- Created by Stefan Hendricks, last modified on Oct 28, 2018
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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
| Parameter | Description | Unit | Comment |
|---|---|---|---|
freeboard | freeboard of the sea ice layer | meter | |
freeboard_uncertainty | freeboard uncertainty | meter | |
latitude | latitude of satellite nadir measurement point | degrees north | |
longitude | longitude of satellite nadir measurement point | degrees east | |
radar_freeboard | elevation of retracked point above instantaneous sea surface height | meter | 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) |
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 |
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 |
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
where:
| tag | meaning | examples |
|---|---|---|
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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