scholarly journals Statistically analyzing the effect of ionospheric irregularity on GNSS radio occultation atmospheric measurement

2021 ◽  
Vol 14 (4) ◽  
pp. 3003-3013
Author(s):  
Mingzhe Li ◽  
Xinan Yue
Keyword(s):  
Radio Occultation ◽  
Data Retrieval ◽  
Satellite System ◽  
Ionospheric Irregularity ◽  
Lower Atmosphere ◽  
Occurrence Rate ◽  
Neutral Atmosphere ◽  
Bending Angle ◽  
F Region ◽  
Global Navigation Satellite

Abstract. The Global Navigation Satellite System (GNSS) atmospheric radio occultation (RO) has been an effective method for exploring Earth's atmosphere. RO signals propagate through the ionosphere before reaching the neutral atmosphere. The GNSS signal is affected by the ionospheric irregularity including the sporadic E (Es) and F region irregularity mainly due to the multipath effect. The effect of ionospheric irregularity on atmospheric RO data has been demonstrated by several studies in terms of analyzing singe cases. However, its statistical effect has not been investigated comprehensively. In this study, based on the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) RO data during 2011–2013, the failed inverted RO events occurrence rate and the bending angle oscillation, which is defined as the standard deviation of the bias between the observed bending angle and the National Center for Atmospheric Research (NCAR) climatology model bending angle between 60 and 80 km, were used for statistical analysis. It is found that at middle and low latitudes during the daytime, the failed inverted RO occurrence and the bending angle oscillation show obvious latitude, longitude, and local time variations, which correspond well with the Es occurrence features. The F region irregularity (FI) contributes to the obvious increase of the failed inverted RO occurrence rate and the bending angle oscillation value during the nighttime over the geomagnetic equatorial regions. For high latitude regions, the Es can increase the failed inverted RO occurrence rate and the bending angle oscillation value during the nighttime. There also exists the seasonal dependency of the failed inverted RO event and the bending angle oscillation. Overall, the ionospheric irregularity effects on GNSS atmospheric RO measurement statistically exist in terms of failed RO event inversion and bending angle oscillation. Awareness of these effects could benefit both the data retrieval and applications of RO in the lower atmosphere.

scholarly journals Statistical analyzing the effect of ionospheric irregularity on GNSS radio occultation atmospheric measurement

2020 ◽  
Author(s):  
Mingzhe Li ◽  
Xinan Yue
Keyword(s):  
Radio Occultation ◽  
Data Retrieval ◽  
Satellite System ◽  
Ionospheric Irregularity ◽  
Lower Atmosphere ◽  
Occurrence Rate ◽  
Neutral Atmosphere ◽  
Bending Angle ◽  
F Region ◽  
Global Navigation Satellite

Abstract. The Global Navigation Satellite System (GNSS) atmospheric radio occultation (RO) has been an effective method for Earth’s atmosphere exploring. RO signals propagate through ionosphere before reaching the neutral atmosphere. The GNSS signal is affected by the ionospheric irregularity including the sporadic E (Es) and the F region irregularity due to mainly multipath effect. The effect of ionospheric irregularity on atmospheric RO data has been demonstrated by several studies in terms of cases. However, its statistical effect has not been investigated comprehensively. In this study, based on the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) RO data during 2011–2013, the failed inverted RO events occurrence rate and the bending angle oscillation, which is defined as the standard deviation of the bias between the observed bending angle and the National Center for Atmospheric Research (NCAR) climatology model bending angle between 60 and 80 km, were used for statistical analysis. It is found that in middle and low latitudes during the daytime, the failed inverted RO occurrence and the bending angle oscillation show obvious latitude, longitude, and local time variations, which correspond well with the Es occurrence features. The F region irregularity (FI) contributes to the obvious increase of the failed inverted RO occurrence rate and the bending angle oscillation value during the nighttime over the geomagnetic equatorial regions. For high latitude regions, the Es can increase the failed inverted RO occurrence rate and the bending angle oscillation value during the nighttime. There also exists the seasonal dependency of the failed inverted RO event and the bending angle oscillation. Overall, the ionospheric irregularity effects on GNSS atmospheric RO measurement exist in terms of failed RO event inversion and bending angle oscillation statistically. Awareness of these effects could benefit both the data retrieval and applications of RO in the lower atmosphere.

