scholarly journals Comparison of the Tidal Signatures in Sporadic E and Vertical Ion Convergence Rate, Using FORMASAT-3/COSMIC Radio Occultation Observations and GAIA Model

2021 ◽  
Author(s):  
Sahar Sobhkhiz-Miandehi ◽  
Yosuke Yamazaki ◽  
Christina Arras ◽  
Yasunobu Miyoshi ◽  
Hiroyuki Shinagawa
Keyword(s):  
Radio Occultation ◽  
Thin Layers ◽  
Atmospheric Tides ◽  
Occurrence Rate ◽  
Cosmic Radio ◽  
Lunar Tides ◽  
E Region ◽  
Global Coverage ◽  
Sporadic E ◽  
Occultation Data

Abstract Sporadic E or Es is a transient phenomenon where thin layers of enhanced electron density appear in the ionospheric E region (90-120 km altitude). The neutral wind shear caused by atmospheric tides can lead ions to converge vertically at E-region heights and form the Es layers. This research aims to determine the role of atmospheric solar and lunar tides in Es occurrence. For this purpose, radio occultation data of FORMASAT-3/COSMIC have been used, which provides complete global coverage of Es events. Moreover, GAIA model simulations have been employed to evaluate the vertical ion convergence induced by solar tides. The results show both migrating and non-migrating solar tidal signatures and the semidiurnal migrating lunar tidal signature in Es occurrence. The seasonal variation of the migrating solar tidal components of Es is in good agreement with those in the vertical ion convergence derived from GAIA. Furthermore, some non-migrating components of solar tides, including semidiurnal westward wavenumbers 1 and 3 and diurnal eastward wavenumbers 2 and 3, also significantly affect the Es occurrence rate.

Tidal Signature Detection in Midlatitude Sporadic E Occurrence Rate, Using FORMOSAT-3/COSMIC Radio Occultation Data

2021 ◽  
Author(s):  
Sahar Sobhkhiz ◽  
Yosuke Yamazaki ◽  
Christina Arras
Keyword(s):  
Radio Occultation ◽  
Thin Layers ◽  
Occurrence Rate ◽  
Horizontal Wind ◽  
Cosmic Radio ◽  
Radio Communications ◽  
E Region ◽  
Sporadic E ◽  
Occultation Data ◽  
Radio Occultation Data

<p>Sporadic E (Es) is a transient phenomenon where thin layers of enhanced electron density appear in the ionospheric E region (90-120 km altitude). Es can influence radio propagation, and its global characteristics have been of great interest to radio communications and navigations. Atmospheric diurnal and semidiurnal tides cause horizontal wind shears at E-region heights by giving rise to ions and electrons' vertical motions. These shears will lead to the formation of Es layers. This research aims to study the role of atmospheric solar and lunar tides in Mid-latitude Es occurrence. For this purpose, radio occultation data from FORMASAT-3/COSMIC mission of 11 years (2007 to 2017), which provide complete global coverage, have been used. The results show both lunar and solar tidal signatures in Es occurrence. These tidal signatures are longitudinally dependent, which can result from non-migrating tides or modulation of migrating tidal signatures by zonally varying geomagnetic field.</p>

Analyzing the Diurnal Cycle by Bayesian Interpolation on a Sphere for Mapping GNSS Radio Occultation Data

2021 ◽  
Vol 38 (5) ◽  
pp. 951-961
Author(s):  
Stephen S. Leroy ◽  
Chi O. Ao ◽  
Olga P. Verkhoglyadova ◽  
Mayra I. Oyola
Keyword(s):  
Diurnal Cycle ◽  
Radio Occultation ◽  
Basis Functions ◽  
Atmospheric Tides ◽  
Spherical Harmonic Degree ◽  
Construct Maps ◽  
Bayesian Interpolation ◽  
Occultation Data ◽  
High Degree ◽  
Radio Occultation Data

AbstractBayesian interpolation has previously been proposed as a strategy to construct maps of radio occultation (RO) data, but that proposition did not consider the diurnal dimension of RO data. In this work, the basis functions of Bayesian interpolation are extended into the domain of the diurnal cycle, thus enabling monthly mapping of radio occultation data in synoptic time and analysis of the atmospheric tides. The basis functions are spherical harmonics multiplied by sinusoids in the diurnal cycle up to arbitrary spherical harmonic degree and diurnal cycle harmonic. Bayesian interpolation requires a regularizer to impose smoothness on the fits it produces, thereby preventing the overfitting of data. In this work, a formulation for the regularizer is proposed and the most probable values of the parameters of the regularizer determined. Special care is required when obvious gaps in the sampling of the diurnal cycle are known to occur in order to prevent the false detection of statistically significant high-degree harmonics of the diurnal cycle in the atmosphere. Finally, this work probes the ability of Bayesian interpolation to generate a valid uncertainty analysis of the fit. The postfit residuals of Bayesian interpolation are dominated not by measurement noise but by unresolved variability in the atmosphere, which is statistically nonuniform across the globe, thus violating the central assumption of Bayesian interpolation. The problem is ameliorated by constructing maps of RO data using Bayesian interpolation that partially resolve the temporal variability of the atmosphere, constructing maps for approximately every 3 days of RO data.

Impact of FORMOSAT-3/COSMIC radio occultation data on the prediction of super cyclone Gonu (2007): a case study

2013 ◽  
Vol 70 (2) ◽  
pp. 1209-1230 ◽  
Author(s):  
S. K. A. V. Prasad Rao Anisetty ◽  
Ching-Yuang Huang ◽  
Shu-Ya Chen
Keyword(s):  
Radio Occultation ◽  
Cosmic Radio ◽  
Super Cyclone ◽  
Occultation Data ◽  
Radio Occultation Data
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