutral wind shear is an important factor in determining the dependence of the Es layer occurrence rate on geographical distribution and seasonal variation. However, there are uncertainties in the simulated vertical neutral wind shears, which have larger scales than the observed wind shear scales. Furthermore, other processes such as localization of magnetic field distribution, background metallic ion distribution, ionospheric electric fields, and chemical processes of metallic ions are also likely to make an important contribution to geographical distribution and seasonal variation of the Es occurrence rate.

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

“…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.…”

“…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, ).…”

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

“…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.…”

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

“…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.…”

“…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).…”