{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,9]],"date-time":"2026-04-09T12:09:20Z","timestamp":1775736560689,"version":"3.50.1"},"reference-count":87,"publisher":"MDPI AG","issue":"21","license":[{"start":{"date-parts":[[2022,11,7]],"date-time":"2022-11-07T00:00:00Z","timestamp":1667779200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100000192","name":"National Oceanic and Atmospheric Administration","doi-asserted-by":"publisher","award":["1305M221FNEEO0212"],"award-info":[{"award-number":["1305M221FNEEO0212"]}],"id":[{"id":"10.13039\/100000192","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100000192","name":"National Oceanic and Atmospheric Administration","doi-asserted-by":"publisher","award":["2054356"],"award-info":[{"award-number":["2054356"]}],"id":[{"id":"10.13039\/100000192","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100000001","name":"National Science Foundation","doi-asserted-by":"publisher","award":["1305M221FNEEO0212"],"award-info":[{"award-number":["1305M221FNEEO0212"]}],"id":[{"id":"10.13039\/100000001","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100000001","name":"National Science Foundation","doi-asserted-by":"publisher","award":["2054356"],"award-info":[{"award-number":["2054356"]}],"id":[{"id":"10.13039\/100000001","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>This paper describes, along with some validation results, the one-dimensional variational method (1D-Var) that is in use at the University Corporation for Atmospheric Research (UCAR) to retrieve atmospheric profiles of temperature, pressure, and humidity from the observation of the Global Navigation Satellite System (GNSS) radio occultation (RO). The retrieved profiles are physically consistent among the variables and statistically optimal as regards to a priori error statistics. Tests with idealized data demonstrate that the 1D-Var is highly effective in spreading the observational information and confirm that the method works as designed and expected, provided that correct input data are given. Tests for real-world data sets show that the retrieved profiles agree remarkably well with global weather analyses and collocated high vertical resolution radiosonde observations, and that the 1D-Var can produce value-added retrievals with respect to a priori profiles. We also find that the retrieved profiles are of exceptional long-term stability, suggesting that the 1D-Var can provide an excellent climate data record.<\/jats:p>","DOI":"10.3390\/rs14215614","type":"journal-article","created":{"date-parts":[[2022,11,8]],"date-time":"2022-11-08T08:17:12Z","timestamp":1667895432000},"page":"5614","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":16,"title":["Atmospheric GNSS RO 1D-Var in Use at UCAR: Description and Validation"],"prefix":"10.3390","volume":"14","author":[{"given":"Tae-Kwon","family":"Wee","sequence":"first","affiliation":[{"name":"COSMIC Program, University Corporation for Atmospheric Research, Boulder, CO 80301, USA"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8499-6268","authenticated-orcid":false,"given":"Richard A.","family":"Anthes","sequence":"additional","affiliation":[{"name":"COSMIC Program, University Corporation for Atmospheric Research, Boulder, CO 80301, USA"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2662-4287","authenticated-orcid":false,"given":"Douglas C.","family":"Hunt","sequence":"additional","affiliation":[{"name":"COSMIC Program, University Corporation for Atmospheric Research, Boulder, CO 80301, USA"}]},{"given":"William S.","family":"Schreiner","sequence":"additional","affiliation":[{"name":"COSMIC Program, University Corporation for Atmospheric Research, Boulder, CO 80301, USA"}]},{"given":"Ying-Hwa","family":"Kuo","sequence":"additional","affiliation":[{"name":"COSMIC Program, University Corporation for Atmospheric Research, Boulder, CO 80301, USA"}]}],"member":"1968","published-online":{"date-parts":[[2022,11,7]]},"reference":[{"key":"ref_1","unstructured":"Melbourne, W.G., Davis, E.S., Duncan, C.B., Hajj, G.A., Hardy, K.R., Kursinski, E.R., Meehan, T.K., Young, L.E., and Yunck, T.P. (1994). The Application of Spaceborne GPS to Atmospheric Limb Sounding and Global Change Monitoring, JPL Publication."