CryoSat-SMOS Merged Sea Ice Thickness

Version	Date	Comments
v201	10.01.2019	Official ESA release

Product Description Overview

Parameter	Sea ice thickness
Spatial covergae	N: 90°, S:16.6°, E:180°, W:-180°
Spatial Resolution	25 km x 25 km
Temporal Coverage:	November 2010 to present
Temporal Resolution	7 days
Data Format(s)	NetCDF
Platforms	CryoSat-2, SMOS
Version	v201

File naming convention

NetCDF files are named using the following convention:

<convention-prefix>_<regional code>- <institution>,<platform(s)>,<grid>_<time>_<mode>_<product version>_<file version>.nc

convention-prefix	World Meteorological Organization: W
regional code	European: XX
institution	European Space Agency: ESA
processing level/parameter	level 4 sea ice thickness: l4sit
Platform(s)	Satellites: SMOS, CS2
grid	25 km EASE2 grid, Northern Hemisphere: NH_25KM_EASE2
time	time span: yyyymmdd - yyyymmdd
mode	reprocessing: r, operational: o
product version	version 2.0.0: v200
file version	Version 1: 01

Example NetCDF naming for operationally processed data:

W_XX-ESA,SMOS_CS2,NH_25KM_EASE2_20180326_20180401_o_v201_01_l4sit.nc

Example NetCDF naming for reprocessed data:

W_XX-ESA,SMOS_CS2,NH_25KM_EASE2_20180326_20180401_r_v201_01_l4sit.nc

File Format

The weekly grids are given in standardized binary data format (Network common data form: NetCDF v4). Global attributes are given in Table 2. The variables are given as grid arrays, see, therefore Table 3. NetCDF files are formatted according to CF conventions: CF-1.6 ACDD-1.3. We use a scaling factor of 10^-3 and a fillvalue = -2147483647.

Table 2: Global attributes from an example NetCDF file, covering the week from March 26 to April 01, 2018.

Attribute	Value
title	Sea Ice Thickness derived from merging CryoSat-2 and SMOS ice thickness
description	Weekly Arctic sea-ice thickness derived from CryoSat-2 and SMOS using an optimal interpolation scheme
summary	Weekly Arctic sea-ice thickness derived from CryoSat-2 and SMOS using an optimal interpolation scheme
keywords	Cryosphere > Sea Ice > Sea Ice Thickness
product_version	201
processing_mode	r
time_of_creation	Mon Oct 22 17:27:55 2018
history	Mon Oct 22 17:27:55 2018 creation
Conventions	CF-1.6 ACDD-1.3
spatial_resolution	25.0 km grid spacing
geospatial_lat_min	16.623929977416992
geospatial_lat_max	90.0
geospatial_lon_min	-180.0
geospatial_lon_max	180.0
geospatial_vertical_min	0.0
geospatial_vertical_max	0.0
time_coverage_start	2018-03-26T00:00:00Z
time_coverage_end	2018-04-01T00:00:00Z
time_coverage_duration	P7D
time_coverage_resolution	P7D
platform	CryoSat-2, SMOS
project	CS2SMOS PDS: SMOS & CryoSat-2 Sea Ice Data Product Processing and Dissemination Service
institution	Alfred-Wegener-Institut Helmholtz Zentrum für Polar und Meeresforschung (AWI), http://www.awi.de
creator_name	Alfred-Wegener-Institut Helmholtz Zentrum für Polar und Meeresforschung (AWI), http://www.awi.de
creator_type	institution
creator_url	https://spaces.awi.de/confluence/x/DwVmEQ
publisher_email	robert.ricker@awi.de
references	Ricker, R., Hendricks, S., Kaleschke, L., Tian-Kunze, X., King, J., and Haas, C.: A weekly Arctic sea-ice thickness data record from merged CryoSat-2 and SMOS satellite data, The Cryosphere, 11, 1607-1623, https://doi.org/10.5194/tc-11-1607-2017, 2017.
_CoordSysBuilder	ucar.nc2.dataset.conv.CF1Convention

Table 3: NetCDF file content. Note, that we use a scaling factor of 10^-3 and a fillvalue = -2147483647.

Variable	Description	Unit	Type	Dimension
Lambert_Azimuthal_Grid	proj4_string: +proj=laea +lon_0=0 +datum=WGS84 +ellps=WGS84 +lat_0=90.0	-	int	-
time_bnds	start and end time of the weekly retrieval	seconds since 1978-01-01 00:00:00	double	2
analysis_ice_thickness	CS2SMOS weekly merged sea ice thickness	m	int	1,432,432
background_ice_thickness	background field, interpolation using CS2 and SMOS sea ice thickness data	m	int	1,432,432
weighted_mean_ice_thickness	weighted mean of weekly CS2 and SMOS ice thickness retrievals	m	int	1,432,432
innovation	difference between background and analysis ice thickness	m	int	1,432,432
ice_conc	sea ice concentration (OSI-401)	%	int	1,432,432
ice_type	sea ice type (OSI-403)	-	int	1,432,432
correlation_length_scale	correlation length scale of background ice thickness	m	int	1,432,432
analysis_thickness_unc	uncertainty of the merged sea ice thickness	m	int	1,432,432
smos_ice_thickness	weekly averaged SMOS ice thickness	m	int	1,432,432
cs2_ice_thickness	weekly averaged CryoSat-2 ice thickness	m	int	1,432,432
time	reference time of product (middle of the week)	seconds since 1978-01-01 00:00:00	double	1
xc	x coordinate of projection (eastings)	km	double	432
yc	y coordinate of projection (northings)	km	double	432
lon	longitude coordinate	degrees_north	float	432,432
lat	latitude coordinate	degrees_east	float	432,432

Grid

All grids are projected onto the 25 km EASE2 Grid, which is based on a polar aspect spherical Lambert azimuthal equal-area projection (Brodzik et al., 2012). The grid dimension is 5400 km x 5400 km, equal to a 432 x 432 grid. The grid is centered on the geographic Pole, meaning that the Pole is located at the intersection of center cells (Figure 1).