Contributors: Lin Gilbert (University of Leeds), Sebastian B. Simonsen (Technical University of Denmark)
Issued by: University of Leeds / Lin Gilbert
Date:
Ref: C3S2_312a_Lot4.WP2-FDDP-IS-v1_202212_SEC_PUGS-v4_i1.1
Official reference number service contract: 2021/C3S2_312a_Lot4_EODC/SC1
History of modifications
List of datasets covered by this document
Related documents
Acronyms
General definitions
| Term | Definition |
|---|---|
| Backscatter: | The portion of the outgoing radar signal that the target redirects directly back toward the radar antenna. |
| Baseline: | A combination of processor versions, auxiliary data and other needed enablers that allows the generation of a coherent set of Earth observation products. |
| Bias: | The tendency of an instrument to preferentially make measurements over a certain type of surface. |
| Climate Data Record (CDR): | A time series of measurements of sufficient length, consistency and continuity to determine climate variability and change. |
| Crossover analysis: | A method for deriving elevation change at locations where the orbits of a single or multiple satellites cross. |
| Cross-calibration: | A method that merges datasets from multiple satellites into one consistent dataset. |
| Key performance indicator: | A quantifiable measure used to evaluate the success of a product in meeting its performance objectives. |
| Laser altimeter: | An instrument mounted on an aircraft or spacecraft that measures altitude from the ground surface below by timing how long it takes a pulse of laser light to travel to ground, reflect, and return to the craft. |
| Radar Altimetry: | Radar altimetry measures height of a satellite or aircraft above a land or ocean surface by timing how long it takes a pulse of radio waves to travel to the surface below, reflect, and return to the craft. |
| Stereographic | Stereographic is a planar perspective projection, viewed from the point on the globe opposite the point of tangency. |
| Stability: | An estimate of the consistency of the measurements over time. |
| Surface Elevation Change (SEC): | The surface elevation of a point on an ice sheet is the height of the ice sheet surface above a reference geoid (a hypothetical solid figure whose surface corresponds to mean sea level and its imagined extension under land areas). In crease in surface elevation over time at a given location indicates a gain of ice or snow at that location, and conversely decrease indicates a loss. The surface elevation change product provides the rate of change given at monthly intervals at each location on a grid covering the ice sheet. The definition of the grid projection includes the geoid used. Given the rates of change, absolute change can be calculated for any time period. |
Tracking: | Retrieving the radar echo from a given radar pulse. |
Uncertainty: | An estimate of the error in a measurement, due to limitations in the measuring instrument or statistical fluctuations in the quantity being measured. |
Validation: | Comparison between two independent datasets to test their agreement. |
Scope of the document
This document is the Product User Guide and Specification for the ice sheet surface elevation change (SEC) products, part of the Copernicus Ice Sheets and Ice Shelves service. It describes the datasets produced, and their specifications.
The service addresses three essential climate variables (ECVs) by providing four separate products.
- Ice velocity is given for Greenland in product WP2-FDDP-IV-CDR
- Gravimetric mass balance is given for Greenland and Antarctica in product WP2-FDDP-GMB-CDR5
- Surface elevation change is given for:
- Antarctica in product WP2-FDDP-SEC-CDR-AntIS
- Greenland in product WP2-FDDP-SEC-CDR-GrIS
Executive summary
We document here the description of each of the Climate Data Records (CDRs) v4.0 for the two Polar region SEC products, with a guide to their usage and specifications.
In section 1 (for Antarctica) and section 2 (for Greenland) we describe the products and their inputs, update schedules and validations. We list the target requirements for data quality. We tabulate the contents of the data product files, explain known issues with the dataset, and describe the file-naming conventions used. The data files are produced in netCDF format, and we give examples of their structure and metadata contents.
In section 3 we give details of public access to the products, licencing, and how to make enquiries about them.
Product Change Log
The same product changes are applicable to both Antarctic and Greenland products.
Version | Product Changes |
V1 | Initial product, using data from ERS1, ERS2, EnviSat and CryoSat-2. |
V2 | Data from Sentinel-3A added. |
V3 | Data from Sentinel-3B added. |
| V4 | Updated timeseries and revised filtering of raw data. |
1. Surface elevation change, Antarctica – WP2-FDDP-SEC-CDR-AntIS
1.1. Product description
The product contains surface elevation change (SEC) rates and their uncertainties from the Antarctic ice sheet, ice shelves, ice rises, and islands on a regular geographic grid at regular (monthly) time intervals. The change rate is calculated over a 5-year period. An example plot from one data grid is shown in Figure 1 below.
