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Description

This dataset provides geometric parameters for the SASSIE ECCO Version 1 Release 1 (V1R1) ocean and sea-ice state estimate. Parameters include areas and lengths of grid cell sides; horizontal and vertical coordinates of grid cell centers and corners; grid rotation angles; and global domain geometry including bathymetry and land/ocean masks. ECCO (Estimating the Circulation and Climate of the Ocean) is a 4D ocean circulation model combining observations with a general circulation model (GCM) to estimate the complete time-evolving state of the global ocean. In this project, it was run over the Arctic polar region in support of the Salinity and Stratification at the Sea Ice Edge (SASSIE) field experiment - a NASA experiment focused on salinity anomalies in the upper ocean generated by melting sea ice. The SASSIE ECCO simulation was produced by downscaling the global ECCO state estimate from 1/3 to 1/12 degree grid cells, where the global solution provided initial and boundary conditions and atmospheric forcing. The output fields for this dataset cover the period 2014-01-15T12:00:00 to 2021-02-07T12:00:00 and are consolidated onto a single curvilinear grid face focusing on the Arctic domain, using the 5 faces of the lat-lon-cap 1080 (llc1080) native grid from the original simulation. Ocean density and pressure are provided at 90 depth levels from 0.5 meters to 6760 meters. Daily files are available in netCDF-4.
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This dataset is one of 22 produced by SASSIE ECCO - the full list can be found in the user guide. To cite all 22 datasets with a single DOI, please cite the user guide (citation details and DOI can be found within the user guide).

Version Description

Version 1, Release 1

Product Summary

Platforms
MITgcm
Location
ARCTIC
Coordinate System
GEODETIC
Granule Spatial Representation
GEODETIC
Temporal Extent
2014-01-15 to 2021-02-08
Temporal Resolution
1 Day
Vertical Extent
Maximum Depth: 6760<br>Minimum Depth: 0.5
Data Partner
Physical Oceanography Distributed Active Archive Center, Jet Propulsion Laboratory, NASA (NASA/JPL/PODAAC)
Concept ID
C3706337498-POCLOUD
Data State
COMPLETE
Number of Files/Granules
1
Processing Level
4
Science Keywords
Ocean Circulation

Citation

Citation is critically important for dataset documentation and discovery. This dataset is openly shared, without restriction, in accordance with the EOSDIS Data Use and Citation Guidance.

Copy Citation

Marie Zahn, M. W. (2026). SASSIE ECCO Geometry Parameters - llc1080 Grid (Version 1 Release 1) [Data set]. NASA Physical Oceanography Distributed Active Archive Center. https://doi.org/10.5067/SEL1S-GEO11 Date Accessed: 2026-01-29

Documents

Variables

Variables are a set of physical properties whose values determine the characteristics or behavior of something. For example, temperature and pressure are variables of the atmosphere. Parameters and variables can be used interchangeably. Variable level attributes provide individual information for each variable.

The Name in this table is the variable name. Fill value indicates missing or undefined data points in a variable. Valid range is the range of values the variable can store. Scale factor is used to increase or decrease the size of an object and can be used to correct for distortion. For questions on a specific variable, please use the Earthdata Forum.

