Abstract
The first Chinese altimetry satellite, Haiyang-2A (HY-2A), which was launched in 2011, has provided a large amount of sea surface heights which can be used to derive marine gravity field. This paper derived the vertical deflections and gravity disturbances using HY-2A observations for the major area of the whole Earth’s ocean from 60°S and 60°N. The results showed that the standard deviations (STD) of vertical deflections differences were 1.1 s and 3.5 s for the north component and the east component between HY-2A’s observations and those from EGM2008 and EIGEN-6C4, respectively. This indicates the accuracy of the east component was poorer than that of the north component. In order to clearly demonstrate contribution of HY-2A’s observations to gravity disturbances, reference models and the commonly used remove-restore method were not adopted in this study. Therefore, the results can be seen as ‘pure’ signals from HY-2A. Assuming the values from EGM2008 were the true values, the accuracy of the gravity disturbances was about −1.1 mGal in terms of mean value of the errors and 8.0 mGal in terms of the STD. This shows systematic errors if only HY-2A observations were used. An index of STD showed that the accuracy of HY-2A was close to the theoretical accuracy according to the vertical deflection products. To verify whether the systematic errors of gravity field were from the long wavelengths, the long-wavelength parts of HY-2A’s gravity disturbance with wavelengths larger than 500 km were replaced by those from EGM2008. By comparing with ‘pure’ HY-2A version of gravity disturbance, the accuracy of the new version products was improved largely. The systematic errors no longer existed and the error STD was reduced to 6.1 mGal.
Highlights
Satellite altimetry plays a significant role in Earth science, such as marine gravity field recovery [1,2,3,4,5,6], ocean current inversion [7,8,9], seafloor topography estimation [10,11], geological interpretations [12,13,14,15], and so on
These results indicate that HY-2A data can be used for Earth science research as other altimetry satellites
In order to quantify the differences, the vertical deflections derived from HY-2A data and their equivalents from EGM2008 and EIGEN-6C4 were compared
Summary
Satellite altimetry plays a significant role in Earth science, such as marine gravity field recovery [1,2,3,4,5,6], ocean current inversion [7,8,9], seafloor topography estimation [10,11], geological interpretations [12,13,14,15], and so on. As the first altimetry satellite developed by China, HY-2A (Haiyang-2A) was launched in 2011, and in 2016 its orbit was changed for conducting geodetic applications, i.e., marine gravity inversion. Jiang et al [18] reprocessed the SSH measurements from HY-2A radar altimeter and the STD of the crossover SSH differences for HY-2A was around 4.53 cm, which was largely improved when compared to that of HY-2A Interim Geophysical Data Record (IGDR) product. Zhang et al [19] proved that HY-2A results were at a comparable level with respect to other missions like Jason-1 and CryoSat-2. These results indicate that HY-2A data can be used for Earth science research as other altimetry satellites
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