The Difference of Sea Level Variability by Steric Height and Altimetry in the North Pacific

Abstract

Sea level variability, which is less than ~100 km in scale, is important in upper-ocean circulation dynamics and is difficult to observe by existing altimetry observations; thus, interferometric altimetry, which effectively provides high-resolution observations over two swaths, was developed. However, validating the sea level variability in two dimensions is a difficult task. In theory, using the steric method to validate height variability in different pixels is feasible and has already been proven by modelled and altimetry gridded data. In this paper, we use Argo data around a typical mesoscale eddy and altimetry along-track data in the North Pacific to analyze the relationship between steric data and along-track data (SD-AD) at two points, which indicates the feasibility of the steric method. We also analyzed the result of SD-AD by the relationship of the distance of the Argo and the satellite in Point 1 (P1) and Point 2 (P2), the relationship of two Argo positions, the relationship of the distance between Argo positions and the eddy center and the relationship of the wind. The results showed that the relationship of the SD-AD can reach a correlation coefficient of ~0.98, the root mean square deviation (RMSD) was ~1.8 cm, the bias was ~0.6 cm. This proved that it is feasible to validate interferometric altimetry data using the steric method under these conditions.

A Simulation Experiment on In-Situ Observation of Short-Wavelength Scale Dynamic Processes and Potential Applications to Wide-Swath Interferometric Altimetry Validation

“…The steric method, which uses SH reconstructed from the temperature and salt profile data observed by the in-situ observation equipment to validate the SSH, is a commonly used method of validation [18]. SH is the height variety between the isobaric surface and the geopotential surface due to changes in density of seawater.…”

“…And a device called "CalNaGeo" is designed that arranges multiple GNSS sensors in a network and drags them behind the ship, which can be used to observe the 2D SSH in a small area and validate the data of the wide-swath area of WIA [17]. Zhang et al [18] verified the consistency between the SH obtained fro m the observation of Argo profile Conductivity-Salinity-Depth (CTD) data and the SSH data on altimeter along -track.…”