{"title":"Estimating the observation errors of FY-3C radio occultation dataset using the three-cornered hat method","authors":"Jiman Zhang, Xiaohua Xu, Jia Luo","doi":"10.1007/s44195-023-00054-2","DOIUrl":null,"url":null,"abstract":"Abstract This study uses the three-cornered hat (3CH) method to estimate the observation error variances (ErrVars) of FY-3C RO refractivity, temperature, and specific humidity for the first time. The FY-3C RO data was compared to the three reference datasets including radiosonde observations and NCEP and ERA-Interim reanalyses. The ErrVars of FY-3C RO data are estimated at 18 globally distributed radiosonde stations by using the three reference datasets and are compared to corresponding gridded ErrVars estimated using only the two model datasets as references. The two types of estimates show good correlations at different heights, while the gridded estimates are generally the smaller ones, which may be attributed to the neglection of error correlations among the datasets when applying the 3CH method. Due to the lack of radiosonde data in oceanic and polar regions, the global distributions of FY-3C RO observation errors are presented based on the estimated 5° × 5° gridded ErrVars. The global distribution of the FY-3C RO fractional error standard deviations (ErrSDs) demonstrates that the observation error varies greatly at different pressure levels and latitudes. Specifically, the refractivity ErrSDs at 200 hPa and 50 hPa are significantly higher around 30°N and 30°S than in other areas. The specific humidity ErrSDs generally increase as pressure levels decrease. In addition, statistics show that the fractional ErrSDs of refractivity are generally the lowest between 45° N–75° N and 45° S–75° S at all pressure levels, and land-sea differences exist in the fractional ErrSDs for all three types of RO data.","PeriodicalId":22259,"journal":{"name":"Terrestrial, Atmospheric and Oceanic Sciences","volume":"43 3","pages":"0"},"PeriodicalIF":0.8000,"publicationDate":"2023-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Terrestrial, Atmospheric and Oceanic Sciences","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.1007/s44195-023-00054-2","RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q4","JCRName":"GEOSCIENCES, MULTIDISCIPLINARY","Score":null,"Total":0}
引用次数: 0
Abstract
Abstract This study uses the three-cornered hat (3CH) method to estimate the observation error variances (ErrVars) of FY-3C RO refractivity, temperature, and specific humidity for the first time. The FY-3C RO data was compared to the three reference datasets including radiosonde observations and NCEP and ERA-Interim reanalyses. The ErrVars of FY-3C RO data are estimated at 18 globally distributed radiosonde stations by using the three reference datasets and are compared to corresponding gridded ErrVars estimated using only the two model datasets as references. The two types of estimates show good correlations at different heights, while the gridded estimates are generally the smaller ones, which may be attributed to the neglection of error correlations among the datasets when applying the 3CH method. Due to the lack of radiosonde data in oceanic and polar regions, the global distributions of FY-3C RO observation errors are presented based on the estimated 5° × 5° gridded ErrVars. The global distribution of the FY-3C RO fractional error standard deviations (ErrSDs) demonstrates that the observation error varies greatly at different pressure levels and latitudes. Specifically, the refractivity ErrSDs at 200 hPa and 50 hPa are significantly higher around 30°N and 30°S than in other areas. The specific humidity ErrSDs generally increase as pressure levels decrease. In addition, statistics show that the fractional ErrSDs of refractivity are generally the lowest between 45° N–75° N and 45° S–75° S at all pressure levels, and land-sea differences exist in the fractional ErrSDs for all three types of RO data.
期刊介绍:
The major publication of the Chinese Geoscience Union (located in Taipei) since 1990, the journal of Terrestrial, Atmospheric and Oceanic Sciences (TAO) publishes bi-monthly scientific research articles, notes, correspondences and reviews in all disciplines of the Earth sciences. It is the amalgamation of the following journals:
Papers in Meteorological Research (published by the Meteorological Society of the ROC) since Vol. 12, No. 2
Bulletin of Geophysics (published by the Institute of Geophysics, National Central University) since No. 27
Acta Oceanographica Taiwanica (published by the Institute of Oceanography, National Taiwan University) since Vol. 42.