## 4 Waveform Retracking Results  
Depending on the waveform retracking strategy described in Section 3, 20 hz waveform data of the HY-2B pass 323 and pass 196 have been reprocessed. In this section, we show the along-track raw sea level (RSL) of the reprocessed data and the HY-2B SGDR data. Additionally, some waveform retracking results are illustrated in Figure 11.  
Figure 10: The effective trailing edge search. the \(x\)-axis is the number of gate and the \(y\)-axis is the normalized power of echo, the blue line is real waveform and red line is the effective trailing edge. Figure 9: The distortion of trailing edge judged by the fitting-straight line, the \(x\)-axis is the number of gate and the \(y\)-axis is the normalized power of echo. The blue line is real waveform and green line is the fitting-straight line, the red line circles the distortion. (**a**) the “convex” caused by one distortion of trailing edge against straight line; (**b**) the “concave” caused by two distortions of trailing edge against straight line. The RSL, sea surface height without any range corrections except the instrumental correction, is used to qualitatively analyze the reprocessing results of waveform retracking by comparing with the HY-2B standard SGDR data, and its calculation formula is as follows:  
\[\text{{raw sea level}}=altitude-retracked\ range \tag{6}\]  
where  
\[retracked\ range_{retracking}=tracking\ range+retracking\ range\ correction \tag{7}\] \[+instrumental\ corrections\] \[retracked\ ranges_{S\text{GDR}}=retracking\ range \tag{8}\]  
In the formula, the _tracking range_ corresponds to the variable named _tracker_20 tz_ku_ in SGDR data, the _retracking range correction_ is provided by the reprocessing of waveform retracking mentioned in Section 3, and the _instrumental corrections_ mainly include the three variables named _net_instr_corr_range_ku_, _cog_corr_ and _modeled_instr_corr_range_ku_ in the SGDR data. The _retracking range_ corresponds to the _range_20 tz_ku_ in SGDR data. The comparing results are shown in Figures 12 and 13. Figure 11: The fitting results of real waveforms. Figure 12: The RSL comparisons between the reprocessing results and SGDR data of pass 323 (\(x\)-axis is the along-track latitude, the left \(y\)-axis is the RSL and the right y-axis is the distance from the nominal points of the track to the shoreline illustrated by the black line, the blue line is the SGDR data and red line is the reprocessing results. The light shadow area represents the land; the direction of flight is from 76.5\({}^{\circ}\) to 75.9\({}^{\circ}\)). Figure 13: The RSL comparisons between the reprocessing results and SGDR data of pass 196 (\(x\)-axis is the along-track latitude, the left \(y\)-axis is the RSL and the right \(y\)-axis is the distance from the nominal points of the track to the shoreline illustrated by the black line, the blue line is the SGDR data and red line is the reprocessing results. The light shadow area represents the land and deep shadow area represents the coastal island, the direction of flight is from 120.35\({}^{\circ}\) to 120\({}^{\circ}\)). Figure 12 shows the RSL comparisons of the reprocessing results and the SGDR data in the pass 323. From Figure 12, it can be seen that the RSL of the reprocessing results and the SGDR data have the same trend of sea level change, but the sea surface height of reprocessing results is slightly higher than the SGDR data, which is mainly generated by the waveform noise caused by the circumstances that the trajectory of the pass 323 is parallel to the shoreline. The retracking strategy proposed in this study takes the noise into consideration and addresses this problem by determining the effective trailing edge. Hence, the reprocessing results are affected less. At \(76.05^{\circ}\)E, the distorting waveform caused by the high-energy reflection from coastal 'contamination' leads to a large RSL bias derived from the MLE4 tracker.