October 31, 2024

This new version 02 has an additional 2 months of SWOT data.

September 24, 2024

This is the first gravity version 01 based on SWOT altimetry.  We processed the SWOT data by first removing 
north and east slopes from the V32 model. The residual SWOT data were block medianed at 1 minute, voids 
were padded with zeros, and then all the data were gridded with surface.

These are residual slopes with respect to V32 gravity so the V32 gravity was added back to all the products.  
The SWOT data include all the data for the 1-day repeat and 18 cycles of the 21-day repeat processed by 
Yao Yu on July 25, 2024.

The 32 version includes an additional 12 months of Altika, Cryosat LRM, Cryosat SAR and Sentinel-3A/B.
Waveform retracking was performed on the following altimeter data Jason-1/2, Envisat, Altika, and Cryosat-LRM.
This was done to reduce the wavelength of the SWH smoothing filter from 45 km to 30 km.  In addition, we solved
for the optimal sea state bias for all the altimeters to reduce the SWH noise in the > 30 km wavelength band.
Finally, we implemented a mask to remove all data within 3 km of any land.  This helps to reduce land-contaminated
waveforms.  A precise land mask has been applied to all products to further reduce land/ocean edge effects.

A description of each file follows.

curv_SWOT_01.img - ocean surface curvature = vertical gravity gradient (VGG), Eotvos * 10, read with img2grd only
curv_SWOT_01.nc  - ocean surface curvature = vertical gravity gradient (VGG), Eotvos, netcdf, lon-lat coordinates
grav_SWOT_01.img - free-air gravity anomaly, milliGal * 10, read with img2grd only
grav_SWOT_01.nc  - free-air gravity anomaly, milliGal, netcdf, lon-lat coordinates
east_SWOT_01.img - deflection of the vertical = sea surface slope, microradian * 10, read with img2grd only
east_SWOT_01.nc  - deflection of the vertical = sea surface slope, microradian, netcdf, lon-lat coordinates
north_SWOT_01.img - deflection of the vertical = sea surface slope, microradian * 10, read with img2grd only
north_SWOT_01.nc  - deflection of the vertical = sea surface slope, microradian, netcdf, lon-lat coordinates
make_NETCDF.com - example of how to translate the img files to netcdf
src_img - source code for reading the img files in fortran or C