Name Description Units Data Type Fill Value Valid Range Scale Factor
CS CS and SN are required to calculate the geographic (meridional, zonal) components of vectors on the curvilinear model grid. Note: for vector R with components R_x and R_y: R_{east} = CS R_x - SN R_y. R_{north} = SN R_x + CS R_y 1 float 9.96921E+36 -0.99999958276749 to 0.99999976158142 1
Depth Model sea surface height of 0m corresponds to an ocean surface at rest relative to the geoid. Depth corresponds to seafloor depth below geoid. Note: the MITgcm used by ECCO implements &#039;partial cells&#039; so the actual model seafloor depth may differ from the seafloor depth provided by the input bathymetry file. m float 9.96921E+36 0 to 7000.0400390625 1
drC The first element corresponds to the distance between the depth of the center of the uppermost model grid cell and the surface. m float 9.96921E+36 0.5 to 458.98498535156 1
drF Grid cell thickness. m float 9.96921E+36 1 to 479.73999023438 1
dxC Alternatively, the length of &#039;north&#039; side of vorticity grid cells. Note: &#039;north&#039; does not correspond to geographic orientation but is used for convenience to describe the computational grid. See MITgcm documentation for details. m float 9.96921E+36 473.40902709961 to 5744.0659179688 1
dxG Alternatively, the length of &#039;south&#039; side of tracer grid cell. Note: &#039;south&#039;, &#039;southwest&#039;, and &#039;southeast&#039; do not correspond to geographic orientation but are used for convenience to describe the computational grid. See MITgcm documentation for details. m float 9.96921E+36 385.54302978516 to 5746.6752929688 1
dyC Alternatively, the length of &#039;east&#039; side of vorticity grid cells. Note: &#039;east&#039; does not correspond to geographic orientation but is used for convenience to describe the computational grid. See MITgcm documentation for details. m float 9.96921E+36 473.40902709961 to 6117.3735351562 1
dyG Alternatively, the length of &#039;west&#039; side of tracer grid cell. Note: &#039;west, &#039;southwest&#039;, and &#039;northwest&#039; do not correspond to geographic orientation but are used for convenience to describe the computational grid. See MITgcm documentation for details. m float 9.96921E+36 466.45309448242 to 6114.2348632812 1
hFacC Tracer grid cells may be fractionally closed in the vertical. The open vertical fraction is hFacC. The model allows for partially-filled cells to represent topographic variations more smoothly (hFacC &lt; 1). Completely closed (dry) tracer grid cells have hFacC = 0. 1 float 9.96921E+36 0 to 1 1
hFacS The &#039;south&#039; face of tracer grid cells may be fractionally closed in the vertical. The open vertical fraction is hFacS. The model allows for partially-filled cells for smoother representation of seafloor topography. Tracer grid cells adjacent in the &#039;y&#039; direction that are partially closed in the vertical have hFacS &lt; 1. Note: The term &#039;south&#039; does not correspond to geographic orientation but is used for convenience to describe the computational grid. See MITgcm documentation for details. 1 float 9.96921E+36 0 to 1 1
hFacW The &#039;west&#039; face of tracer grid cells may be fractionally closed in the vertical. The open vertical fraction is hFacW. The model allows for partially-filled cells for smoother representation of seafloor topography. Tracer grid cells adjacent in the &#039;x&#039; direction that are partially closed in the vertical have hFacW &lt; 1. Note: The term &#039;west&#039; does not correspond to geographic orientation but is used for convenience to describe the computational grid. See MITgcm documentation for details. 1 float 9.96921E+36 0 to 1 1
i In the Arakawa C-grid system, tracer (e.g., THETA) and &#039;v&#039; variables (e.g., VVEL) have the same x coordinate on the model grid. N/A int N/A N/A 1
i_g In the Arakawa C-grid system, &#039;u&#039; (e.g., UVEL) and &#039;g&#039; variables (e.g., XG) have the same x coordinate on the model grid. N/A int N/A N/A 1
j In the Arakawa C-grid system, tracer (e.g., THETA) and &#039;u&#039; variables (e.g., UVEL) have the same y coordinate on the model grid. N/A int N/A N/A 1
j_g In the Arakawa C-grid system, &#039;v&#039; (e.g., VVEL) and &#039;g&#039; variables (e.g., XG) have the same y coordinate. N/A int N/A N/A 1
k grid index in z for tracer variables N/A int N/A N/A 1