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"23429","DOI":"10.1029\/97JD01569","article-title":"Observing Earth\u2019s atmosphere with radio occultation measurements using the Global Positioning System","volume":"102","author":"Kursinski","year":"1997","journal-title":"J. Geophys. Res."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"451","DOI":"10.1016\/S1364-6826(01)00114-6","article-title":"A technical description of atmospheric sounding by GPS occultations","volume":"64","author":"Hajj","year":"2002","journal-title":"J. Atmos. Sol. Terr. Phys."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"2547","DOI":"10.5194\/amt-13-2547-2020","article-title":"Consistency and structural uncertainty of multi-mission GPS radio occultation records","volume":"13","author":"Steiner","year":"2020","journal-title":"Atmos. Meas. Tech."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"6","DOI":"10.1038\/s41612-022-00229-7","article-title":"Monitoring global climate change using GNSS radio occultation","volume":"5","author":"Gleisner","year":"2022","journal-title":"npj Clim. Atmos. Sci."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"111","DOI":"10.1002\/asl.169","article-title":"Forecast impact experiment with a constellation of GPS radio occultation receivers","volume":"9","author":"Healy","year":"2008","journal-title":"Atmos. Sci. Lett."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"129","DOI":"10.1002\/asl.173","article-title":"Operational NWP assimilation of GPS radio occultation data","volume":"9","author":"Buontempo","year":"2008","journal-title":"Atmos. Sci. Lett."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"702","DOI":"10.1175\/2008WAF2007070.1","article-title":"Operational implementation of COSMIC observations into NCEP\u2019s global data assimilation system","volume":"23","author":"Cucurull","year":"2008","journal-title":"Wea. Forecast."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"175","DOI":"10.1029\/97RS03183","article-title":"Ionospheric electron density profiles obtained with the Global Positioning System: Results from the GPS\/MET experiment","volume":"33","author":"Hajj","year":"1998","journal-title":"Radio Sci."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"235","DOI":"10.3319\/TAO.2000.11.1.235(COSMIC)","article-title":"COSMIC GPS ionospheric sensing and space weather","volume":"11","author":"Hajj","year":"2000","journal-title":"Terr. Atmos. Ocean. Sci."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"949","DOI":"10.1029\/1999RS900034","article-title":"Analysis and validation of GPS\/MET radio occultation data in the ionosphere","volume":"34","author":"Schreiner","year":"1999","journal-title":"Radio Sci."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"1270","DOI":"10.1016\/j.jastp.2010.08.018","article-title":"Climatology of ionospheric upper transition height derived from COSMIC satellites during the solar minimum of 2008","volume":"72","author":"Yue","year":"2010","journal-title":"J. Atmos. Solar-Terr. Phys."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"29849","DOI":"10.1029\/97JD02400","article-title":"Analysis and validation of GPS\/MET data in the neutral atmosphere","volume":"102","author":"Rocken","year":"1997","journal-title":"J. Geophys. Res."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"2365","DOI":"10.1029\/95GL02127","article-title":"Observing tropospheric water vapor by radio occultation using the Global Positioning System","volume":"22","author":"Kursinski","year":"1995","journal-title":"Geophys. Res. Lett."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"1113","DOI":"10.1029\/2000JD900421","article-title":"A comparison of water vapor derived from GPS occultations and global weather analyses","volume":"106","author":"Kursinski","year":"2001","journal-title":"J. Geophys. Res."