scholarly journals The FengYun-3C radio occultation sounder GNOS: a review of the mission and its early results and science applications

2018 ◽  
Vol 11 (10) ◽  
pp. 5797-5811 ◽  
Author(s):  
Yueqiang Sun ◽  
Weihua Bai ◽  
Congliang Liu ◽  
Yan Liu ◽  
Qifei Du ◽  
...  
Keyword(s):  
Quality Evaluation ◽  
Radio Occultation ◽  
Global Climate ◽  
Weather Prediction ◽  
Satellite System ◽  
Navigation Satellite ◽  
Neutral Atmosphere ◽  
Scientific Applications ◽  
Early Results ◽  
Global Navigation Satellite

Abstract. The Global Navigation Satellite System (GNSS) Occultation Sounder (GNOS) is one of the new-generation payloads on board the Chinese FengYun 3 (FY-3) series of operational meteorological satellites for sounding the Earth's neutral atmosphere and ionosphere. FY-3C GNOS, on board the FY-3 series C satellite launched in September 2013, was designed to acquire setting and rising radio occultation (RO) data by using GNSS signals from both the Chinese BeiDou Navigation Satellite System (BDS) and the US Global Positioning System (GPS). So far, the GNOS measurements and atmospheric and ionospheric data products have been validated and evaluated and then been used for atmosphere- and ionosphere-related scientific applications. This paper reviews the FY-3C GNOS instrument, RO data processing, data quality evaluation, and preliminary research applications according to the state-of-the-art status of the FY-3C GNOS mission and related publications. The reviewed data validation and application results demonstrate that the FY-3C GNOS mission can provide accurate and precise atmospheric and ionospheric GNSS (i.e., GPS and BDS) RO profiles for numerical weather prediction (NWP), global climate monitoring (GCM), and space weather research (SWR). The performance of the FY-3C GNOS product quality evaluation and scientific applications establishes confidence that the GNOS data from the series of FY-3 satellites will provide important contributions to NWP, GCM, and SWR scientific communities.

scholarly journals The FengYun-3C radio occultation sounder GNOS: a review of the mission and its early results and science applications

2018 ◽  
Author(s):  
Yueqiang Sun ◽  
Weihua Bai ◽  
Congliang Liu ◽  
Yan Liu ◽  
Qifei Du ◽  
...  
Keyword(s):  
Quality Evaluation ◽  
Radio Occultation ◽  
Global Climate ◽  
Weather Prediction ◽  
Satellite System ◽  
Neutral Atmosphere ◽  
Scientific Applications ◽  
Early Results ◽  
Beidou System ◽  
Global Navigation Satellite

Abstract. The Global Navigation Satellite System (GNSS) occultation sounder (GNOS) is one of the new generation payloads onboard the Chinese FengYun 3 (FY-3) series of operational meteorological satellites for sounding the Earth’s neutral atmosphere and ionosphere. FY-3C GNOS, onboard the FY-3 satellite C launched in September 2013, was designed for acquiring setting and rising radio occultation (RO) data by using GNSS signals from both the Chinese BeiDou System (BDS) and the U.S. Global Positioning System (GPS). So far, the GNOS measurements and atmospheric and ionospheric data products have been validated and evaluated and then been used for atmosphere and ionosphere related scientific applications. This paper reviews the FY-3C GNOS instrument, RO data processing, data quality evaluation, and research applications. The reviewed data validation and application results demonstrate that the FY-3C GNOS mission can provide accurate and precise atmospheric and ionospheric GNSS (i.e., GPS and BDS) RO profiles for numerical weather prediction (NWP), global climate monitoring (GCM) and space weather research (SWR). The performance of the FY-3C GNOS product quality evaluation and scientific applications establishes confidence that the GNOS data from the series of FY-3 satellites will provide important contributions to SWP, GCM and SWR scientific communities.

scholarly journals Tropical cyclones vertical structure from GNSS radio occultation: an archive covering the period 2001–2018

