Estimating the observation errors of FY-3C radio occultation dataset using the three-cornered hat method

IF 0.8 4区 地球科学 Q4 GEOSCIENCES, MULTIDISCIPLINARY
Jiman Zhang, Xiaohua Xu, Jia Luo
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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.
利用三角帽法估计FY-3C射电掩星数据集的观测误差
摘要本文首次采用三角帽(3CH)方法估算了FY-3C RO折射率、温度和比湿的观测误差方差(ErrVars)。将FY-3C RO数据与探空观测、NCEP和ERA-Interim再分析等3个参考数据集进行了比较。使用三个参考数据集估算了全球分布的18个探空站FY-3C RO数据的ErrVars,并与仅使用两个模型数据集作为参考数据集估算的相应网格化ErrVars进行了比较。这两种估计在不同高度都表现出良好的相关性,而网格化估计通常是较小的估计,这可能是由于在应用3CH方法时忽略了数据集之间的误差相关性。由于海洋和极地地区缺乏探空资料,基于估算的5°× 5°栅格errvar,给出了FY-3C RO观测误差的全球分布。风云3c RO分数误差标准偏差(errsd)的全球分布表明,不同气压水平和纬度的观测误差差异较大。其中,200 hPa和50 hPa的折射率errsd在30°N和30°S附近明显高于其他地区。比湿度errsd通常随着压力水平的降低而增加。此外,统计结果表明,在所有压力水平下,45°N - 75°N和45°S - 75°S之间折射率errsd分数值最低,且三种RO资料的errsd分数值存在海陆差异。
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来源期刊
CiteScore
2.00
自引率
0.00%
发文量
29
审稿时长
4.5 months
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.
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