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"989","DOI":"10.1175\/1520-0426(1999)016<0989:RSTESA>2.0.CO;2","article-title":"Remotely sensing the Earth\u2019s atmosphere using the Global Positioning System (GPS)\u2014The GPS\/MET data analysis","volume":"16","author":"Feng","year":"1999","journal-title":"J. Atmos. Ocean. Tech."},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Anthes, R., Sjoberg, J., Feng, X., and Syndergaard, S. (2022). Comparison of COSMIC and COSMIC-2 radio occultation refractivity and bending angle uncertainties in August 2006 and 2021. Atmosphere, 13.","DOI":"10.3390\/atmos13050790"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"247","DOI":"10.1111\/j.1365-246X.1967.tb02159.x","article-title":"Numerical Applications of a Formalism for Geophysical Inverse Problems","volume":"13","author":"Backus","year":"1967","journal-title":"Geophys. J. Int."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"309","DOI":"10.3402\/tellusa.v37i4.11675","article-title":"The use of adjoint equations to solve a variational adjustment problem with advective constraints","volume":"37","author":"Lewis","year":"1985","journal-title":"Tellus"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"97","DOI":"10.1111\/j.1600-0870.1986.tb00459.x","article-title":"Variational algorithms for analysis and assimilation of meteorological observations: Theory aspects","volume":"38A","author":"Talagrand","year":"1986","journal-title":"Tellus"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"1311","DOI":"10.1002\/qj.49711347812","article-title":"Variational assimilation of meteorological observations with the adjoint vorticity equation. I: Theory","volume":"113","author":"Talagrand","year":"1987","journal-title":"Quart. J. Roy. Meteor. Soc."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"538","DOI":"10.1175\/1520-0434(1991)006<0538:TNGOAS>2.0.CO;2","article-title":"The new global operational analysis system at the National Meteorological Center","volume":"6","author":"Derber","year":"1991","journal-title":"Wea. Forecast."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"1747","DOI":"10.1175\/1520-0493(1992)120<1747:TNMCSS>2.0.CO;2","article-title":"The National Meteorological Center\u2019s spectral statistical interpolation analysis system","volume":"120","author":"Parrish","year":"1992","journal-title":"Mon. Wea. Rev."},{"key":"ref_24","unstructured":"Eyre, J. (1994). Assimilation of Radio Occultation Measurements into a Numerical Weather Prediction System, ECMWF Tech. Memorandum 199."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"2229","DOI":"10.1175\/1520-0493(1995)123<2229:AOARRU>2.0.CO;2","article-title":"Assimilation of atmospheric radio refractivity using a nonhydrostatic adjoint model","volume":"123","author":"Zou","year":"1995","journal-title":"Mon. Wea. Rev."},{"key":"ref_26","first-page":"3013","article-title":"Use of GPS\/MET refraction angles in three-dimensional variational analysis","volume":"126","author":"Zou","year":"2000","journal-title":"Quart. J. Roy. Meter. Soc."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"19","DOI":"10.1175\/1520-0477(1996)077<0019:GSOTAF>2.0.CO;2","article-title":"GPS Sounding of the Atmosphere from Low Earth Orbit: Preliminary Results","volume":"77","author":"Ware","year":"1996","journal-title":"Bull. Am. Meteorol. Soc."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"313","DOI":"10.1175\/BAMS-89-3-313","article-title":"The COSMIC\/FORMOSAT-3 Mission: Early Results","volume":"89","author":"Anthes","year":"2008","journal-title":"Bull. Am. Meteorol. Soc."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"1015","DOI":"10.1175\/2010BAMS3001.1","article-title":"The NCEP climate forecast system reanalysis","volume":"91","author":"Saha","year":"2010","journal-title":"Bull. Am. Meteorol. Soc."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"1972","DOI":"10.1002\/qj.722","article-title":"Assimilation of Global Positioning System radio occultation data in the ECMWF ERA-Interim reanalysis","volume":"136","author":"Poli","year":"2010","journal-title":"Quart. J. Roy. Meteor. Soc."