2020 ◽  
Author(s):  
Elżbieta Lasota ◽  
Andrea K. Steiner ◽  
Gottfried Kirchengast ◽  
Riccardo Biondi
Keyword(s):  
Tropical Cyclones ◽  
Vertical Structure ◽  
Radio Occultation ◽  
Weather Conditions ◽  
Satellite System ◽  
Spatial Distance ◽  
Correct Prediction ◽  
Data Files ◽  
High Vertical Resolution ◽  
Global Navigation Satellite

Abstract. Tropical Cyclones (TC) are natural destructive phenomena, which affect wide tropical and subtropical areas every year. Although the correct prediction of their tracks and intensity has improved over recent years, the knowledge about their structure and development is still insufficient. The Global Navigation Satellite System (GNSS) Radio Occultation (RO) technique can provide a better understanding of the TC because it enables to probe the atmospheric vertical structure with high accuracy, high vertical resolution, and global coverage in any weather conditions. In this work, we create an archive of co-located TC best tracks and RO profiles covering the period 2001–2018 and providing a complete view of the storms since the pre-cyclone status to the cyclone disappearance. We collected 1822 TC best tracks from the International Best Track Archive for Climate Stewardship and co-located them with 48313 RO profiles from seven satellite missions processed by Wegener Center for Climate and Global Change. We provide information about location and intensity of the TC, RO vertical profiles co-located within 3 hours and 500 km from the TC eye centre, and exact information about temporal and spatial distance between the TC centre and the RO mean tangent point. A statistical analysis shows how the archive well covers all the ocean basins and all the intensity categories. We finally demonstrate the application of this dataset to investigate the vertical structure for one TC example case. All the data files, separately for each TC, are publicly available in NetCDF format at https://doi.org/10.25364/WEGC/TC-RO1.0:2020.1 (Lasota et al., 2020).

scholarly journals Analysis of ionospheric structure influences on residual ionospheric errors in GNSS radio occultation bending angles based on ray tracing simulations

2018 ◽  
Vol 11 (4) ◽  
pp. 2427-2440 ◽  
Author(s):  
Congliang Liu ◽  
Gottfried Kirchengast ◽  
Yueqiang Sun ◽  
Kefei Zhang ◽  
Robert Norman ◽  
...  
Keyword(s):  
Impact Parameter ◽  
Radio Occultation ◽  
Global Climate ◽  
Weather Prediction ◽  
Signal Propagation ◽  
Satellite System ◽  
Primary Role ◽  
Dual Frequency ◽  
Bending Angle ◽  
Bending Angles

Abstract. The Global Navigation Satellite System (GNSS) radio occultation (RO) technique is widely used to observe the atmosphere for applications such as numerical weather prediction and global climate monitoring. The ionosphere is a major error source to RO at upper stratospheric altitudes, and a linear dual-frequency bending angle correction is commonly used to remove the first-order ionospheric effect. However, the higher-order residual ionospheric error (RIE) can still be significant, so it needs to be further mitigated for high-accuracy applications, especially from 35 km altitude upward, where the RIE is most relevant compared to the decreasing magnitude of the atmospheric bending angle. In a previous study we quantified RIEs using an ensemble of about 700 quasi-realistic end-to-end simulated RO events, finding typical RIEs at the 0.1 to 0.5 µrad noise level, but were left with 26 exceptional events with anomalous RIEs at the 1 to 10 µrad level that remained unexplained. In this study, we focused on investigating the causes of the high RIE of these exceptional events, employing detailed along-ray-path analyses of atmospheric and ionospheric refractivities, impact parameter changes, and bending angles and RIEs under asymmetric and symmetric ionospheric structures. We found that the main causes of the high RIEs are a combination of physics-based effects – where asymmetric ionospheric conditions play the primary role, more than the ionization level driven by solar activity – and technical ray tracer effects due to occasions of imperfect smoothness in ionospheric refractivity model derivatives. We also found that along-ray impact parameter variations of more than 10 to 20 m are possible due to ionospheric asymmetries and, depending on prevailing horizontal refractivity gradients, are positive or negative relative to the initial impact parameter at the GNSS transmitter. Furthermore, mesospheric RIEs are found generally higher than upper-stratospheric ones, likely due to being closer in tangent point heights to the ionospheric E layer peaking near 105 km, which increases RIE vulnerability. In the future we will further improve the along-ray modeling system to fully isolate technical from physics-based effects and to use it beyond this work for additional GNSS RO signal propagation studies.

