Morphology of sporadic <i>E</i> layer retrieved from COSMIC GPS radio occultation measurements: Wind shear theory examination

Chu, Yen Hsyang; Wang, C. Y.; Wu, Kuo Hui; Chen, K. T.; Tzeng, K. J.; Su, Ching Lun; Feng, Wuhu; Plane, J. M. C.

doi:10.1002/2013ja019437

Cited by 123 publications

(294 citation statements)

References 61 publications

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“…Specifically, they provided direct proof of the control exerted by the Earth's geomagnetic field on E s for the first time, and this supported the wind shear theory strongly (Haldoupis, 2011). These statistics are further confirmed by Chu et al (2014) and Yeh et al (2012), based on a large amount of COSMIC data. Through both simulation and real-data analysis, Zeng and Sokolovskiy (2010) revealed that the E s cloud aligned with the wave propagation direction could cause defocusing of the GPS RO signal, accompanied by scintillation above and below the defocusing region due to the interference of direct and refracted radio waves.…”

Section: Introductionsupporting

confidence: 60%

“…The E s is controlled by the tidal wind and therefore also shows tidal structures in its formation and descent. Main tidal components can be diurnal, semidiurnal, and even terdiurnal and quarterdiurnal (Arras et al, 2009;Chu et al, 2014;Fytterer et al, 2013;Wu et al, 2005). All these factors make the complex E s layer structures understandable.…”

Section: Multiple E S Layers In One Profilementioning

confidence: 99%

“…The identification of E s occurrence is different from paper to paper (Arras et al, 2008;Chu et al, 2014;Dou et al, 2010;Hocke et al, 2001;Wu et al, 2005;Yeh et al, 2012;Zeng and Sokolovskiy, 2010). Hocke et al (2001) and Dou et al (2010) derived E s occurrence from the fluctuations of RO inverted electron density profiles.…”

Section: Introductionmentioning

confidence: 98%

“…Recently, the GNSS (global navigation satellite system)-based radio occultation (RO) technique has shown great capability in detecting the global E s occurrence by using high-resolution signal-to-noise ratio (SNR) data (Arras et al, 2008;Chu et al, 2014;Hocke et al, 2001;Wu et al, 2005;Yeh et al, 2012;Zeng and Sokolovskiy, 2010). GNSS RO technique has proven to be a powerful tool in monitoring climate, weather, and space weather (Anthes, 2011;Foelsche et al, 2011;Liu et al, 2010;Schreiner et al, 2007;Zhang et al, 2011;Yue et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

“…Wu et al (2005) and Arras et al (2008) calculated the standard deviation of filtered and normalized SNR and identified E s occurrence through either the maximum standard deviation or a threshold. Chu et al (2014) applied a stricter criterion on both the amplitude and phase fluctuations of L1 and L2 signals to avoid potential influences from the instrument and measurement noise. In this study, the 50 Hz amplitude and phase observations made by the COSMIC occultation antennas and archived at the University Corporation for Atmospheric Research (UCAR) COSMIC Data Analysis and Archive Center (CDAAC) level1b atmPhs files will be used.…”

Section: Introductionmentioning

confidence: 99%

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Case study on complex sporadic E layers observed by GPS radio occultations

et al. 2015

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Abstract. The occurrence of sporadic E (E s ) layers has been a hot scientific topic for a long time. The GNSS (global navigation satellite system)-based radio occultation (RO) has proven to be a powerful technique for detecting the global E s layers. In this paper, we focus on some cases of complex E s layers based on the RO data from multiple missions processed in UCAR/CDAAC (University Corporation for Atmospheric Research (UCAR) the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) Data Analysis and Archive Center (CDAAC)). We first show some examples of multiple E s layers occurred in one RO event. Based on the evaluations between colocated simultaneous RO events and between RO and lidar observations, it could be concluded that some of these do manifest the multiple E s layer structures. We then show a case of the occurrence of E s in a broad region during a certain time interval. The result is then validated by independent ionosondes observations. It is possible to explain these complex E s structures using the popular wind shear theory. We could map the global E s occurrence routinely in the near future, given that more RO data will be available. Further statistical studies will enhance our understanding of the E s mechanism. The understanding of E s should benefit both E s -based long-distance communication and accurate neutral RO retrievals.