Figure 1: Example data from Antarctic surface elevation change product WP2-FDDP-SEC-CDR-AntIS for the 5-year period from May 2007 to May 2012.
The current version 4.0 of the CDR product builds on the legacy of its preceding versions:
CDRv1. The initial product release builds on the R&D efforts of the Antarctic ice sheet Climate Change Initiative (CCI) project’s surface elevation measurements from the European Remote-sensing Satellite (ERS)1, ERS2, Envisat and CryoSat-2.
CDRv2. Adds the use of observations from Sentinel-3A.
CDRv3. The time series have been reprocessed, with the upgraded baselines for Envisat and CryoSat-2 data and with the inclusion of data from Sentinel-3B.
CDRv4. The time series have been reprocessed, with the upgraded data filtering.
The product is updated monthly (as an Interim Climate Data Recor: ICDR). Due to the processing of the data, there is a time lag of 2 months between the acquisition of new measurements and their addition to the product. The product specifications are summarised in Table 1.
Table 1: Antarctic SEC product specification summary
| Specification | Description |
|---|---|
| Sensors | ERS1 and ERS2 RA: https://earth.esa.int/eogateway/instruments/ra-ers/description Envisat RA-2: https://earth.esa.int/eogateway/instruments/ra2 Cryosat-2 SIRAL: https://earth.esa.int/eogateway/instruments/siral/description Sentinel-3A and Sentinel-3B SRAL: https://sentinels.copernicus.eu/web/sentinel/technical-guides/sentinel-3-altimetry/instrument/sral |
| Grid | 25km by 25km polar stereographic projection based on 0°E, 71°S on the WGS84 ellipsoid (EPSG: 3031) |
| Time range | 1992 to 2 months before present |
| Time intervals | 5yr window moving in monthly steps |
| Validation frequency | Annual |
| Quality flagging | Flags provided for steep terrain and missing data |
Validation is performed with respect to observation campaigns by the Airborne Topographic Mapper, a scanning laser altimeter flown on board aircraft by Operation IceBridge (Studinger 2014), mission webpage at https://nsidc.org/data/icebridge. Each campaign lasts for one Antarctic spring season (October to December), and so validation is performed annually. The same Operation IceBridge validation has been performed for each version of the product, but new to v4.0 is a second validation against ICESat-2's satellite-mounted laser altimeter, mission webpage at https://nsidc.org/data/icesat-2. ICESat-2 was launched in 2018, and can only be used to validate recent data. Details of methodology may be found in the related document, the Product Quality Assessment Report [D2].
Details of the product file format and contents are below. Details of methodology may be found in the related document, the Algorithm Theoretical Basis Document [D1].
1.2. Target requirements
Targets are set by two separate bodies. The Global Climate Observing System (GCOS) maintains definitions of ECVs and their requirements at https://gcos.wmo.int/en/essential-climate-variables/ice-sheets-ice-shelves/ecv-requirements
The Copernicus Climate Change Service (C3S) project itself provides key performance indicator targets.
Details of the CDR v4.0 performances against these targets may be found in the related document, the Product Quality Assessment Report [D2].
The requirements summarized for the SEC products, based on the combined GCOS and C3S performance indicator targets are shown in Table 2. These apply to both Antarctic and Greenland products. More information about the target requirements and the gaps within the current product characteristics can be found in the Target Requirement and Gap Analysis Document [D3].
