The Effects of Differential Tropospheric Error on the Measurement of Wide-Swath Interferometric Altimetry

Tropospheric path delay (TPD) is one of the primary factors affecting the accuracy of sea level anomaly (SLA) measurements by satellite altimetry. This article focuses on the effects of differential tropospheric error (DTE), resulting from the different TPD between two antennas with different incident angles in the cross-track direction of the wide-swath interferometric altimetry (WSIA). Based on the principle of interferometry, this article presents the mathematical model of the DTE and conducts a simulation experiment for validation, demonstrating a tangent-squared of incidence angles relationship between the DTE and TPD. Combining observational parameters of the SWOT and Guanlan satellites, the DTE increases nonlinearly from the near nadir, reaching approximately 1 and 3 cm at the far end of the swath for SWOT and Guanlan satellites, respectively. In addition, a comparison of relative magnitude between the SLA and DTE is carried out by computing the root mean square (rms) values using the wavenumber spectrum. The ratio of rms values is larger in the typical strong current regions [Kuroshio, Gulf Stream, and Antarctic Circumpolar Current (ACC)], while smaller in the low-latitude tropics regions. Furthermore, the global distribution of the power ratio is analyzed by calculating the ratio of spectral densities between the SLA and DTE at different wavelengths. The ratio of power is largest at mesoscale (250 km) and gradually homogeneous over the global ocean at submesoscale (50 km).