scholarly journals Assimilation of GNSS radio occultation observations in GRAPES

2014 ◽  
Vol 7 (11) ◽  
pp. 3935-3946 ◽  
Author(s):  
Y. Liu ◽  
J. Xue
Keyword(s):  
Radio Occultation ◽  
Satellite System ◽  
Observation Error ◽  
Data Quality Control ◽  
Forecast System ◽  
China Meteorological Administration ◽  
Environmental Prediction ◽  
Global Navigation Satellite ◽  
Impact Experiments ◽  
Positive Effect

Abstract. This paper reviews the development of the global navigation satellite system (GNSS) radio occultation (RO) observations assimilation in the Global/Regional Assimilation and PrEdiction System (GRAPES) of China Meteorological Administration, including the choice of data to assimilate, the data quality control, the observation operator, the tuning of observation error, and the results of the observation impact experiments. The results indicate that RO data have a significantly positive effect on analysis and forecast at all ranges in GRAPES, not only in the Southern Hemisphere where conventional observations are lacking but also in the Northern Hemisphere where data are rich. It is noted that a relatively simple assimilation and forecast system in which only the conventional and RO observation are assimilated still has analysis and forecast skill even after nine months integration, and the analysis difference between both hemispheres is gradually reduced with height when compared with NCEP (National Centers for Environmental Prediction) analyses. Finally, as a result of the new on-board payload of the Chinese FengYun-3 (FY-3) satellites, the research status of the RO of FY-3 satellites is also presented.

scholarly journals An introduction to FY3 GNOS instrument and its performace tested on ground

2014 ◽  
Vol 7 (1) ◽  
pp. 703-726
Author(s):  
W. Bai ◽  
Y. Sun ◽  
Q. Du ◽  
G. Yang ◽  
Z. Yang ◽  
...  
Keyword(s):  
Weather Prediction ◽  
Measurement Data ◽  
Atmospheric Temperature ◽  
Satellite System ◽  
Navigation Satellite ◽  
Neutral Atmosphere ◽  
Satellite Systems ◽  
Lower Elevation ◽  
Electron Density Profiles ◽  
Global Navigation Satellite

Abstract. The FY3 GNOS (GNSS Occultation Sounder) mission is a GNSS (Global Navigation Satellite System) radio occultation mission of China for remote sensing of Earth's neutral atmosphere and the ionosphere. GNOS will use both the Global Positioning System (GPS) and the Beidou navigation satellite systems on the China Feng-Yun-3 (FY3) series satellites. The first FY3-C was launched at 03:03 UTC, 23 September 2013. GNOS was developed by Center for Space Science and Applied Research, Chinese Academy of Sciences (CSSAR). It will provide vertical profiles of atmospheric temperature, pressure, and humidity, as well as ionospheric electron density profiles on a global basis. These data will be used for numerical weather prediction, climate research, and ionospheric research and space weather. This paper describes the FY3 GNOS mission and the GNOS instrument characteristics. It presents simulation results of the number and distribution of GNOS occultation events with the Regional Beidou constellation and the full GPS constellation, under the limitation of the GNOS instrument occultation channel number. This paper presents the instrument performance as derived from analysis of measurement data in laboratory and mountain-based occultation validation experiments at Mt. Wuling in Hebei Province. The mountain-based GNSS occultation validation tests show that GNOS can acquire or track lower elevation radio signal for rising or setting occultation events. The refractivity profiles of GNOS obtained during the mountain-based experiment were compared with those from radiosondes. The results show that the refractivity profiles obtained by GNOS are consistent with those from the radiosonde. The RMS of the differences between the GNOS and radiosonde refractivities is less than 3%.

scholarly journals Preliminary validation of refractivity from a new radio occultation sounder GNOS/FY-3C