Table 2: SEC products targets and performance indicators
Statistic | Target | Target source |
Stability at pixel-level | 0.1 m/y | GCOS |
Accuracy at basin-level | 0.1 m/y | GCOS |
Accuracy at pixel-level | 0.1 m/y | C3S project |
Surface coverage, aggregated over one year | 65% ERS1, ERS2, Envisat, Sentinel-3A/B | C3S project |
1.3. Data usage information
1.3.1. Product data format and content
The product is provided as a netCDF file containing stacked grids of the surface elevation change rate and associated uncertainty, and validity flags. The grids cover the Antarctic ice sheets, shelves, rises and islands at 25km x 25km resolution in a polar stereographic projection with centre longitude 0E and true scale latitude 71S, i.e. EPSG 3031 (https://epsg.io/3031). There is one grid per month, each cell containing the rate of surface elevation change derived from a 5-year period centred on that grid's timestamp. The change rate and its uncertainty are given in m/year. Missing data is indicated by a floating point NaN (not a number) value. Single-layer flag grids are provided for surface ice-cover type and slope range on the same projection as the data. The main variables are listed in Table 3 below.
Table 3: Antarctic surface elevation change main data variables.
Variable name | Variable description | Type |
x | Centre of grid cell on X axis, in m | 32-bit float |
y | Centre of grid cell on Y axis, in m | 32-bit float |
longitude | Longitude of grid cell centre, in degrees east | 32-bit float |
latitude | Latitude of grid cell centre, in degrees north | 32-bit float |
time | Central time of surface elevation change rate derivation, in hours since 1990.0 | 32-bit float |
sec | Surface elevation change rate, in m/year | 32-bit float |
sec_uncert | Uncertainty on surface elevation change rate, in m/yr | 32-bit float |
sec_ok | Validity flag for surface elevation change rate 0: no data in cell 1: data in cell | Byte |
surface_type | Flag for geographical surface type in cell 0: no ice (may be ocean) 1: ice cover > 95% of surface 2: ice shelf 3: ice rise or island within ice shelf | Byte |
high_slope | Flag for geographical slope class (ie low/medium/high) in cell 0: slope<= 2° 1: 2° < slope <= 5° 2: slope > 5° | Byte |
1.3.2. Product known limitations
Please note: the gridded data and its uncertainties are well-defined at pixel level. No smoothing has been applied across the geographic grid. If the pixels are to be combined to drainage basin level then the user should be sure to consider the varying terrain and ice dynamics within the basin - a simple mean value will not be representative.
1.3.3. Product nomenclature
The dataset filename format is
C3S_AntIS_RA_SEC_ggkm_versx_yyyy-mm-dd.nc, where:
- C3S is the overall project
- AntIS indicates the Antarctic ice sheet region
- RA indicates that the data source is radar altimetry
- SEC is the ECV addressed, ie surface elevation change
- gg is the grid resolution in km
- versx is the version number of the processing code
- yyyy-mm-dd is the creation date of the dataset
The latest file created should always be used, as the files are accumulative – each one contains all previous data as well as its monthly updates.
1.4. Structure of netCDF files
The header data for an example netCDF data file is given in Table 4.
Table 4: Sample of the structure of the provided NetCDF file for the Antarctic surface elevation change and exemplified by the October 2022 test dataset
netcdf C3S_AntIS_RA_SEC_25km_vers4_2022-10-13 {
dimensions:
x = 216 ;
y = 180 ;
t = 304 ;
bounds = 2 ;
variables:
float x(x) ;
x:long_name = "Cartesian x-coordinate - easting" ;
x:standard_name = "projection_x_coordinate" ;
x:short_name = "x" ;
x:units = "m" ;
x:axis = "X" ;