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Section: Introductionsupporting

confidence: 60%

Section: Multiple E S Layers In One Profilementioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Case study on complex sporadic E layers observed by GPS radio occultations

et al. 2015

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Improvement of GPS radio occultation retrieval error of E region electron density: COSMIC measurement and IRI model simulation

Chu

2015

JGR Space Physics

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In this article, we use the International Reference Ionosphere (IRI) model to simulate temporal and spatial distributions of global E region electron densities retrieved by the FORMOSAT-3/COSMIC satellites by means of GPS radio occultation (RO) technique. Despite regional discrepancies in the magnitudes of the E region electron density, the IRI model simulations can, on the whole, describe the COSMIC measurements in quality and quantity. On the basis of global ionosonde network and the IRI model, the retrieval errors of the global COSMIC-measured E region peak electron density (N m E) from July 2006 to July 2011 are examined and simulated. The COSMIC measurement and the IRI model simulation both reveal that the magnitudes of the percentage error (PE) and root mean-square-error (RMSE) of the relative RO retrieval errors of the N m E values are dependent on local time (LT) and geomagnetic latitude, with minimum in the early morning and at high latitudes and maximum in the afternoon and at middle latitudes. In addition, the seasonal variation of PE and RMSE values seems to be latitude dependent. After removing the IRI model-simulated GPS RO retrieval errors from the original COSMIC measurements, the average values of the annual and monthly mean percentage errors of the RO retrieval errors of the COSMIC-measured E region electron density are, respectively, substantially reduced by a factor of about 2.95 and 3.35, and the corresponding root-mean-square errors show averaged decreases of 15.6% and 15.4%, respectively. It is found that, with this process, the largest reduction in the PE and RMSE of the COSMIC-measured N m E occurs at the equatorial anomaly latitudes 10°N-30°N in the afternoon from 14 to 18 LT, with a factor of 25 and 2, respectively. Statistics show that the residual errors that remained in the corrected COSMIC-measured N m E vary in a range of À20% to 38%, which are comparable to or larger than the percentage errors of the IRI-predicted N m E fluctuating in a range of À6.5% to 20%.

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Effect of small‐scale ionospheric variability on GNSS radio occultation data quality

Verkhoglyadova

Mannucci

et al. 2015

JGR Space Physics

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Global Navigation Satellite Systems (GNSS) radio occultation (RO) measurements are sensitive to thin ionization layers and small‐scale ionosphere structures. To evaluate error bounds and possible biases in atmospheric retrievals, we characterized ionospheric irregularities encountered in the affected profiles by analyzing the L1 signal‐to‐noise ratio (SNR) variability at E layer altitudes (from 90 km to 130 km). New metrics to analyze statistical effects of small‐scale ionospheric irregularities on refractivity retrievals are proposed. We analyzed refractivity (N) retrievals with Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) ROs in 2011. Using refractivity from European Centre for Medium‐Range Weather Forecasts (ECMWF) analysis (NECMWF) as the reference data set, we studied statistical properties of the fractional refractivity bias (ΔN) defined by the difference (NECMWF − N)/NECMWF and averaged in the altitude range from 20 to 25 km for each individual profile. We found that (1) persistently larger variability of the L1 SNR as measured by the interquartile range (IQR) existed when the occultation tangent point was in the 90 km to 110 km altitude range than at higher E layer altitudes; (2) the upper limits on the fractional refractivity bias for COSMIC ROs are 0.06% (for daytime local time), 0.1% (for nighttime local time), and ~0.01% (for all local times); (3) distributions of ΔN are non‐Gaussian (leptokurtic); (4) latitudinal distributions of small and large ΔN for different levels of ionospheric variability show large tails (NECMWF > N) occurring around the Himalaya and the Andes regions, which are possibly due to biases in ECMWF analysis. We conclude that the refractivity bias due to small‐scale irregularities is small below 25 km altitude and can be neglected.

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Morphology of sporadic E layer retrieved from COSMIC GPS radio occultation measurements: Wind shear theory examination

Cited by 123 publications

References 61 publications

Case study on complex sporadic E layers observed by GPS radio occultations

Case study on complex sporadic E layers observed by GPS radio occultations

Improvement of GPS radio occultation retrieval error of E region electron density: COSMIC measurement and IRI model simulation

Effect of small‐scale ionospheric variability on GNSS radio occultation data quality

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