Application of quality-controlled sea level height observation at the central East China Sea: Assessment of sea level rise

Abstract. This study presents the state-of-the-art quality control (QC) process for sea level height (SLH) time series observed at the Ieodo Ocean Research Station (I-ROS) in the central East China Sea, a unique in-situ measurement in the open sea for over two decades with a 10-minute interval. The newly developed QC procedure called the Temporally And Locally Optimized Detection (TALOD) method has two notable differences in characteristics from the typical ones: 1) spatiotemporally optimized local range check based on the high-resolution tidal prediction model TPXO9, 2) considering the occurrence rate of a stuck value over a specific period. Besides, the TALOD adopts an extreme event flag (EEF) system to provide SLH characteristics during extreme weather. A comparison with the typical QC process, satellite altimetry, and reanalysis products demonstrates that the TALOD method can provide reliable SLH time series with few misclassifications. Through budget analysis, it was determined that the sea level rise at I-ORS is primarily caused by the barystatic effect, and the trend differences between observations, satellite, and physical processes are related to vertical land motion. It was confirmed through GNSS that ground subsidence of -0.89±0.47 mm/yr is occurring at I-ORS. As a representative of the East China Sea, this qualified SLH time series makes dynamics research possible spanning from a few hours of nonlinear waves to a decadal trend, along with simultaneously observed environmental variables from the air-sea monitoring system in the research station. This TALOD QC method is designed for SLH observations in the open ocean, but it can be generally applied to SLH data from tidal gauge stations in the coastal region.