How We Observe the Ocean
Surface Drifting Buoys
The Global Drifter Program (GDP) is comprised of an array of about 1250 drifting buoys that provide operational, near-real time surface velocity, sea surface temperature (SST) and sea level pressure observations for numerical weather forecasting, research, and in-situ calibration/verification of satellite observations. The array provides the largest area coverage of all components of the global ocean observing system for surface temperature and currents. The GDP is managed in close cooperation between the NOAA Atlantic Oceanographic and Meteorological Laboratory (AOML) in Miami, Florida, and the branch of the NOAA Cooperative Institute for Marine Ecosystems and Climate (CIMEC) located at the Scripps Institution of Oceanography in La Jolla, California.
- Global Drifter Array
- Drifter Links
Global sea surface temperature analyses are derived from satellite retrievals, but the satellite measurements must be continuously calibrated using surface in situ measurements. To that end, drifting buoys measure temperature 20-30 cm beneath the sea surface. The design for the global surface drifting buoy array (GCOS-92) calls for 1,250 buoys to be maintained world-wide, spaced approximately 500 km apart in order to adequately tune satellite measurements. The drifter array also provides the primary source of global ocean surface circulation measurements, which are necessary to validate climate and ocean forecast models. Some drifters are equipped with barometers to provide critical, near real-time observations of atmospheric pressure for numerical weather prediction, as well as to document global-scale trends in climate variability. Additional drifters are equipped with salinity sensors to calibrate sea surface salinity observations from satellites. The drifters report hourly via satellite communications. Specially equipped “hurricane drifters” are now routinely air-dropped in the path of hurricanes approaching the U.S. coast in order to improve hurricane intensity and landfall predictions.
The global drifting buoy array reached its initial design goal of 1,250 data buoys in sustained service in 2005. The next challenge is to equip all buoys with barometers, and to install salinity sensors on a subset of 300 buoys, particularly in the sub-polar regions for analysis of freshwater input from melting ice sheets and changes in thermohaline circulation.
The NOAA global drifter program is managed in close cooperation with about a dozen other countries that contribute to this subsystem under the framework of the JCOMM Data Buoy Cooperation Panel. NOAA/AOML arranges and conducts drifter deployments, processes the data, maintains files which describe each drifter, and hosts the GDP website. CIMEC oversees manufacture and acquisition of drifters from industrial partners, technology upgrades, development of new sensors, and creation of enhanced data sets.
Drifter data are made available in near-real time on the Global Telecommunications System for weather forecasting efforts. Delayed mode data are made available after quality control and interpolation, which takes about three months, at the Global Drifter Program Data Assembly Center at the NOAA Atlantic Oceanographic and Meteorological Laboratory, and, six months later, are archived and distributed by the Canadian Integrated Science and Data Management program.
Global Drifter Program
Drifter Global Data Assembly Centers