V2.0.1 changes

Basic, Expert

MDT and absolute derivatives near the coasts

Due to a change in the MDT/MDU/MDV interpolator in the V2.0.0 (switched to bicubic), some points near the coast have been lost with respect to the V1.0.2.

In order to mitigate this issue, the source grids for MDT/MDU/MDV are filled using a Gaussian-Seidel method. This prevents the loss of points in the mdt, ugos and vgos fields.

../../_images/changes_2.0.1_absolute_speeds.png

Wrong flag application in eclipses

The editing flag was wrongly applied on the sea surface height in the netcdf products. Although the eclipses where present in the ssha_unedited field, they were wrongly removed in the ssha_unfiltered and ssha_filtered field. This has been fixed and the eclipse data is properly available as annonced in the V2.0 change note

../../_images/changes_2.0.1_eclipses.png

Unsmoothed

Flagging changes

Land-sea mask

In V1.0, we introduced a mask that fixes most of the known L2 issues. This mask was used in the Basic and Expert datasets but not in the Unsmoothed dataset. V2.0.1 now aligns the land/sea masks of all 3 datasets by using this mask in the Unsmoothed product. Note that the patch improvement introduced in V2.0 is also applied

Sea-ice leads flagging

LEGOS has developed a sea-ice classification for polar areas. It provides several information:

  • ocean (flag #0)

  • ocean_unsure (flag #18)

  • ice_unsure (flag #19)

  • ice (flag #20)

Summer in the Arctic (May-September) is still exploratory because of the presence of melt-pounds on the sea ice. As this product is experimental, a few imperfections have been identified.

Some passes contain mostly unsure categories

../../_images/classification_unsure.png

Cycle 484 Pass 9

Along-track lines due to radiation hits (more details here ) may be visible and deteriorate the classification

../../_images/classification_radiation_hits.png

Cycle 577 Pass 24

Ice classification is only applied when the ice concentration exceeds 50%. Between 0 and 50% of ice concentration, the data is automatically edited with flag #20

../../_images/classification_ice_concentration_threshold.png

Cycle 500 Pass 1

Finally, denoising is available for leads. It only seems relevant when the sea-ice classification is correct

../../_images/classification_denoised.png

Cycle 507 Pass 1

Product content

New variables

  • cross_track_distance was missing in the Unsmoothed files. It is now available in the netcdf products.

Basic, Expert and Unsmoothed

Manual editing of problematic half orbits

Some half orbits of the calval phase are not well calibrated and were not properly detected by the editing algorithm. The quality flag of these half orbits has been set to 30 to mark them as bad:

Newly edited half orbits (ranges are inclusive)

Cycle 567

[20-28]

Cycle 568

[1-7], [10-13]

Product content

For clarity purpose, some variables have been renamed in the product. Note that this renaming only affects V2.0.1: the old names are still in use for V2.0

Renamed variables

  • ugos -> ugos_filtered

  • vgos -> vgos_filtered