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"553","DOI":"10.1002\/qj.828","article-title":"The ERA-Interim reanalysis: Configuration and performance of the data assimilation system","volume":"137","author":"Dee","year":"2011","journal-title":"Quart. J. Roy. Meteor. Soc."},{"key":"ref_32","first-page":"1661","article-title":"Retrieving temperature, water vapour and surface pressure information from refractive index profiles derived by radio occultation: A simulation study","volume":"126","author":"Healy","year":"2000","journal-title":"Quart. J. Roy. Meteor. Soc."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"4448","DOI":"10.1029\/2001JD000935","article-title":"1DVAR analysis of temperature and humidity using GPS radio occultation refractivity data","volume":"107","author":"Poli","year":"2002","journal-title":"J. Geophys. Res."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"17513","DOI":"10.1029\/2000JD900151","article-title":"A nonlinear optimal estimation inverse method for radio occultation measurements of temperature, humidity, and surface pressure","volume":"105","author":"Palmer","year":"2000","journal-title":"J. Geophys. Res."},{"key":"ref_35","first-page":"4337","article-title":"One-dimensional variational (1-D Var) retrieval of temperature, water vapor, and a reference pressure from radio occultation measurements: A sensitivity analysis","volume":"108","author":"Nedoluha","year":"2003","journal-title":"J. Geophys. Res."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"17147","DOI":"10.1029\/2001JD900205","article-title":"Application of an optimal estimation inverse method to GPS\/MET bending angle observations","volume":"106","author":"Palmer","year":"2001","journal-title":"J. Geophys. Res."},{"key":"ref_37","doi-asserted-by":"crossref","unstructured":"Rodgers, C.D. (2000). Inverse Methods for Atmospheric Sounding\u2013Theory and Practice, Series on Atmospheric Oceanic and Planetary Physics, 2, World Scientific Publishing Co. Pte. Ltd.","DOI":"10.1142\/9789812813718"},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"1947","DOI":"10.5194\/amt-11-1947-2018","article-title":"A variational regularization of Abel transform for GPS radio occultation","volume":"11","author":"Wee","year":"2018","journal-title":"Atmos. Meas. Tech."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"1054","DOI":"10.1016\/j.proeps.2009.09.162","article-title":"Assessing COSMIC GPS radio occultation derived atmospheric parameters using Australian radiosonde network data","volume":"1","author":"Fu","year":"2009","journal-title":"Procedia Earth Planet. Sci."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"L17807","DOI":"10.1029\/2009GL038712","article-title":"Assessment of radiosonde temperature measurements in the upper troposphere and lower stratosphere using COSMIC radio occultation data","volume":"36","author":"He","year":"2009","journal-title":"Geophys. Res. Lett."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"897","DOI":"10.5194\/acp-9-897-2009","article-title":"Global temperature estimates in the troposphere and stratosphere: A validation study of COSMIC\/FORMOSAT-3 measurements","volume":"9","author":"Kishore","year":"2009","journal-title":"Atmos. Chem. Phys."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"2087","DOI":"10.5194\/amt-4-2087-2011","article-title":"An investigation of atmospheric temperature profiles in the Australian region using collocated GPS radio occultation and radiosonde data","volume":"4","author":"Zhang","year":"2011","journal-title":"Atmos. Meas. Tech."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"30","DOI":"10.1007\/s13131-018-1156-x","article-title":"Comparison of the Arctic upper-air temperatures from radiosonde and radio occultation observations","volume":"37","author":"Chang","year":"2018","journal-title":"Acta Oceanol. Sin."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"D22108","DOI":"10.1029\/2012JD017685","article-title":"Structural evolution of the Madden-Julian Oscillation from COSMIC radio occultation data","volume":"117","author":"Zeng","year":"2012","journal-title":"J. Geophys. Res."},{"key":"ref_45","first-page":"364","article-title":"An approach to predict cyclogenesis using radio occultation observations","volume":"3","author":"Sharma","year":"2013","journal-title":"Int. J. Engg. Innov. Technol."