Wavenumber correlation analysis of Topex/Poseidon and tide-gauge sea surface heights in the East Sea (Japan Sea)

Sea surface height (SSH) was extracted from the Topex/Poseidon MGDR radar altimeter data in the Fast Sea (Japan Sea) and compared with the SSH estimated from in-situ tide-gauges at Ulleungdo, Pohang, and Sockcho/Mucko sites. Selection criteria such as wet/dry troposphere, ionosphere, and ocean tide were used to enhance the accuracy of SSH. For time series analysis, the one-hour interval tide-gauge SSHs were resampled at 10-day interval of the satellite SSHs. The ocean tide model applied in the altimeter data processing showed periodic aliasings of about 175, 88, 62, 58, 49, and 47 days, and, hence, the 200-day filtering was applied to reduce all these spectral noises. The SSH features showing direct, inverse, and no correlations between the two independent measurements were separated by applying filters in the wavenumber domain of the data sets. The correlation filter passes or rejects wavenumbers as given by the cosine of their phase difference. The original correlation coefficients (CCs) between the satellite and tide-gauge SSHs were 0.46, 0.26, and 0.25, respectively. The CCs were then increased to 0.59, 0.30, and 0.30, respectively, after 200-day filtering, and increased to 0.69, 0.63, and 0.59 after removing inversely correlative components using correlation analysis in the wavenumber domain. The CCs were greatly increased by 87, 227, and 460% when the spectral correlation analysis was followed by 200-day filtering, resulting in the final CCs of 0.86, 0.85, 0.84, respectively.