k_l First index corresponds to the top face of the uppermost tracer grid cell. The use of &#039;l&#039; in the variable name follows the MITgcm convention for naming the top face of ocean tracer grid cells. N/A int N/A N/A 1
k_p1 Includes top of uppermost model tracer cell (k_p1=0) and bottom of lowermost tracer cell (k_p1=91). N/A int N/A N/A 1
k_u First index corresponds to the bottom face of the uppermost tracer grid cell. The use of &#039;u&#039; in the variable name follows the MITgcm convention for naming the bottom face of ocean tracer grid cells. N/A int N/A N/A 1
maskC True for tracer grid cells with nonzero open vertical fraction (hFacC &gt; 0), otherwise False. N/A byte N/A N/A 1
maskS True for grid cells with nonzero open vertical fraction along their &#039;south&#039; face (hFacS &gt; 0), otherwise False. N/A byte N/A N/A 1
maskW True for grid cells with nonzero open vertical fraction along their &#039;west&#039; face (hFacW &gt; 0), otherwise False. N/A byte N/A N/A 1
mask_basin One for wet tracer grid cells (maskC = True) that are connected to the ocean. Zero for tracer grid cells with no open vertical fraction (maskC = False) or wet grid cells that are isolated from the ocean. This mask fills small, enclosed basins where water is surrounded by land and not connected to the open ocean. N/A int N/A 0 to 1 1
PHrefC PHrefC = p_ref (k) / rhoConst = rhoConst g z(k) / rhoConst = g z(k), where p_ref(k) is reference hydrostatic ocean pressure at center of tracer grid cell k, rhoConst is reference density (1027.5 kg m-3), g is acceleration due to gravity (9.81 m s-2), and z(k) is depth at center of tracer grid cell k. Units: p:[kg m-1 s-2], rhoConst:[kg m-3], g:[m s-2], z_m(t):[m]. Note: does not include atmospheric pressure loading. Quantity referred to in some contexts as hydrostatic pressure potential. PHIHYDcR is anomaly of PHrefC. m2 s-2 float 9.96921E+36 4.9050002098083 to 66317.265625 1
PHrefF PHrefF = p_ref (k_l) / rhoConst = rhoConst g z(k_l) / rhoConst = g z(k_l), where p_ref(k_l) is reference hydrostatic ocean pressure at lower interface of tracer grid cell k, rhoConst is reference density (1027.5 kg m-3), g is acceleration due to gravity (9.81 m s-2), and z(k) is depth at center of tracer grid cell k. Units: p:[kg m-1 s-2], rhoConst:[kg m-3], g:[m s-2], z_m(t):[m]. m2 s-2 float 9.96921E+36 0 to 68670.390625 1
rAc area of tracer grid cell m2 float 9.96921E+36 265756.21875 to 35154560 1
rAs Model &#039;u&#039; grid cells are staggered in space between adjacent tracer grid cells in the &#039;y&#039; direction. &#039;u&#039; grid cell (i,j) is situated at the &#039;south&#039; edge of tracer grid cell (i, j). Note: &#039;south&#039; does not correspond to geographic orientation but is used for convenience to describe the computational grid. See MITgcm documentation for details. m2 float 9.96921E+36 216632.984375 to 35154560 1
rAw Model &#039;v&#039; grid cells are staggered in space between adjacent tracer grid cells in the &#039;x&#039; direction. &#039;v&#039; grid cell (i,j) is situated at the &#039;west&#039; edge of tracer grid cell (i, j). Note: &#039;west&#039; does not correspond to geographic orientation but is used for convenience to describe the computational grid. See MITgcm documentation for details. m2 float 9.96921E+36 242413.921875 to 35120572 1
rAz Vorticity cells are staggered in space relative to tracer cells, nominally situated on tracer cell corners. Vorticity cell (i,j) is located at the &#039;southwest&#039; corner of tracer grid cell (i, j). Note: &#039;southwest&#039; does not correspond to geographic orientation but is used for convenience to describe the computational grid. See MITgcm documentation for details. m2 float 9.96921E+36 130281.390625 to 35188572 1
SN CS and SN are required to calculate the geographic (meridional, zonal) components of vectors on the curvilinear model grid. Note: for vector R with components R_x and R_y in local grid directions x and y, the geographical eastward component R_{east} = CS R_x - SN R_y. The geographical northward component R_{north} = SN R_x + CS R_y. 1 float 9.96921E+36 -0.99999994039536 to 1 1
XC nonuniform grid spacing degrees_east float N/A -179.9994354248 to 179.99996948242 1