x:bnds = "grid_x_bounds" ;
float y(y) ;
y:long_name = "Cartesian x-coordinate - northing" ;
y:standard_name = "projection_y_coordinate" ;
y:short_name = "y" ;
y:units = "m" ;
y:axis = "Y" ;
y:bnds = "grid_y_bounds" ;
float longitude(y, x) ;
longitude:long_name = "Longitude" ;
longitude:standard_name = "longitude" ;
longitude:short_name = "lon" ;
longitude:units = "degrees_east" ;
longitude:bnds = "grid_lon_bounds" ;
float latitude(y, x) ;
latitude:long_name = "Latitude" ;
latitude:standard_name = "latitude" ;
latitude:short_name = "lat" ;
latitude:units = "degrees_north" ;
latitude:bnds = "grid_lat_bounds" ;
float time(t) ;
time:long_name = "SEC period central time" ;
time:standard_name = "time" ;
time:short_name = "time" ;
time:units = "hours since 1990-01-01T00:00:00Z" ;
time:calendar = "gregorian" ;
time:axis = "T" ;
time:bnds = "time_bounds" ;
float sec(y, x, t) ;
sec:long_name = "SEC" ;
sec:standard_name = "surface_elevation_change" ;
sec:short_name = "sec" ;
sec:units = "m/year" ;
sec:_FillValue = NaNf ;
sec:coordinates = "time x y" ;
sec:cell_methods = "area: mean time:linear_least_squares_fit" ;
float sec_uncert(y, x, t) ;
sec_uncert:long_name = "SEC uncertainty" ;
sec_uncert:standard_name = "surface_elevation_change_standard_error" ;
sec_uncert:short_name = "sec_uncertainty" ;
sec_uncert:units = "m/year" ;
sec_uncert:_FillValue = NaNf ;
sec_uncert:coordinates = "time x y" ;
sec_uncert:cell_methods = "area:mean area:uncertainty_sum time:linear_least_squares_fit time:uncertainty_sum" ;
byte sec_ok(y, x, t) ;
sec_ok:long_name = "SEC status flag" ;
sec_ok:standard_name = "surface_elevation_change status_flag" ;
sec_ok:short_name = "sec_status" ;
sec_ok:coordinates = "time x y" ;
sec_ok:valid_range = 0b, 1b ;
sec_ok:flag_values = 0b, 1b ;
sec_ok:flag_meanings = "no_data data_valid" ;
byte surface_type(y, x) ;
surface_type:long_name = "Surface type mask" ;
surface_type:standard_name = "surface_type status_flag" ;
surface_type:short_name = "surface_type" ;
surface_type:coordinates = "x y" ;
surface_type:valid_range = 0b, 3b ;
surface_type:flag_values = 0b, 1b, 2b, 3b ;
surface_type:flag_meanings = "no_ice ge_95_percent_ice ice_shelf ice_rise_or_island" ;
byte high_slope(y, x) ;
high_slope:long_name = "Surface slope flag" ;
high_slope:standard_name = "high_slope status_flag" ;
high_slope:short_name = "slope" ;
high_slope:coordinates = "x y" ;
high_slope:valid_range = 0b, 2b ;
high_slope:flag_values = 0b, 1b, 2b ;
high_slope:flag_meanings = "slope_le_2_degrees slope_gt_2_and_le_5_degrees slope_gt_5_degrees" ;
float grid_x_bounds(bounds, x) ;
grid_x_bounds:long_name = "Bounds of Cartesian x-coordinate - easting" ;
grid_x_bounds:standard_name = "projection_x_coordinate bounds" ;
grid_x_bounds:short_name = "x bounds" ;
grid_x_bounds:units = "m" ;
grid_x_bounds:axis = "X" ;
float grid_y_bounds(bounds, y) ;
grid_y_bounds:long_name = "Bounds of Cartesian y-coordinate - northing" ;
grid_y_bounds:standard_name = "projection_y_coordinate bounds" ;
grid_y_bounds:short_name = "y bounds" ;
grid_y_bounds:units = "m" ;
grid_y_bounds:axis = "Y" ;
float grid_lon_bounds(bounds, y, x) ;
grid_lon_bounds:long_name = "Longitude bounds" ;
grid_lon_bounds:standard_name = "longitude bounds" ;
grid_lon_bounds:short_name = "lon bounds" ;
grid_lon_bounds:units = "degrees_east" ;
grid_lon_bounds:grid_mapping = "grid_projection" ;
float grid_lat_bounds(bounds, y, x) ;
grid_lat_bounds:long_name = "Latitude bounds" ;
grid_lat_bounds:standard_name = "latitude bounds" ;
grid_lat_bounds:short_name = "lat bounds" ;
grid_lat_bounds:units = "degrees_north" ;
grid_lat_bounds:grid_mapping = "grid_projection" ;
float time_bounds(bounds, t) ;
time_bounds:long_name = "Time bounds" ;
time_bounds:standard_name = "time bounds" ;
