5.8. L2P SAR WV & IW/EW by DLR#
The SAR L2P products are:
along-track files for S1 wave mode WV (averaged values for each 20x20 km imagette acquired each 100 km)
sea state rastered fields with mesh of 5 km for S1 IW and 17.5 km for S1 EW.
5.8.1. L2P SAR geophysical data record format specification#
The Table provides an overview of the CCI Sea State L2P environment (geophysical) data record within a L2P file (DLR_OCN).
Abb. in netCDF product |
Description in netCDF product |
Unit/Meaning |
|
|---|---|---|---|
total significant wave height |
swh |
total C band significant wave height |
m |
mean wave period Tm0-1 |
Tm0 |
C band Mean wave period |
s |
first moment wave period |
Tm1 |
C band First moment period |
s |
second moment wave period |
Tm2 |
C band Second moment period |
s |
wave height swell dominant system |
swell_swh_primary |
C band Dominant swell wave height |
m |
wave height swell secondary system |
well_swh_secondary |
C band Secondary swell wave height |
m |
significant wave height windsea |
windwave_swh |
C band Windsea wave height |
m |
mean period windsea |
windwave_period |
C band Windsea wave period |
s |
quality flag |
swh_quality |
quality of C band SAR significant wave height measurement |
0=undefined (e.g. land), 1=bad, 2=acceptable (not used), 3 – good |
rejection flag |
swh_rejection_flags |
consolidated Significant Wave height quality flags |
1=Nv (variance) > max (not more used), 2=swh outlier, 4=invalid value, 8=wind below 2 m/s (not more used), 16=not_water (land) |
uncertainty SWH |
swh_uncertanty |
best estimate of significant wave height standard error |
to MFWAM (CMEMS) estimated for each swh domains 0-1.5 m, 1.5-3m, 3-6m, >6m and interpolated/extrapolated |
uncertainty SW1 |
swell_swh_primary_uncertanty |
Best estimate of dominant swell wave height standard error |
to MFWAM (CMEMS) estimated for each swh domains 0-1.5 m, 1.5-3m, 3-6m, >6m and interpolated/extrapolated |
uncertainty SW2 |
swell_swh_secondary_uncertanty |
Best estimate of secondary swell wave height standard error |
to MFWAM (CMEMS) estimated for each swh domains 0-1.5 m, 1.5-3m, 3-6m, >6m and interpolated/extrapolated |
uncertainty SWW |
windwave_swh_uncertanty |
Best estimate of windsea wave height standard error |
to MFWAM (CMEMS) estimated for each swh domains 0-1.5 m, 1.5-3m, 3-6m, >6m and interpolated/extrapolated |
uncertainty Tm0 |
Tm0_uncertanty |
Best estimate of mean wave period standard error |
to MFWAM (CMEMS) estimated for each swh domains 0-4 s, 4-7 s, 7-10s, >10 s and interpolated/extrapolated |
uncertainty Tm1 |
Tm1_uncertanty |
Best estimate of first moment wave period standard error |
to WW3 estimated for each swh domains 0-4 s, 4-7 s, 7-10s, >10 s and interpolated/extrapolated |
uncertainty Tm2 |
Tm2_uncertanty |
Best estimate of second moment wave period standard error |
to MFWAM (CMEMS) estimated for each swh domains 0-4 s, 4-7 s, 7-10s, >10 s and interpolated/extrapolated |
uncertainty Tmw |
windwave_period_uncertanty |
Best estimate of mean period windsea standard error |
to MFWAM (CMEMS) estimated for each swh domains 0-4 s, 4-7 s, 7-10s, >10 s and interpolated/extrapolated |
5.8.2. L2P SAR quality_level#
The DLR algorithm SAR-SeaStaR is optimised for minimizing the percenatge of the non-valid data. For example, the number of non-valid ocean imagettes for S1 WV is ca. 1.5% with an accuracy of ca. 0.26 m in terms of SWH. This optimization allows processing data for ambiguous enviroment conditions dominate in coastal ares (NRCS artifacts by ships, buoys, watermarks, windparks, etc.) and by low winds under 2 m/s.
Due to series of control procedures, rejection has been inicialized:
=0 - undefined (e.g. land)
=1 - bad
=2 - acceptable (not used),
=3 - good
5.8.3. L2P SAR rejection_flags#
=1 - variance > max (not more used)
=2 - swh outlier, non-valid
=4 - non-valid value
=8 - valid value, wind below 2 m/s (not more used)
=16 - not_water (land), correspondes to quality_level=0 (land)