Array for Real-Time Geostrophic Oceanography (ARGO)

A broad-scale global array of temperature/salinity profiling floats,
known as Argo, is planned as a major component of the ocean observing
system, with deployment scheduled to begin in 2000. Conceptually,
Argo builds on the existing upper-ocean thermal networks, extending
their spatial and temporal coverage, depth range and accuracy, and
enhancing them through addition of salinity and velocity measurements.
The name Argo is chosen to emphasize the strong complementary
relationship of the global float array with the Jason altimeter
mission. For the first time, the physical state of the upper ocean
will be systematically measured and assimilated in near real-time.

Objectives of Argo fall into several categories. Argo will provide a
quantitative description of the evolving state of the upper ocean and
the patterns of ocean climate variability, including heat and
freshwater storage and transport. The data will enhance the value of
the Jason altimeter through measurement of subsurface vertical
structure (T(z), S(z)) and reference velocity, with sufficient
coverage and resolution for interpretation of altimetric sea surface
height variability. Argo data will be used for initialization of
ocean and coupled forecast models, data assimilation and dynamical
model testing. A primary focus of Argo is seasonal to decadal climate
variability and predictability, but a wide range of applications for
high-quality global ocean analyses is anticipated.

The initial design of the Argo network is based on experience from the
present observing system, on newly gained knowledge of variability
from the TOPEX/Poseidon altimeter, and on estimated requirements for
climate and high-resolution ocean models. Argo will provide 100,000
T/S profiles and reference velocity measurements per year from about
3000 floats distributed over the global oceans at 3-degree spacing.
Floats will cycle to 2000 m depth every 10 days, with a 4-5 year
lifetime for individual instruments. All Argo data will be publicly
available in near real-time via the GTS, and in scientifically
quality-controlled form with a few months delay. Global coverage
should be achieved during the Global Ocean Data Assimilation
Experiment, which together with CLIVAR and GCOS/GOOS, provide the
major scientific and operational impetus for Argo. The design
emphasizes the need to integrate Argo within the overall framework of
the global ocean observing system.

International planning for Argo, including sampling and technical
issues, is coordinated by the Argo Science Team. Nations presently
having Argo plans that include float procurement or production include
Australia, Canada, France, Japan, U.K., and U.S.A., plus a European
Union proposal. Combined deployments from these nations are expected
to exceed 700 floats per year by 2002. Broad participation in Argo by
many nations is anticipated and encouraged either through float
procurement, logistical support for float deployment, or through
analysis and assimilation of Argo data.

The Argo data (in NetCDF format) are freely available from two Argo Global Data
Assembly Centres (GDAC): the Coriolis and US-GODAE GDAC servers. The Coriolis
GDAC is updated daily in real-time data from Data Assembly Centers (DAC): US
AOML, Canadian MEDS, Japanese JMA, EU Coriolis. The US- GODAE GDAC is
currently operational, serving daily data (updated every hour) from the
following national DACs: Australian (CSIRO), Canadian (MEDS), Indian (INCOIS),
Korean ( KMA), Japanese (JMA), UK (BODC), and US (AOML).