time_bounds:short_name = "time bounds" ;
time_bounds:units = "hours since 1990-01-01T00:00:00Z" ;
time_bounds:calendar = "gregorian" ;
char grid_projection ;
grid_projection:ellipsoid = "WGS84" ;
grid_projection:false_easting = 0.f ;
grid_projection:false_northing = 0.f ;
grid_projection:grid_mapping_name = "polar_stereographic" ;
grid_projection:latitude_of_projection_origin = -90.f ;
grid_projection:standard_parallel = -71.f ;
grid_projection:straight_vertical_longitude_from_pole = 0.f ;
grid_projection:EPSG = "3413" ;
// global attributes:
:Conventions = "CF-1.7" ;
:title = "Surface Elevation Change Rate of the Antarctic Ice Sheet" ;
:references = "Main: Wingham, Shepherd, Muir and Marshall, Phil Trans R Soc A, doi:10.1098/rsta.2006.1792. Slope mask: Slater et al, The Cryosphere, 12,1551-1562, https://doi.org/10.5194/tc-12-1551-2018, 2018" ;
:source = "ESA Radar altimeters: ERS-1, ERS-2, Envisat, CryoSat-2, Sentinel-3A and Sentinel-3B " ;
:institution = "Copernicus Climate Change Service" ;
:contact = "copernicus-support@ecmwf.int" ;
:project = "C3S_312b_Lot4_ice_sheets_and_shelves" ;
:creation_date = "2022-10-13T:10:04:35Z" ;
:comment = "Data is geophysically corrected, instruments power corrected over as long a period as possible to max 5yrs (ERS1 phase C 1.5 yrs, ERS1 phase G 1yr, ERS2, Envisat, CryoSat-2 and Sentinel-3A 5 yrs and Sentinel-3B 3 yrs). SEC uses crossover method, cross-calibration by elevation regression. Time coverage 1994.83 to 2020.08 using data from 2.5 years further at each end of the range. Longitude 0 to 360 degrees, latitude -90 to -57.664 degrees. Grid_projection ESPG: 3031, ie PS 0E 71S WGS84, grid bottom left at -2.6e6m in x and -2.2e6m in y, grid cell width in x and y 25km" ;
:history = "Product version 4.0" ;
:summary = "Surface elevation change rate derived for Antarctica in 25km by 25km grid cells over a 5 year window moving at a monthly cadence." ;
:keywords = "EARTH SCIENCE CLIMATE INDICATORS CRYOSPHERIC INDICATORS GLACIAL MEASUREMENTS GLACIER ELEVATION/ICE SHEET ELEVATION, EARTH SCIENCE\tCRYOSPHERE GLACIERS/ICE SHEETS\tGLACIER ELEVATION/ICE SHEET ELEVATION" ;
:license = "C3S general license" ;
}
2. Surface elevation change, Greenland – WP2-FDDP-SEC-CDR-GrIS
2.1. Product description
The product contains surface elevation change rates and their associated uncertainties for the Greenland ice sheet and is provided on a regular grid at a monthly temporal resolution. The basis for the elevation change estimate for the older satellites (ERS-1, ERS-2 and Envisat) is a running 5-year mean, whereas for the ongoing satellite missions (Cryosat-2, Sentinel-3 A and B) the elevation change estimate is based on the monthly evaluation of a 3-year baseline. An example plot from one data grid is shown in Figure 2.
Figure 2: Example accumulated (in meters) surface elevation change map produced from product WP2-FDDP-SEC-CDR-GrIS from 1992 to 2009
The current version 4.0 of the CDR product builds on the legacy of its preceding versions:
CDRv1. The initial product release builds on the R&D efforts of the Greenland ice sheet Climate Change Initiative (CCI) project’s surface elevation measurements from ERS1, ERS2, Envisat and CryoSat-2.
CDRv2. Adds the use of observations from Sentinel-3A.
CDRv3. The time series have been reprocessed, with the upgraded baselines for Envisat and CryoSat-2 data and with the inclusion of data from Sentinel-3B.
CDRv4. The time series have been reprocessed, with the upgraded data filtering.
Similar to its predecessors, the current CDRv4 will be updated monthly as iCDRs, with a 2-month time lag between the acquisition of new measurements and their addition to the product. The product specifications are summarised in Table 5.