},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"6391","DOI":"10.5194\/acp-13-6391-2013","article-title":"Impact of land convection on temperature diurnal variation in the tropical lower stratosphere inferred from COSMIC GPS radio occultations","volume":"13","author":"Khaykin","year":"2013","journal-title":"Atmos. Chem. Phys."},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"4231","DOI":"10.1002\/jgrd.50369","article-title":"Toward improved corrections for radiation-induced biases in radiosonde temperature observations","volume":"118","author":"Sun","year":"2013","journal-title":"J. Geophys. Res. Atmos."},{"key":"ref_48","doi-asserted-by":"crossref","unstructured":"Iacovazzi, R., Lin, L., Sun, N., and Liu, Q. (2020). NOAA operational microwave sounding radiometer data quality monitoring and anomaly assessment using COSMIC GNSS radio-occultation soundings. Remote Sens., 12.","DOI":"10.3390\/rs12050828"},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"1075","DOI":"10.1175\/2008JTECHA1145.1","article-title":"A new technique for estimation of lower-tropospheric temperature and water vapor profiles from radio occultation refractivity","volume":"26","author":"Jagadheesha","year":"2009","journal-title":"J. Atmos. Ocean. Tech."},{"key":"ref_50","doi-asserted-by":"crossref","first-page":"e1864","DOI":"10.1002\/met.1864","article-title":"Improving the weighted mean temperature model: A case study using nine year (2007\u20132015) radiosonde and COSMIC data in Hong Kong","volume":"27","author":"Xia","year":"2020","journal-title":"Meteorol Appl."},{"key":"ref_51","doi-asserted-by":"crossref","first-page":"925","DOI":"10.3319\/TAO.2021.06.14.01","article-title":"COSMIC-2 radio occultation temperature, specific humidity, and precipitable water in Hurricane Dorian (2019)","volume":"32","author":"Anthes","year":"2021","journal-title":"Terr. Atmos. Ocean. Sci."},{"key":"ref_52","first-page":"602","article-title":"Estimation of the Doppler shift measurements at frequencies used in the NAVSTAR system","volume":"29","year":"1994","journal-title":"Izv. Acad. Sci. Atmos. Oceanic. Phys."},{"key":"ref_53","doi-asserted-by":"crossref","first-page":"1040","DOI":"10.1029\/2002RS002763","article-title":"Full spectrum inversion of radio occultation signals","volume":"38","author":"Jensen","year":"2003","journal-title":"Radio Sci."},{"key":"ref_54","doi-asserted-by":"crossref","first-page":"1819","DOI":"10.1029\/JA073i005p01819","article-title":"On the radio occultation method for studying planetary atmospheres","volume":"73","author":"Phinney","year":"1968","journal-title":"J. Geophys. Res."},{"key":"ref_55","doi-asserted-by":"crossref","first-page":"123","DOI":"10.1086\/111096","article-title":"The neutral atmosphere of Venus as studied with the Mariner V radio occultation experiments","volume":"76","author":"Fjeldbo","year":"1971","journal-title":"Astron. J."},{"key":"ref_56","doi-asserted-by":"crossref","first-page":"1035","DOI":"10.1109\/JRPROC.1953.274297","article-title":"The constants in the equation of atmospheric refractive index at radio frequencies","volume":"41","author":"Smith","year":"1953","journal-title":"Proc. IRE"},{"key":"ref_57","doi-asserted-by":"crossref","first-page":"1177","DOI":"10.1002\/qj.49711247414","article-title":"Analysis methods for numerical weather prediction","volume":"112","author":"Lorenc","year":"1986","journal-title":"Quart. J. Roy. Meteor. Soc."},{"key":"ref_58","first-page":"1367","article-title":"A strategy for operational implementation of 4D-Var, using an incremental approach","volume":"120","author":"Courtier","year":"1994","journal-title":"Quart. J. Roy. Meteor. Soc."},{"key":"ref_59","doi-asserted-by":"crossref","first-page":"195","DOI":"10.3402\/tellusa.v51i2.12316","article-title":"A reformulation of the background error covariance in the ECMWF global data assimilation system","volume":"51A","author":"Derber","year":"1999","journal-title":"Tellus"},{"key":"ref_60","doi-asserted-by":"crossref","first-page":"1971","DOI":"10.1002\/qj.340","article-title":"A review of forecast error covariance statistics in atmospheric variational data assimilation. II: Modelling the forecast error covariance statistics","volume":"134","author":"Bannister","year":"2008","journal-title":"Quart. J. Roy. Meteor. Soc."