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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.




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

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}-fv2p1.nc

netCDF Variables

ParameterDescriptionUnitComment
freeboard
freeboard of the sea ice layermeter
freeboard_uncertainty
freeboard uncertaintymeter
latitude
latitude of satellite nadir measurement pointdegrees north
longitude
longitude of satellite nadir measurement pointdegrees east
radar_freeboard
elevation of retracked point above instantaneous sea surface heightmeter

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

meter
radar_mode

radar mode flag

None

flag meaning:

0: pulse limited (lrm)
1: sar
2: sar interferometric

region_code

Region code (adapted from NSIDC region mask with Baltic Sea added)

None

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

kg m-3
sea_ice_density_uncertainty

uncertainty of the sea ice layer density

kg m-3
sea_ice_thickness

thickness of the sea ice layer

meter
sea_ice_thickness_uncertainty

uncertainty of the sea ice layer thickness

meter
sea_ice_type

fraction of multi-year ice

None

Meaning:

0: only first year ice
1: only multi-year ice

sea_ice_type_uncertainty

uncertainty of sea ice classification

None
snow_density

density of the snow layer

kg m-3
snow_density_uncertainty

uncertainty of the snow layer density

kg m-3
snow_depth

thickness of the snow layer

meter
snow_depth_uncertainty

uncertainty of the snow layer thickness

meter
time
UTC timestamp

seconds since 1970-01-01



L3C Grid

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}-fv2p1.nc

with:

tagmeaningexamples
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 




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