Supporting information Text S2.
The first step is to retrack the raw SGDR waveforms from Jason-1 and
Jason-2 altimeter missions using a two-pass waveform retracker (Sandwell
et al. 2014). The second step is to low-pass filter and resample the
20-Hz retracked height into ~5 Hz, to enhance the signal
to noise. The third step is to correct the retracked height using state
of the art geophysical and range corrections (Andersen and Scharroo,
2011). The fourth step is to perform outlier editing through comparing
height and along-track slopes with the associated heights and along
track slopes from EGM2008 as described by Zhang et al., (2020). The
fifth step is to remove the slopes of the EGM2008 geoid and the slopes
of the Mean Dynamic Topography (DOT_min1x1_EGM08) associated with the
EGM2008 geoid) and to apply a low-pass filter in order to obtain
along-track filtered sea surface height gradients.
Finally, the along-track sea surface slopes were turned into residual
vertical deflections and then residual gravity anomalies. Subsequently
the marine gravity anomalies at 1’×1’ resolution were then computed by
restoring the EGM2008 gravity field associated with the EGM2008 geoid
model (Zhang et al., 2017).
References
Pavlis, N. K., Holmes, S. A., Kenyon, S. C., & Factor, J. K. (2012),
The development and evaluation of the Earth Gravitational Model 2008
(EGM2008), J. Geophys Res , D. 117, B4,
https://doi.org/10.1029/2011JB008916
Sandwell, D. T., Dietmar-Müller R., Smith W.,Garcia, E. & Francis, R.
(2014), New global marine gravity model from CryoSat-2 and Jason-1
reveals buried tectonic structure. Science . 346 no. 6205 pp.
65-67
Sandwell, D. T., and W. H. F. Smith (2005), Retracking ERS‐1 altimeter
waveforms for optimal gravity field recovery, Geophys. J. Int., 163,
79– 89, doi:10.1111/j.1365‐246X.2005.02724.x
Zhang, S., Andersen, O., Kong X., & Li H., (2020), Inversion and
Validation of Improved Marine Gravity Field Recovery in South China Sea
by Incorporating HY-2A Altimeter Waveform Data. Remote Sensing ,
12(5), 802. https://doi.org/10.3390/rs12050802.
Zhang S., Sandwell D., Jin T., & Li D., (2017), Inversion of Marine
Gravity Anomalies over Southeastern China Seas from Multi-Satellite
Altimeter Vertical Deflections. J of Applied Geophysics , 137,
128-137.