The Global Drifter Center at AOML has responsibility for the logistics of drifter deployment and quality control of the resulting data. In July 1995, data were logged from more than 750 buoys. An XBT is a small instrument that is dropped into the ocean from a ship. During its descent at a constant rate, an XBT measures the temperature of the seawater through which it descends, and sends these measurements back to the ship through two fine wires that connect the ship to the instrument. XBTs generally have a depth limit of 750 meters, but some reach depths of 1800 meters.
Many ships relay summaries of the vertical profiles of temperature back to the shore by satellite.
Meteorological centers throughout the world receive data from both the XBTs and the buoys via a global communications network, and use it to prepare the analyses that are essential for forecasts of weather and climate. The complete vertical temperature profiles are sent to data collection centers after the ships reach port. The Upper Ocean Thermal Center at AOML has responsibility for quality control of an average of 2,000 XBTs per month. Observations from buoys and XBTs have other uses as well. AOML scientists have used the data to verify the models being developed for climatic forecasts, and to study climatically important upper ocean processes.