Editorial: Application of Satellite Altimetry in Marine Geodesy and Geophysics

The satellite altimetry concept was first proposed in 1969. Since then, many satellite altimetry missions have been implemented. With the development of the satellite altimetry technique, altimetry modes have been created for ocean and land observations, such as the traditional pulse-limited radar, the synthetic aperture radar (SAR), the laser mode, the three-dimensional imagingmode, and the global navigation satellite system refection (GNSS-R)mode. Figure 1 gives an overview of all satellite altimetry missions. China also developed the ocean dynamic environment satellite missions, HY-2A/2B/2C/2D. These three missions (HY-2B/2C/2D) are currently simultaneously collecting global marine information and monitoring changes in ocean states. Altimeter data quality may be affected by an error in instruments, atmospheric delay, sea state bias, geophysical environment correction (e.g., solid earth tide correction, ocean tide correction, inverse barometric effect, etc.), and precise orbit determination, The coastal waveforms may be seriously contaminated by the land and seabed. Therefore, these systematic errors should be corrected and presented in geophysical data records (GDRs). Researchers can then apply alternative correction models and new waveform retracking algorithms to further improve the quality of satellite altimetry data. Radar altimetry missions include the exact repeat mission (ERM) and the geodetic mission (GM). The oceanic environment can be continuously monitored with ERM data. The GM data are mainly used to study marine geodesy and geophysics. Laser altimeter, SAR altimeter, and three-dimensional imaging altimeter collect massive ocean data. Once fused, multi-source altimeter data can provide high-resolution and precise ocean information. In marine geodesy, geophysics, and oceanography, altimeter data have been used in several studies including marine gravity, geoid, mean sea surface, mean dynamic topography, sea levels rising, ocean currents, geostrophic, sea wind, and wave, bathymetry, and seabed tectonics. This Research Topic includes 17 papers in the field of satellite altimeter data processing, exploring applications to marine geodesy and geophysics. A summary of these papers is given below.