XC_bnds Bounds array follows CF conventions. XC_bnds[i,j,0] = &#039;southwest&#039; corner (j-1, i-1), XC_bnds[i,j,1] = &#039;southeast&#039; corner (j-1, i+1), XC_bnds[i,j,2] = &#039;northeast&#039; corner (j+1, i+1), XC_bnds[i,j,3] = &#039;northwest&#039; corner (j+1, i-1). Note: &#039;southwest&#039;, &#039;southeast&#039;, northwest&#039;, and &#039;northeast&#039; do not correspond to geographic orientation but are used for convenience to describe the computational grid. See MITgcm documentation for details. N/A float N/A N/A 1
XG Nonuniform grid spacing. Note: &#039;southwest&#039; does not correspond to geographic orientation but is used for convenience to describe the computational grid. See MITgcm documentation for details. degrees_east float N/A -179.99998474121 to 180 1
XU The u point is at midpoint between the &#039;southwest&#039; and &#039;northwest&#039; corners of the tracer grid cell. Grid spacing is nonuniform. Note: &#039;west&#039; refers to the computational grid orientation and does not necessarily correspond to geographic west. See MITgcm documentation and Arakawa C grid notation for details. degrees_east float N/A -179.99995422363 to 179.99995422363 1
XV The v point is at midpoint between the &#039;southwest&#039; and &#039;southeast&#039; corners of the tracer grid cell. Grid spacing is nonuniform. Note: &#039;south&#039; refers to the computational grid orientation and does not necessarily correspond to geographic south. See MITgcm documentation and Arakawa C grid notation for details. degrees_east float N/A -179.99990844727 to 180 1
YC nonuniform grid spacing degrees_north float N/A 48.678619384766 to 89.978286743164 1
YC_bnds Bounds array follows CF conventions. YC_bnds[i,j,0] = &#039;southwest&#039; corner (j-1, i-1), YC_bnds[i,j,1] = &#039;southeast&#039; corner (j-1, i+1), YC_bnds[i,j,2] = &#039;northeast&#039; corner (j+1, i+1), YC_bnds[i,j,3] = &#039;northwest&#039; corner (j+1, i-1). Note: &#039;southwest&#039;, &#039;southeast&#039;, northwest&#039;, and &#039;northeast&#039; do not correspond to geographic orientation but are used for convenience to describe the computational grid. See MITgcm documentation for details. N/A float N/A N/A 1
YG Nonuniform grid spacing. Note: &#039;southwest&#039; does not correspond to geographic orientation but is used for convenience to describe the computational grid. See MITgcm documentation for details. degrees_north float N/A 48.652767181396 to 90 1
YU The u point is at midpoint between the &#039;southwest&#039; and &#039;northwest&#039; corners of the tracer grid cell. Grid spacing is nonuniform. Note: &#039;west&#039; refers to the computational grid orientation and does not necessarily correspond to geographic west. See MITgcm documentation and Arakawa C grid notation for details. degrees_north float N/A 48.652774810791 to 89.984642028809 1
YV The v point is at midpoint between the &#039;southwest&#039; and &#039;southeast&#039; corners of the tracer grid cell. Grid spacing is nonuniform. Note: &#039;south&#039; refers to the computational grid orientation and does not necessarily correspond to geographic south. See MITgcm documentation and Arakawa C grid notation for details. degrees_north float N/A 48.678611755371 to 89.984642028809 1
Z Non-uniform vertical spacing. The associated &#039;Z_bnds&#039; coordinate provides the depths of top and bottom faces of the tracer grid cell, with one pair of depths for each vertical level. m float N/A -6760.169921875 to -0.5 1
Zl First element is 0m, the depth of the top face of the uppermost tracer grid cell (i.e., the ocean surface). Last element is the depth of the top face of the deepest grid cell. The use of &#039;l&#039; in the variable name follows the MITgcm convention for naming the top face of ocean tracer grid cells. m float N/A -6520.2998046875 0 1
Zp1 Contains one element more than the number of vertical layers. First element is 0m, the depth of the top face of the uppermost grid cell. Last element is the depth of the bottom face of the deepest grid cell. m float N/A -7000.0400390625 0 1
Zu First element is -1m, the depth of the bottom face of the uppermost tracer grid cell. Last element is the depth of the bottom face of the deepest grid cell. The use of &#039;u&#039; in the variable name follows the MITgcm convention for naming the bottom face of ocean tracer grid cells. m float N/A -7000.0400390625 to -1 1
Z_bnds Provides the depths of the top and bottom faces of the tracer grid cell, with one pair of depths for each vertical level. N/A float N/A N/A 1
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