Argo Products at the Asia-Pacific Data-Research Center
Konstantin Lebedev, Sharon DeCarlo, Peter Hacker, Nikolai Maximenko, James Potemra, Yingshuo Shen
University of Hawaii – International Pacific Research Center, Honolulu, Hawaii, USA
http://apdrc.soest.hawaii.edu/projects/argo/
Email: KLEBEDEV@soest.hawaii.edu
Argo product development at the Asia-Pacific Data-Research Center (APDRC) is providing the research community with near-real time, globally
unified, user friendly, research quality datasets derived from Argo float profiles and trajectories with the concurrent use of satellite and in situ
data. Global Argo products include binned, interpolated and derived quantities. For example, surface and deep velocities from float trajectories;
profile data interpolated onto standard depth levels and isopycnals; mixed layer, isothermal layer and barrier layer depths; statistics,
climatologies, and monthly and annual averages; and maps of data coverage. All these are available as binary and ascii files as well as pregenerated plots.
Ensemble mean potential temperature, salinity, isopycnal depth, and
Ensemble mean potential temperature, salinity, potential density, and
Montgomery Potential on 26.9 isopycnal as observed by Argo
absolute dynamic depth at 700 m depth as observed by Argo floats
floats and averaged over 1x1 degree bins
and averaged over 1x1 degree bins
The Variational Interpolation (VI) technique is used to spatially
interpolate Argo data. The principle of the VI technique is to minimize
the misfit between the interpolated fields defined on a regular grid
and the irregularly distributed data, so the optimal solution passes as
close to the data as possible.
Cost function
F = (Agrid – Adata)2 +
C1 (Agrid - Adata)2+
C2  (Agrid)2 ds
+
(only for dynamic height)
C3  (Agrid – Aclimate)2 ds
“A” is an Argo variable to be gridded (T, S, dynamic height, etc.)
January 2010 mean Temperature at 200 m depth as observed by Argo
floats and averaged over 3x3 degree bins versus interpolated using VI
Over the past decade, Argo floats have provided an unprecedented
number of temperature and salinity profiles of the global ocean and
revolutionized the distribution of ocean data within the scientific
community. The original design of the Argo mission specified nominal 3
x 3 degree spacing, providing the most extensive and uniformly
distributed dataset of oceanographic measurements ever. The array
was 100% complete by November 2007. Today there is a global array of
more than 3,000 free-drifting floats measuring the temperature and
salinity of the upper 2000 m of the ocean with a 10-day sampling
interval.
Argo is an international collaboration that collects high-quality
temperature and salinity profiles from the upper 2000m of the ice-free
global ocean and currents from intermediate depths. The data come
from battery-powered autonomous floats that spend most of their life
drifting at depth where they are stabilized by being neutrally buoyant at
the "parking depth" pressure by having a density equal to the ambient
pressure and a compressibility that is less than that of sea water. At
present there are three models of profiling float used extensively in
Argo. All work in a similar fashion but differ somewhat in their design
characteristics. At typically 10-day intervals, the floats pump fluid into
an external bladder and rise to the surface over about 6 hours while
measuring temperature and salinity. Satellites determine the position of
the floats when they surface, and receive the data transmitted by the
floats. The bladder then deflates and the float returns to its original
density and sinks to drift until the cycle is repeated. Floats are designed
to make about 150 such cycles.
January 2010 mean Salinity at 200 m depth as observed by Argo floats
and averaged over 3x3 degree bins versus interpolated using VI
Annual mean Salinity at 10 m depth as observed by Argo floats and
averaged over 3x3 degree bins from 2001 to 2009 and ensemble mean
Argo floats Salinity averaged over 1x1 degree bins (lower right panel )
Aviso altimetry referred to Miximenko and Niiler (2005) MDOT was used to calculate Absolute Dynamic Depth and Montgomery Potential
Ensemble mean velocity magnitude at the surface (top) and 1000 m
(bottom) derived from Argo floats displacements and averaged over
1x1 degree bins
Winter (JFM) mean mixed layer depth (top) and barrier layer thickness
(bottom) as derived from Argo profiles and averaged over 1x1 degree
bins
Absolute Dynamic Topography
A major synthesis product under development is an estimate of the
four-dimensional Absolute Dynamic Topography, from which the
geostrophic velocity field can be estimated. Absolute dynamic
topography is computed using data from Argo profiles, float
trajectories, drifters, satellite wind and Aviso altimetry.
January 2010 map of Absolute Dynamic Topography at 1000 m