Table 5: Greenland SEC product specification summary
| Specification | Description |
|---|---|
| Sensors | ERS1 and ERS2 RA: https://earth.esa.int/eogateway/instruments/ra-ers/description Envisat RA-2: https://earth.esa.int/eogateway/instruments/ra2 Cryosat-2 SIRAL: https://earth.esa.int/eogateway/instruments/siral/description Sentinel-3A and Sentinel-3B SRAL: https://sentinels.copernicus.eu/web/sentinel/technical-guides/sentinel-3-altimetry/instrument/sral |
| Grid | 25km by 25km polar stereographic projection based on 45°W, 70°N on the WGS84 ellipsoid (EPSG: 3413) |
| Time range | 1992 to 2 months before present |
| Time intervals | 5-year window moving in monthly steps (3-year in the CryoSat-2 and Sentinel-3 era) |
| Validation frequency | Annual |
| Quality flagging | Flags are provided for steep terrain, missing data and the nearest distance to the original RA-altimeter measurement |
Validation is performed with respect to airborne measurements collected with the Airborne Topographic Mapper, a scanning laser altimeter, during Operation IceBridge campaigns (Studinger 2014), mission webpage at https://nsidc.org/data/icebridge. Validation is performed annually since Arctic campaigns take place once a year during the spring season (March-May). Additionally, independent data from the NASA ICESat-2 mission is used for validation after the cessation of Operation IceBridge campaigns in 2019 [D2].
Details of the product file format and contents are provided in the following section. Details of the methodology may be found in the related document, the Algorithm Theoretical Basis Document [D1].
2.2. Target requirements
The target requirements are generic for surface elevation change measurements. Hence, the same requirements as those listed for the Antarctic surface elevation change in Table 2 apply to Greenland too.
2.3. Data usage information
2.3.1. Product data format and content
The product is provided as a netCDF file containing stacked grids of the surface elevation change rate and associated uncertainty, and validity flags. Given in a north polar stereographic projection, with centre longitude 45W and latitude 70N, the grids cover the Greenland ice sheet at 25km x 25km. Solutions for the Greenland surface elevation change are given at a temporal resolution of one month, which combined with the 25 km grid gives a data array spanning the dimension of (65x123x364)1. The change rate and its uncertainty are given in m/year. Missing data is indicated by a floating-point NaN (not a number) value. Single-layer flag grids are provided for surface type and high slope. All single-layer flags are gridded using the same north-polar stereographic projection as the data. The main variables are listed in Table 6.
Table 6: Greenland surface elevation change main data variables.
Variable name | Variable description | Type |
x | Centre of grid cell on X axis, in m | 32-bit float |
y | Centre of grid cell on Y axis, in m | 32-bit float |
lon | Longitude of grid cell centre, in degrees east | 32-bit float |
lat | Latitude of grid cell centre, in degrees north | 32-bit float |
time | Central time of surface elevation change rate derivation, in hours since 1990.0 | 32-bit float |
dhdt | Surface elevation change rate, in m/year | 32-bit float |
dhdt_uncert | Uncertainty on surface elevation change rate, in m/yr | 32-bit float |
dhdt_ok | Validity flag for surface elevation change rate 0: no data in cell 1: data in cell | Byte |
surface_type | Flag for geographical surface type in cell 0: no ice (may be land or ocean) 1: ice cover > 95% of surface | Byte |
high_slope | Flag for geographical slope class (i.e. low/medium/high) in cell 0: slope<= 2° 1: 2° < slope <= 5° 2: slope > 5° | Byte |
dist | Distance to the nearest observational node, in m | int |
2.3.2. Product known limitations
Please note: The gridded data and its uncertainties are well-defined at the pixel level (25x25 km). If they are to be combined to drainage basin level the user should be sure to consider the varying terrain and ice dynamics within the basin - a simple mean value will not be representative. The performed kriging procedure has the capability of extrapolating data over undesired distances and the distance-flag should be consulted before any averaging of elevation change is performed.
2.3.3. Product nomenclature
The dataset filename format is
C3S_GrIS_RA_SEC_ggkm_versx_yyyy-mm-dd.nc, where:
- C3S is the overall project
- GrIS indicates the Greenland ice sheet region
- RA indicates that the data source is radar altimetry
- SEC is the ECV addressed, i.e. surface elevation change
- gg the grid size in km
- versx is the version number of the processing code
- yyyy-mm-dd is the creation date of the dataset
The latest file created should always be used, as the files are cumulative – each one contains all previous data as well as its monthly updates.
2.4. Structure of NetCDF files
The header data for an example netCDF data file is given in Table 7.
