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Distributed data processing levels are the daily trajectory summary (l2p) and weekly/monthly gridded data (l3c). The content of products based on the near-real time and reprocessed input version are identical and marked by the timeliness tag in the filename and global attributes of the netCDF files.
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NetCDF File Format
Data in netCDF format is self describing and bundles geophysical variables as well as metadata in a file format that can be easily read by different programming languagues and tools. We use v4 of the netCDF format that supports compression of its content to minimize file sizes.
Global Attributes
The global attributes of the netCDF file provide metadata such as citation, reference, time coverage and more. Use ncinfo filename.nc
or tools like panoply to list the global attributes.
L2P Trajectory
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The Level-2 pre-processed (l2p) product contains daily information from CryoSat-2 at full resolution (see documentation).
Filenaming
The filename of l2p data indicated the timelines (nrt or ntc) and the date (e.g. 20181001) of the data file:
awi-siral-l2p-sithick-cryosat2-{timeliness}-nh-{year}{month}{day}-fv2p4.nc
netCDF Variables
f{version}.nc
freeboard
freeboard_uncertainty
latitude
longitude
radar_freeboard
radar freeboard is defined as the elevation basedon the assumption of vacuum light speed without a snow propagation or range penetration correction
radar_freeboard_uncertainty
algorithm uncertainty (error propagation) of the radar freeeboard retrieval
radar_mode
radar mode flag
flag meaning:
0: pulse limited (lrm)
1: sar
2: sar interferometric
region_code
Region code (adapted from NSIDC region mask with Baltic Sea added)
New in version 2.1
flag meaning:
0: Inland sea and lakes
1: Ice-free Oceans
2: Sea of Okhotsk
3: Bering
4: Hudson Bay
5: St John
6: Baffin Bay
7: East Greeland Sea
8 Barents Sea
9: Kara Sea
10: Laptev Sea
11: East Siberian Sea
12: Chukchi Sea
13: Beaufort Sea
14: Canadian Islands
15: Central Arctic
16: Baltic Sea
20: land
21: land outline
sea_ice_density
density of the sea ice layer
sea_ice_density_uncertainty
uncertainty of the sea ice layer density
sea_ice_thickness
thickness of the sea ice layer
sea_ice_thickness_uncertainty
uncertainty of the sea ice layer thickness
sea_ice_type
fraction of multi-year ice
Meaning:
0: only first year ice
1: only multi-year ice
sea_ice_type_uncertainty
uncertainty of sea ice classification
snow_density
density of the snow layer
snow_density_uncertainty
uncertainty of the snow layer density
snow_depth
thickness of the snow layer
snow_depth_uncertainty
uncertainty of the snow layer thickness
time
seconds since 1970-01-01
L3C Grid
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The Level-3 collated (l2p) product contains information from CryoSat-2 at a space-time grid (see documentation).
Filenaming
The filename of l2p data follows the pattern:
awi-siral-l3c-sithick-cryosat2-{timeliness}-{grid_id}-{period}-fv2p1f{version}.nc
with:
tag | meaning | examples |
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timeliness | The timeliness of the CryoSat-2 input data | nrt, ntc |
grid_id | An identifier string that describes the characteristics of the grid. Usually indicates the hemisphere, spatial resolution and projection of the grid. | nh_25km_ease2 |
period | A string that either indicates the period or the range of time coverage. E.g. yyyymm for monthly, or start to end separated by "_" with start and end in format of yyyymmdd. | 201804, 20180101_20180107 |
version | Algorithm version str | v2p6 |