},{"key":"ref_61","first-page":"706","article-title":"Incremental 4D-Var convergence study","volume":"59A","year":"2007","journal-title":"Tellus"},{"key":"ref_62","doi-asserted-by":"crossref","first-page":"550","DOI":"10.1145\/279232.279236","article-title":"L-BFGS-B: Algorithm 778: L-BFGS-B, FORTRAN routines for large scale bound constrained optimization","volume":"23","author":"Zhu","year":"1997","journal-title":"ACM T. Math. Softw."},{"key":"ref_63","doi-asserted-by":"crossref","unstructured":"Higham, N.J. (2002). Accuracy and Stability of Numerical Algorithms, SIAM. [2nd ed.].","DOI":"10.1137\/1.9780898718027"},{"key":"ref_64","doi-asserted-by":"crossref","first-page":"897","DOI":"10.1175\/1520-0493(2004)132<0897:ATVDAS>2.0.CO;2","article-title":"A Three-Dimensional (3DVAR) data assimilation system for use with MM5: Implementation and initial results","volume":"132","author":"Barker","year":"2004","journal-title":"Mon. Wea. Rev."},{"key":"ref_65","unstructured":"Fisher, M. (2003, January 8\u201312). Background Error Covariance Modeling. Proceedings of the ECMWF Seminar on Recent Developments in Data Assimilation for Atmosphere and Ocean, Reading, UK."},{"key":"ref_66","doi-asserted-by":"crossref","first-page":"507","DOI":"10.2151\/jmsj.2004.507","article-title":"Inversion and error estimation of GPS radio occultation data","volume":"82","author":"Kuo","year":"2004","journal-title":"J. Meteor. Soc. Jpn."},{"key":"ref_67","doi-asserted-by":"crossref","first-page":"2255","DOI":"10.5194\/amt-4-2255-2011","article-title":"Analysis of GPS radio occultation data from the FORMOSAT-3\/COSMIC and Metop\/GRAS missions at CDAAC","volume":"4","author":"Schreiner","year":"2011","journal-title":"Atmos. Meas. Tech."},{"key":"ref_68","doi-asserted-by":"crossref","first-page":"1159","DOI":"10.1029\/90JA02125","article-title":"Extension of the MSIS thermosphere model into the middle and lower atmosphere","volume":"96","author":"Hedin","year":"1991","journal-title":"J. Geophys. Res."},{"key":"ref_69","doi-asserted-by":"crossref","first-page":"12852","DOI":"10.1002\/2013JD019840","article-title":"A noise-aware combination of dual-frequency measurements from GPS radio occultation","volume":"118","author":"Wee","year":"2013","journal-title":"J. Geophys. Res."},{"key":"ref_70","doi-asserted-by":"crossref","first-page":"411","DOI":"10.1029\/96RS03212","article-title":"Sub-Fresnel-scale vertical resolution in atmospheric profiles from radio occultation","volume":"32","author":"Karayel","year":"1997","journal-title":"Radio Sci."},{"key":"ref_71","first-page":"RS6004","article-title":"Comparative analysis of radio occultation processing approaches based on Fourier integral operators","volume":"39","author":"Gorbunov","year":"2004","journal-title":"Radio Sci."},{"key":"ref_72","doi-asserted-by":"crossref","first-page":"111","DOI":"10.1111\/j.1600-0870.1986.tb00460.x","article-title":"The statistical structure of short-range forecast errors as determined from radiosonde data. Part I: The wind field","volume":"38A","author":"Hollingsworth","year":"1986","journal-title":"Tellus"},{"key":"ref_73","unstructured":"Bouttier, F. (1996, January 2\u20136). Application of Kalman filtering to numerical weather prediction. Proceedings of the ECMWF Seminar on Data Assimilation, Reading, UK."},{"key":"ref_74","first-page":"209","article-title":"The statistical structure of forecast errors and its representation in the Met Office global three-dimensional variational data assimilation system","volume":"127","author":"Ingleby","year":"2001","journal-title":"Quart. J. Roy. Meteor. Soc."},{"key":"ref_75","doi-asserted-by":"crossref","first-page":"271","DOI":"10.1093\/comjnl\/15.3.271","article-title":"The JK method: A procedure for finding the eigenvectors and eigenvalues of a real symmetric matrix","volume":"15","author":"Kaiser","year":"1972","journal-title":"Comput. J."