###### Abstract  
As an important remote sensing technology, satellite altimetry provides a large amount of observations of sea surface height over the global ocean. In coastal areas, the accuracy of satellite altimetry data decreases greatly due to issues arise in the vicinity of land, related to poorer geophysical corrections and artifacts in the altimeter reflected signals linked to the presence of land within the instrument footprint. To improve the application of HY-2B altimetry data in coastal areas, this study proposes a coastal waveform retracking strategy for HY-2B altimetry mission, which depends on the effective trailing edge and the leading edge, which are less affected by coastal 'contamination', to retrieve accurate waveform information. The HY-2B pass 323 and pass 196 data are reprocessed, and the accuracy of the reprocessing results in the range of 0-40 km offshore is validated against the tide gauge data and compared with the HY-2B standard SGDR data. According to the analysis conclusion, the accuracy of the reprocessed data is higher than that of the SGDR data and has good performance within 15 km offshore. For the pass 323, the mean value of correlation coefficient and RMS of the reprocessed data against the corresponding tide gauge data are 0.893 and 451.5 cm, respectively, in the range within 0-15 km offshore, and are 0.86 and 33.6 cm, respectively, in the range beyond 15 km offshore. For the pass 196, the mean value of correlation coefficient and RMS of the reprocessed data against the corresponding tide gauge data in the range within 0-12 km offshore are 0.84 and 33.0 cm, respectively, and in the range within 0-5 km offshore to the island are 0.90 and 29.3 cm, respectively, and in the range beyond 5 km offshore to the island are 0.92 and 36.2 cm, respectively, which are all better than the corresponding values of the SGDR data, especially in the range closed to the land. The results indicate that the proposed coastal waveform retracking strategy for HY-2B altimetry greatly improves the quality of HY-2B altimetry data in coastal areas. HY-2B Satellite; altimetry; waveform retracking; coastal areas 202214502660  
To correct the deviation of standard range measurement provided by the on-board tracker, a necessary process called 'waveform retracking' is applied to provide the tracking range correction, significant wave height, and backscatter coefficient correction. The principle of waveform retracking is inversing the sea surface information from the waveform data based on the waveform model. Depended on microwave scattering theory, scholars have described the waveform using the [PERSON] theoretical ocean model (referred to as the [PERSON] model), which was proposed by [PERSON] and refined by [PERSON] [1,2]. The [PERSON] model expounds the ideal relationship between the pulse signal traveling time and the pulse energy reflected from the sea surface: an increasing leading edge and a decreasing trailing edge with a certain amount of thermal noise, as shown in Figure 1. In Figure 1, the midpoint of the leading edge, which is known as the'mid-power point', is used to estimate the distance between the satellite altimeter and the sea surface. The increasing time of leading edge is mainly dependent on the significant wave height (SWH) at the nadir, with a longer increasing time associated with a larger SWH. The amplitude of the echo can be converted into a measurement of the backscatter coefficient \(\sigma^{0}\) on the basis of the instrument calibration. The slope of the trailing edge depends on the antenna mispointing angle, which is approximately 0.3\({}^{\circ}\). The precision of waveform retracking largely depends on the quality of altimetry waveform data, usually, the waveform data observed on the open ocean is the best, which is reflected by the pure-water surface and contains stable noise information. According to different areas, waveform retracking can be divided into waveform retracking for polar, open ocean, and coastal areas.