Table 7: Example of the NetCDF file structure for the Greenland Ice Sheet Surface elevation change based on the October 2023 version 4.0 dataset.
netcdf file:/Users/ssim/space/nfs/g7/PROJ/C3S/SEC/v4/SECicdr/C3S_GrIS_RA_SEC_25km_Vers4_2022-10-19.nc {
dimensions:
x = 65;
t = 364;
y = 123;
variables:
float x(x=65);
:long_name = "Cartesian x-coordinate - easting";
:standard_name = "projection_x_coordinate";
:units = "m";
float y(y=123);
:long_name = "Cartesian y-coordinate - northing";
:standard_name = "projection_y_coordinate";
:units = "m";
float time(t=364);
:long_name = "SEC period central time";
:standard_name = "time";
:units = "hours since 1990-01-01T00:00:00Z";
float start_time(t=364);
:standard_name = "time";
:long_name = "SEC period start time";
:units = "hours since 1990-01-01T00:00:00Z";
float end_time(t=364);
:standard_name = "time";
:long_name = "SEC period end time";
:units = "hours since 1990-01-01T00:00:00Z";
char grid_projection;
:ellipsoid = "WGS84";
:false_easting = 0.0; // double
:false_northing = 0.0; // double
:grid_mapping_name = "polar_stereographic";
:latitude_of_projection_origin = 90.0; // double
:standard_parallel = 70.0; // double
:straight_vertical_longitude_from_pole = -45.0; // double
:EPSG = "3413";
float lat(y=123, x=65);
:_FillValue = 9999.0f; // float
:units = "degrees_north";
:grid_mapping = "grid_projection";
:long_name = "Latitude";
:_ChunkSizes = 123U, 65U; // uint
float lon(y=123, x=65);
:_FillValue = 9999.0f; // float
:units = "degrees_east";
:grid_mapping = "grid_projection";
:long_name = "longitude";
:_ChunkSizes = 123U, 65U; // uint
float dh(y=123, x=65, t=364);
:long_name = "Elevation change";
:grid_mapping = "grid_projection";
:units = "m";
:_ChunkSizes = 62U, 33U, 182U; // uint
float dh_uncert(y=123, x=65, t=364);
:long_name = "Elevation change uncertainty";
:grid_mapping = "grid_projection";
:units = "m";
:_ChunkSizes = 62U, 33U, 182U; // uint
float dhdt(y=123, x=65, t=364);
:long_name = "Rate of elevation change";
:grid_mapping = "grid_projection";
:units = "m/year";
:_ChunkSizes = 62U, 33U, 182U; // uint
float dhdt_uncert(y=123, x=65, t=364);
:long_name = "Rate of elevation change uncertainty";
:units = "m/year";
:grid_mapping = "grid_projection";
:_ChunkSizes = 62U, 33U, 182U; // uint
float dhdt_stabil(y=123, x=65, t=364);
:grid_mapping = "grid_projection";
:units = "m/year";
:long_name = "Stability of rate of elevation change fit";
:_ChunkSizes = 62U, 33U, 182U; // uint
byte dhdt_ok(y=123, x=65, t=364);
:grid_mapping = "grid_projection";
:flag_values = 0B, 1B; // byte
:flag_meanings = "no_data data_valid";
:long_name = "SEC valid flags";
:_ChunkSizes = 123U, 65U, 364U; // uint
float dist(y=123, x=65, t=364);
:long_name = "Distance to observational node";
:grid_mapping = "grid_projection";
:unit = "m";
:_ChunkSizes = 62U, 33U, 182U; // uint
byte land_mask(y=123, x=65);
:ref = "ESA Glacier CCI Greenland ice cover";
:flag_meanings = "0_LandOcean 1_IceCover";
:long_name = "Land cover";
:grid_mapping = "grid_projection";
:flag_values = 0B, 1B; // byte
:_ChunkSizes = 123U, 65U; // uint
byte high_slope(y=123, x=65);
:flag_meanings = "0Slope_leq_2degrees 1Slope_geq2leq5degrees 2Slope_geq_5degrees";
:grid_mapping = "grid_projection";
:ref = "Slope of the GIMP Greenland DEM";
:long_name = "Slope flag";
:flag_values = 0B, 1B, 2B; // byte
:_ChunkSizes = 123U, 65U; // uint
float area(y=123, x=65);
:long_name = "Grid_area";
:grid_mapping = "grid_projection";
:units = "m^2";
:_ChunkSizes = 123U, 65U; // uint
// global attributes:
:Title = "Surface Elevation change of the Greenland ice sheet from Radar altimetry";
:institution = "Copernicus Climate Change Service, DTU Space - Div. of Geodynamics";
