Archive of Spotlight Feature Articles

Building a Sustained
Ocean Observing System for Climate

by Michael Johnson

Central to describing, understanding, and predicting the earth's climate system is observation. The mission of the observational element of NOAA's climate services is to build and sustain the global climate observing system that is needed to satisfy the long term requirements of the operational forecast centers, international research programs, and the major scientific assessments. NOAA's climate observation program is built on the recognition that national and international partnerships are essential to success. A global observing system by definition crosses international boundaries and the potential exists for both benefits and burdens to be shared by many nations.

The climate observation program supports both ocean and atmospheric components, but the ocean has received the most attention to date because climate research has left ocean observing system legacies that must be transitioned to an operational framework. Today NOAA laboratories, university partners, and volunteer observing ships operate about 60% of the fledgling in situ ocean observing system for climate. This international effort is about 25% of what will be needed over the long term.

Now NOAA is embarking on a comprehensive implementation plan to work with national and international partners to complete the needed global system. It will take ten years. The plan is based on the concept of extending the building blocks that have been put in place by the research programs, and on the international plan drafted by over 300 scientists from 26 nations that met in Saint Raphael, France, October 1999, at the OCEANOBS 99 Conference.

Initial Ocean Observing System Milestones
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Recognizing that the climate observing system will evolve as knowledge increases, NOAA has defined an initial set of objectives and milestones to guide a phased implementation over the next ten years. The system is a composite of complementary networks, both in-situ and space-based, all internationally coordinated. Each network brings its unique strengths and limitations; together they build the whole. The initial milestones provide realistic targets while at the same time providing flexibility for evolution of the design as technology improves and the patterns of climate variability become clearer.

Milestones for the in situ networks:

Deploy an array of 1250 drifting buoys for sea surface temperature, pressure, and current measurement, by 2004.
Deploy an array of 3000 Argo floats for upper ocean temperature and salinity profiling, by 2004.
Deploy 106 tropical moorings for measurements of the ocean, atmosphere, and ocean/atmosphere exchanges, by 2007.
Establish 86 tide gauges for altimeter drift calibration and documenting long term trends in sea level change, by 2006.
One hundred, fourteen coastal moorings operated traditionally for weather forecasting will be enhanced for climate observation, by 2006.
Establish 16 ocean reference station moorings to provide a sparse network of high accuracy calibration points and fixed sites for documenting long term trends in the ocean, by 2006.
Occupy 41 volunteer observing ship (VOS) lines for high accuracy upper ocean and surface meteorological observations, by 2007.

Plus two satellites:

NOAA and NASA will transition from research (NASA) to operational status (NOAA) the U.S. partnership in continuous altimeter and scatterometer flights for global sea level and surface wind determinations, by 2010.

Plus system-wide infrastructure:

Research ship operations for high accuracy ocean climate observation, ocean carbon inventories, and deployment of the autonomous platforms (the moored and drifting arrays) will be systemized by 2010.
Data and assimilation systems will bring all these networks together in delivering routine ocean analyses through the international Global Ocean Data Assimilation Experiment (GODAE) by 2007.

When completed, this composite system will deliver continuous, long term, climate quality, global data sets and a suite of routine ocean analyses:

For the global ocean, four-times-daily analyses of sea surface pressure, sea surface wind, and marine weather and sea state conditions.
For the global tropics, daily analyses of precipitation, sea surface temperature, and air-sea fluxes.
For the global ocean, weekly analyses of upper ocean temperature and salinity, sea surface temperature, and sea level.
For the global ocean, an ocean carbon inventory once every ten years, and seasonal (four-times-yearly) analyses of the variability of ocean-atmosphere carbon exchange.
At fixed climate reference stations, documented long term trends in sea level change and ocean/atmosphere variability.

These observing system deliverables comprise the essential raw materials from the ocean that will be needed by the climate forecasters, researchers, and the assessments in order for them to deliver the climate services that are of economic value to the nation and the world.

Global Ocean Observing System for Climate and Marine Services
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