DOI: 10.5281/zenodo.13707842
title: ECCO Iter22 Global Ocean State Estimate - 1 January 2004 to 30 April 2005

description: Time series of global ocean temperature, salinity, and sound speed derived from the “Estimating the Circulation and Climate of the Ocean" (ECCO) program Iter22 state estimates.  The sound speed fields were computed for simulation of acoustic propagation over basin scales or longer in a realistic oceanic environment.  These estimates  were computed in 2010 by the JPL-MIT-SIO ECCO program.                                                     Original link: http://ecco2.jpl.nasa.gov/data9/cube/iter22/lat_lon/quart_80S_80N/THETA/ , now defunct.

The solution is mesoscale permitting.  The solution was obtained on a cube sphere grid between 80S and 80N with 18-km horizontal grid spacing and 50 vertical levels (Menemenlis et al., 2005, NASA supercomputer improves prospects for ocean      climate research, Eos Trans., AGU 86, 89, 95–96.).  State estimates were averaged over a 3-day interval. File 003 is averaged over 2004/1/1 -- 2004/1/3.  Three-day-mean temperature and salinity profiles from the iter22 solution were provided on 1/4 degree grid for the period 1 January 2004 to 30 April 2005. There are 162 snapshots at 3-day intervals. 

Depths were decimated to the standard 33 depths of the World Ocean Atlas to 5500 m.   YearDay 1 is 1 January 1992.  The number of the filename indicates the yearday in 2004.  In situ temperature was computed from model potential temperature.  Sound speed was computed using the Del Grosso sound speed equation.  Original model profiles descended only to the model sea floor.  Temperature, salinity and sound speed were filled in on a uniform grid using nearest neighbor to 5500 m depth.  Values on a regular grid make life easier.  Product documented in Dushaw and Menemenlis, 2014, Antipodal acoustic thermometry: 1960, 2004, Deep Sea Research Part I: Oceanographic Research Papers, 86, 1–20, https://doi.org/10.1016/j.dsr.824 2013.12.008.

Each snapshot is stored as a netcdf 4 file.  Latitude, Longitude, Depth, and YearDay variables given separately in sspgrid.nc .       N.B.: Values in the files are stored as 32-bit or 16-bit integers to save disk space:

Sound Speed:  saved as "round( (c-1000)*1000 )", so to get actual c: c=1000. + double(c)/1000. Sound speed is stored to 3 decimal places as a 32-bit integer.

Temperature: saved as   "round( (T-10)*1000 )", so to get actual T: T=10. + double(T)/1000. Temperature is stored to 3 decimal places as a 16-bit integer.  Note that abyssal temperature can sometimes be negative.

Salinity: saved as   "round( (S-10)*1000 )", so to get actual S: S=10. + double(S)/1000. Salinity is stored to 3 decimal places as a 16-bit integer.

Data directory also has two matlab routines: get_section.m and dist.m.  get_section.m shows how to load the files, compute the physical variable from the stored value, and compute a section of ssp, T, or S.   dist.m is a utility for computing geodesics; it relies on R. Pawlowitz's m_map package which can be downloaded freely from his University of Vancouver web page.

$ md5sum *tgz 53ca3621f422b89c599c92fbab71d2fc  S_ecco_iter22.tgz    (2.99 GB)a9e9109b6dae7355bf2fa0926d436d9a  ssp_ecco_iter22.tgz  (6.09 GB)0cb8d1c2cdee4c7377353dff722ece34  T_ecco_iter22.tgz    (4.33 GB)
description: Global values of ocean temperature, salinity, and sound speed derived from state estimates from the MIT-JPL-SIO ECCO program in 2010.  The state estimate name is "Iter22" with global values at 1/4 degree resolution and 33 depths in the vertical.  Data are stored as netcdf 4 files.  The original purpose of the sound speed estimates was to simulate long-range acoustic propagation in a realistic oceanic environment.   The state estimates are, of course, constrained by all available data, but are also "mesoscale permitting".  Files are 3-day averages estimating the actual oceanic state from the period 1 January 2004 to 30 April 2005.