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 Assimilation of GNSS radio occultation observations in GRAPES

2014 ◽  
Vol 7 (7) ◽  
pp. 7613-7639
Author(s):  
Y. Liu ◽  
J. Xue
Keyword(s):  
Radio Occultation ◽  
Satellite System ◽  
Observation Error ◽  
Prediction System ◽  
Data Quality Control ◽  
Forecast System ◽  
China Meteorological Administration ◽  
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 Enviromental Prediction) analysis. Finally, as a result of the new onboard 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 Analysis Study of FORMOSAT-7/COSMIC-2 Radio Occultation Data in the Troposphere

2021 ◽  
Vol 13 (4) ◽  
pp. 717
Author(s):  
Shu-Ya Chen ◽  
Chian-Yi Liu ◽  
Ching-Yuang Huang ◽  
Shen-Cha Hsu ◽  
Hsiu-Wen Li ◽  
...  
Keyword(s):  
Radio Occultation ◽  
Water Vapor Pressure ◽  
Processing System ◽  
Lower Troposphere ◽  
Ground Truth ◽  
Satellite System ◽  
Spatial Distance ◽  
Mean Differences ◽  
Environmental Prediction ◽  
Global Navigation Satellite

This study investigates the Global Navigation Satellite System (GNSS) radio occultation (RO) data from FORMOSAT-7/COSMIC-2 (FS7/C2), which provides considerably more and deeper profiles at lower latitudes than those from the former FORMOSAT-3/COSMIC (FS3/C). The statistical analysis of six-month RO data shows that the rate of penetration depth below 1 km height within ±45° latitudes can reach 80% for FS7/C2, significantly higher than 40% for FS3/C. For verification, FS7/C2 RO data are compared with the observations from chartered missions that provided aircraft dropsondes and on-board radiosondes, with closer observation times and distances from the oceanic RO occultation over the South China Sea and near a typhoon circulation region. The collocated comparisons indicate that FS7/C2 RO data are reliable, with small deviations from the ground-truth observations. The RO profiles are compared with collocated radiosondes, RO data from other missions, global analyses of ERA5 and National Centers for Environmental Prediction (NCEP) final (FNL), and satellite retrievals of NOAA Unique Combined Atmospheric Processing System (NCAPS). The comparisons exhibit consistent vertical variations, showing absolute mean differences and standard deviations of temperature profiles less than 0.5 °C and 1.5 °C, respectively, and deviations of water vapor pressure within 2 hPa in the lower troposphere. From the latitudinal distributions of mean difference and standard deviation (STD), the intertropical convergence zone (ITCZ) is evidentially shown in the comparisons, especially for the NUCAPS, which shows a larger deviation in moisture when compared to FS7/C2 RO data. The sensitivity of data collocation in time departure and spatial distance among different datasets are presented in this study as well.

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 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.

Improvement in the Use of an Operational Constellation of GPS Radio Occultation Receivers in Weather Forecasting

2010 ◽  
Vol 25 (2) ◽  
pp. 749-767 ◽  
Author(s):  
L. Cucurull
Keyword(s):  
Radio Occultation ◽  
Weather Forecasting ◽  
Model Performance ◽  
Observation Error ◽  
Gps Radio Occultation ◽  
Additional Information ◽  
Model Skill ◽  
Global Data Assimilation System ◽  
Control Procedures ◽  
Environmental Prediction

Abstract As of May 2007, the National Centers for Environmental Prediction (NCEP) implemented a new Global Data Assimilation System. This system incorporated the assimilation of global positioning system (GPS) radio occultation (RO) profiles from the Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) mission, which was launched in April 2006. Since then, this new type of observation has been shown to provide additional information on the thermodynamic state of the atmosphere, resulting in a significant increase in the model skill. Recent updates of the analysis and modeling codes have required a revision of the algorithm that assimilates GPS RO data. In addition, some modifications in the processing of the observations have further enhanced the need for a revisiting of the assimilation code. Better characterizations of the quality control procedures, observation error structure, and forward modeling for the GPS RO observations are described. The updated system significantly improves the data usage, in particular in the tropics. Different sets of the atmospheric refractive indices are also evaluated in this study. The model performance is proven to be quite sensitive to the chosen coefficients and a reevaluation of these constants is recommended within the GPS community. The new assimilation configuration results in an improvement in the anomaly correlation scores for the Southern Hemisphere extratropics (∼4.5 h for the 500-mb geopotential heights at day 7) and a reduction of the high- and low-level tropical wind errors. Overall, the benefits of using COSMIC on top of all the other observations used in the operational system are still very significant. The loss in model skill when COSMIC is removed from the observing system is remarkable at day 4 (∼8 h) and steadily increases beyond 12 h with the extended forecast range.

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.

scholarly journals Application of GPS radio occultation to the assessment of temperature profile retrievals from microwave and infrared sounders

2014 ◽  
Vol 7 (11) ◽  
pp. 3751-3762 ◽  
Author(s):  
M. Feltz ◽  
R. Knuteson ◽  
S. Ackerman ◽  
H. Revercomb
Keyword(s):  
Temperature Profile ◽  
Radio Occultation ◽  
Satellite System ◽  
Advanced Technology ◽  
Similar Time ◽  
Gps Radio Occultation ◽  
Common Reference ◽  
Spatial Coverage ◽  
Atmospheric Sounding ◽  
Global Navigation Satellite

Abstract. Comparisons of satellite temperature profile products from GPS radio occultation (RO) and hyperspectral infrared (IR)/microwave (MW) sounders are made using a previously developed matchup technique. The profile matchup technique matches GPS RO and IR/MW sounder profiles temporally, within 1 h, and spatially, taking into account the unique RO profile geometry and theoretical spatial resolution by calculating a ray-path averaged sounder profile. The comparisons use the GPS RO dry temperature product. Sounder minus GPS RO differences are computed and used to calculate bias and rms profile statistics, which are created for global and 30° latitude zones for selected time periods. These statistics are created from various combinations of temperature profile data from the Constellation Observing System for Meteorology, Ionosphere & Climate (COSMIC) network, Global Navigation Satellite System Receiver for Atmospheric Sounding (GRAS) instrument, and the Atmospheric Infrared Sounder (AIRS)/Advanced Microwave Sounding Unit (AMSU), Infrared Atmospheric Sounding Interferometer (IASI)/AMSU, and Crosstrack Infrared Sounder (CrIS)/Advanced Technology Microwave Sounder (ATMS) sounding systems. By overlaying combinations of these matchup statistics for similar time and space domains, comparisons of different sounders' products, sounder product versions, and GPS RO products can be made. The COSMIC GPS RO network has the spatial coverage, time continuity, and stability to provide a common reference for comparison of the sounder profile products. The results of this study demonstrate that GPS RO has potential to act as a common temperature reference and can help facilitate inter-comparison of sounding retrieval methods and also highlight differences among sensor product versions.

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