Tropical Ocean Global Atmosphere

Project Description
In order to better understand the tropical ocean/atmosphere system and
its effect on the climate at higher latitudes, the Tropical Ocean and
Global Atmosphere (TOGA) Program was initiated in 1985 by the World
Meteorological Organization (WMO), with contributions from nations
including the USA, UK, USSR, Japan, Australia, India and Chile. TOGA
was a major component of the WMO's World Climate Research Program
(WCRP) and was effective in bringing together the international
scientific research community to work on problems of global
significance. Scientific oversight was provided by the TOGA
Scientific Steering Group who reports to the Joint Scientific
Committee of WCRP. International coordination was organized through
the International TOGA Project Office in Geneva and the 18-member
Intergovernmental TOGA Board.

The U.S. contribution to TOGA involved the National Oceanic
Atmospheric Administration (NOAA), National Science Foundation (NSF),
and the National Aeronautics and Space Administration (NASA). NOAA
involvement includes the Climate Analysis Center (CAC), NOAA
Environmental Research Laboratories (Pacific Marine Environmental
Laboratory (PMEL), Atlantic Oceanographic and Meteorological
Laboratory (AOML), Geophysical Fluid Dynamics Laboratory (GFDL), and
the Climate Monitoring and Diagnostics Laboratory (CMDL), and the
National Oceanographic Service (NOS). NSF support was funded
through its Ocean and Atmospheric Sciences Divisions and through NCAR.
NASA's effort was funded to NASA centers and academic principal
investigators while the Office of Naval Research (ONR) supports a
number of university scientists.

TOGA is a 10-year international program that began January 1, 1985 and
continued through 1994.

The major elements of the TOGA Praogram Plan are modeling, empirical
studies, process studies and long-term observations. Three types of
models are being used: (1) oceanographic models, in which the wind
stress and heat flux at the air-sea interface are prescribed and the
time-dependent response of the upper layers of the tropical ocean is
simulated; (2) atmospheric models, in which the global circulation is
simulated given various prescriptions of the tropical SST field; and
(3) coupled atmosphere-ocean models, which are integrated forward in
time from a prescribed set of initial conditions. Empirical studies
are focusing on interannual and intraseasonal variability along with
statistical analyses of lead-lag relationships that may have relevance
to seasonal climate prediction. Long-term observations include
interfacial measurements, and atmospheric and oceanographic
observations.

Science Objective:
-To gain a description of the tropical oceans and the global atmosphere as a
time-dependent system, in order to determine the extent to which this system
is predictable on time scales of months to years, and to understand the
mechanisms and processes underlying that predictability.
-To study the feasibility of modeling the coupled ocean-atmosphere system for
the purpose of predicting its variations on time scales of months to years.
-To provide the scientific background for designing an observing and data
transmission system for operational prediction if this capability is
demonstrated by coupled ocean-atmosphere models.


Data Used and Produced:
Long-term monitoring is among the more focused of the program elements
of TOGA. It is a prerequisite for numerical simulation and long-term
prediction of the coupled climate system, and it supports process and
empirical studies. Interfacial measurements such as wind stress, sea
surface temperature (SST) and surface energy fluxes are most central
to the ocean-atmosphere coupling and are attaining the highest
priority. The major sources of surface wind data over the tropical
oceans are moored buoys, ships of opportunity and island stations.
The moored buoys transmit wind, air temperature, SST and subsurface
temperature via the ARGOS/TIROS-N system. Wind observations from
ships and island stations are transmitted via the Global
Telecommunication System (GTS). The CAC has been producing monthly
mean SST analyses with about 2 degree spatial resolution, based upon a
blend of in situ (ship and buoy) data and Advanced Very High
Resolution Radiometer (AVHRR) satellite data, while also monitoring
net energy flux monthly mean fields generated by one of the
operational numerical weather prediction models at the National
Meteorological Center (NMC).

Observations of the global atmosphere in suapport of TOGA relied
heavily on the World Weather Watch/Global Telecommunications System
(WWW/GTS). The observing network consists of two polar-orbiting
satellites and the full array of geostationary satellites, ships of
opportunity, buoys, and surface and upper-air stations. The Global
Precipitation Center at CAC has been supportive in producing
preliminary estimates of tropical convective precipitation from
1986-1988 based on satellite imagery from the U.S., Japan and the
European Space Agency (ESA) geostationary satellites. Ships of
opportunity and approximately 50 drifting buoys are being used to
measure sea level pressure, air temperature and SST over data-sparse
regions of the equatorial and extratropical South Pacific. The
National Center for Atmospheric Research (NCAR) and ERL have
contributed some upper-air systems and Doppler profilers to the
surface and upper-air network.

The ocean observing system consisted of tidal gauges, satellite data,
moored (ATLAS) and drifting (Langrangian) buoys and and ships of
opportunity. The island tide gauge network along with altimetric
range data obtained from military satellites provided sea level data.
Expendable Bathythermograph System (XBT) lines from ships provided
soundings to analyze the thermal structure and the heat content. Ships
also carried out conductivity, temperature and depth (CTD) surveys in
the upper 1000m of the ocean. Moored buoys, instrumented with current
meters and thermistor chains also provided subsurface thermal
structure and current data. Circulation was measured utilizing
equatorial moorings and from a field of over 130 mixed-layer
Langrangian drifters.

The following sites on the World Wide Web can provide further information
as well as data access:
TOGA COARE Data Information System
http://www.ncdc.noaa.gov/coare/
TOGA-TAO Realtime Data Access:
http://www.pmel.noaa.gov/tao/

References:
National Research Council, 'TOGA, A Review of Progress and Future
Opportunities', National Academy Press 1990.

World Meteorological Organization, 'WMO/IOC Inter-governmental TOGA Board
Report of the Third Session, Geneva, 9-12 January 1990', WMO/TD No. 357.

World Meteorological Organization, 'JSC/CCCO TOGA Scientific Steering
Group Report of the Eighth Session, Hamburg, 18-22 September 1989',
WMO/TD No. 338.