2015 ◽  
Vol 8 (9) ◽  
pp. 9009-9044 ◽  
Author(s):  
M. Liao ◽  
P. Zhang ◽  
G. L. Yang ◽  
Y. M. Bi ◽  
Y. Liu ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Radio Occultation ◽  
Weather Prediction ◽  
Satellite System ◽  
Navigation Satellite ◽  
Near Surface ◽  
Vertical Range ◽  
New Radio ◽  
Atmospheric Sounding ◽  
Global Navigation Satellite

Abstract. As a new member of space-based radio occultation sounder, the GNOS (Global Navigation Satellite System Occultation Sounder) mounted on FY-3C has been carrying out the atmospheric sounding since 23 September 2013. GNOS takes a daily measurement up to 800 times with GPS (Global Position System) and Chinese BDS (BeiDou navigation satellite) signals. The refractivity profiles from GNOS are compared with the co-located ECMWF (European Centre for Medium-Range Weather Forecasts) analyses in this paper. Bias and standard deviation have being calculated as the function of altitude. The mean bias is about 0.2 % from the near surface to 35 km. The average standard deviation is within 2 % while it is down to about 1 % in the range 5–30 km where best soundings are usually made. To evaluate the performance of GNOS, COSMIC (Constellation Observing System for Meteorology, Ionosphere and Climate) and GRAS/METOP-A (GNSS Receiver for Atmospheric Sounding) data are also compared to ECMWF analyses as the reference. The results show that GNOS/FY-3C meets the requirements of the design well. It possesses a sounding capability similar to COSMIC and GRAS in the vertical range of 0–30 km, though it needs improvement in higher altitude. Generally, it provides a new data source for global NWP (numerical weather prediction) community.

scholarly journals Application of the Fengyun 3 C GNSS occultation sounder for assessing the global ionospheric response to a magnetic storm event

2019 ◽  
Vol 12 (3) ◽  
pp. 1483-1493 ◽  
Author(s):  
Weihua Bai ◽  
Guojun Wang ◽  
Yueqiang Sun ◽  
Jiankui Shi ◽  
Guanglin Yang ◽  
...  
Keyword(s):  
Magnetic Storm ◽  
Radio Occultation ◽  
Correlation Coefficients ◽  
Satellite System ◽  
Storm Event ◽  
Calibration Data ◽  
Long Term Stability ◽  
Negative Effect ◽  
Occultation Data ◽  
Global Navigation Satellite

Abstract. The rapid advancement of global navigation satellite system (GNSS) occultation technology in recent years has made it one of the most advanced space-based remote sensing technologies of the 21st century. GNSS radio occultation has many advantages, including all-weather operation, global coverage, high vertical resolution, high precision, long-term stability, and self-calibration. Data products from GNSS occultation sounding can greatly enhance ionospheric observations and contribute to space weather monitoring, forecasting, modeling, and research. In this study, GNSS occultation sounder (GNOS) results from a radio occultation sounding payload aboard the Fengyun 3 C (FY3-C) satellite were compared with ground-based ionosonde observations. Correlation coefficients for peak electron density (NmF2) derived from GNOS Global Position System (GPS) and Beidou navigation system (BDS) products with ionosonde data were higher than 0.9, and standard deviations were less than 20 %. Global ionospheric effects of the strong magnetic storm event in March 2015 were analyzed using GNOS results supported by ionosonde observations. The magnetic storm caused a significant disturbance in NmF2 level. Suppressed daytime and nighttime NmF2 levels indicated mainly negative storm conditions. In two longitude section zones of geomagnetic inclination between 40 and 80∘, the results of average NmF2 observed by GNOS and ground-based ionosondes showed the same basic trends during the geomagnetic storm and confirmed the negative effect of this storm event on the ionosphere. The analysis demonstrates the reliability of the GNSS radio occultation sounding instrument GNOS aboard the FY3-C satellite and confirms the utility of ionosphere products from GNOS for statistical and event-specific ionospheric physical analyses. Future FY3 series satellites and increasing numbers of Beidou navigation satellites will provide increasing GNOS occultation data on the ionosphere, which will contribute to ionosphere research and forecasting applications.

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