:reference = "Simonsen and Sørensen (2017), Sørensen et al. (2018)";
:contact = "copernicus-support@ecmwf.int";
:file_creation_date = "2022-10-19 17:40:43.048938";
:project = "C3S_312b_Lot4_ice_sheets_and_shelves";
:region = "Greenland";
:missions_used = "ESA Radar altimeters: ERS-1,ERS-2, Envisat, CryoSat-2 and Sentinel-3";
:power_corrections = "ERS-1, ERS-2 and Envisat 5-years, CryoSat-2 3-years";
:grid_projection = "EPSG:3413";
:grid_minx = -739301.6214372054; // double
:grid_miny = -3478140.668199717; // double
:grid_nx = 65L; // long
:grid_ny = 123L; // long
:grid_cell_width_x = "25000 m";
:grid_cell_width_y = "25000.0m";
:Latitude_min = 57.76737214534745; // double
:Latitude_max = 86.04798347855436; // double
:Longitude_min = -104.92422366476225; // double
:Longitude_max = 18.552684627240275; // double
:model_type = "ERS-1, ERS-2 and Envisat combined repeat-track and plan-fitting, with the introduction of CryoSat-2 only plane fit is used";
:cross_cal_method = "Elevation regression, and weighted mean";
:time_coverage_start = "1992-01-01 00:00:00";
:time_coverage_end = "2022-04-01 00:00:00";
:Tracking_id = "94b58830-2488-45b9-8eb6-8f563fbadc09";
:Internal_ref = "C3S_GrIS_RA_SEC_25km_Vers4_2022-10-19.nc";
:netCDF_version = "NETCDF4";
:product_version = "v4";
:Conventions = "CF-1.7";
:keywords = "EARTH SCIENCE CRYOSPHERE GLACIERS/ICE SHEETS/GLACIER ELEVATION/ICE SHEET ELEVATION";
:license = "C3S general license";
:summary = "Surface elevation change rate derived for Greenland in 25km by 25km grid cells over a 5/3 year window moving monthly cadence.";
}
3. Data access information
3.1. All products
Data will be made available through the Copernicus Climate Data Store (CDS), which is the sole data distributor. Registration (free) is required to access the CDS and its toolbox software suite. The CDS is a web-based service, with its homepage at https://cds.climate.copernicus.eu/cdsapp#!/home
Data can be downloaded from the website and used under the License to Use Copernicus Products (included on the download page). The data is provided in NetCDF (Network Common Data Form) files which are a user-friendly way for scientists and researchers to store and share complex scientific data, like climate models and Earth observations, in digital containers. These files make it easier to analyse and understand things like weather patterns and ocean behaviour, facilitating collaboration and advancements in various fields of study. Data may also be viewed online https://cds.climate.copernicus.eu/cdsapp#!/dataset/satellite-ice-sheet-elevation-change?tab=app.
All requests for information or further data should be channelled through the CDS Knowledge Base at https://confluence.ecmwf.int//display/CKB/
References
Studinger, M. (2014). IceBridge ATM L4 Surface Elevation Rate of Change, Version 299 1, Antarctica subset. N. S. a. I. D. C. D. A. A. Center. Boulder, Colorado, USA. DOI: 10.5067/BCW6CI3TXOCY
This document has been produced in the context of the Copernicus Climate Change Service (C3S).
The activities leading to these results have been contracted by the European Centre for Medium-Range Weather Forecasts, operator of C3S on behalf of the European Union (Contribution agreement signed on 22/07/2021). All information in this document is provided "as is" and no guarantee or warranty is given that the information is fit for any particular purpose.
The users thereof use the information at their sole risk and liability. For the avoidance of all doubt , the European Commission and the European Centre for Medium - Range Weather Forecasts have no liability in respect of this document, which is merely representing the author's view.