},{"key":"ref_76","first-page":"500","article-title":"Formulations for the thermodynamic properties of the saturated phases of H2O from 173.15 K to 473.15 K","volume":"89","author":"Hyland","year":"1983","journal-title":"ASHRAE Trans."},{"key":"ref_77","doi-asserted-by":"crossref","first-page":"1217","DOI":"10.5194\/amt-3-1217-2010","article-title":"Reference Quality Upper-Air Measurements: Guidance for developing GRUAN data products","volume":"3","author":"Immler","year":"2010","journal-title":"Atmos. Meas. Tech."},{"key":"ref_78","first-page":"1777","article-title":"2021: The three-cornered hat method for estimating error variances of three or more atmospheric datasets. Part II: Evaluating recent radio occultation and radiosonde observations, global model forecasts, and reanalyses","volume":"35","author":"Rieckh","year":"2021","journal-title":"J. Atmos. Ocean. Technol."},{"key":"ref_79","doi-asserted-by":"crossref","first-page":"1381","DOI":"10.1002\/qj.864","article-title":"Atmospheric conservation properties in ERA-Interim","volume":"137","author":"Berrisford","year":"2011","journal-title":"Quart. J. Roy. Meteor. Soc."},{"key":"ref_80","doi-asserted-by":"crossref","unstructured":"Anthes, R.A., and Schreiner, W.S. (2019). Six new satellites watch the atmosphere over Earth\u2019s Equator. Eos, 100.","DOI":"10.1029\/2019EO131779"},{"key":"ref_81","doi-asserted-by":"crossref","first-page":"e2019GL086841","DOI":"10.1029\/2019GL086841","article-title":"COSMIC-2 radio occultation-first results","volume":"47","author":"Schreiner","year":"2020","journal-title":"Geophys. Res. Lett"},{"key":"ref_82","doi-asserted-by":"crossref","first-page":"520","DOI":"10.1175\/WAF-D-10-05038.1","article-title":"Revision of convection and vertical diffusion schemes in the NCEP Global Forecast System","volume":"26","author":"Han","year":"2011","journal-title":"Wea. Forecast."},{"key":"ref_83","unstructured":"Campana, K., Caplan, P., Halperin, D.J., Lapenta, B., Lilly, S., Lin, Y., Penny, A.B., Saha, S., Tallapragada, V., and White, G.H. (2019, January 6\u201310). The Development and Success of NCEP\u2019s Global Forecast System. Proceedings of the 99th AMS Meeting, Phoenix, AZ, USA."},{"key":"ref_84","doi-asserted-by":"crossref","first-page":"127","DOI":"10.1007\/s13131-014-0422-9","article-title":"An intercomparison of GPS radiosonde soundings during the eastern tropical Indian Ocean experiment","volume":"33","author":"Xie","year":"2014","journal-title":"Acta Oceanol. Sin."},{"key":"ref_85","doi-asserted-by":"crossref","first-page":"11011","DOI":"10.1002\/2014JD022204","article-title":"Advanced stratospheric data processing of radio occultation with a variational combination for multifrequency GNSS signals","volume":"119","author":"Wee","year":"2014","journal-title":"J. Geophys. Res."},{"key":"ref_86","doi-asserted-by":"crossref","first-page":"D24119","DOI":"10.1029\/2010JD014419","article-title":"Development of a curved ray tracing method for modeling of phase paths from GPS radio occultation: A two-dimensional study","volume":"115","author":"Wee","year":"2010","journal-title":"J. Geophys. Res."},{"key":"ref_87","doi-asserted-by":"crossref","first-page":"4281","DOI":"10.5194\/amt-8-4281-2015","article-title":"A perspective on the fundamental quality of GPS radio occultation data","volume":"8","author":"Wee","year":"2015","journal-title":"Atmos. Meas. Tech."}],"container-title":["Remote Sensing"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-4292\/14\/21\/5614\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T01:11:56Z","timestamp":1760145116000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-4292\/14\/21\/5614"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2022,11,7]]},"references-count":87,"journal-issue":{"issue":"21","published-online":{"date-parts":[[2022,11]]}},"alternative-id":["rs14215614"],"URL":"https:\/\/doi.org\/10.3390\/rs14215614","relation":{},"ISSN":["2072-4292"],"issn-type":[{"value":"2072-4292","type":"electronic"}],"subject":[],"published":{"date-parts":[[2022,11,7]]}}}