Frequently asked questions bout ocean observations
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Figure legend: ARGI is global array of 3,000 free-drifting profiling floats that measures the temperature and salinity of the upper 2000 m of the ocean. 3.4) What is a satellite-tracked surface drifter? A satellite-tracked drifter is an autonomous surface float that is deployed from both research and commercial vessels and then allowed to drift freely across the oceans. The drifter package is designed to be deployed from underway ships. Drifters can also be deployed from aircraft when packaged in specifically designed boxes with parachutes. A drifter consists of a spherical surface buoy tethered to a subsurface semi-rigid drogue, (see anchor). The surface float ranges from 30.5 to 40 cm in diameter and contains the batteries that power the drifter’s instruments and transmission packages. All drifters are equipped with a sea surface temperature sensor. Some drifters include additional instruments including barometric pressure, wind speed and direction, salinity and/or ocean color sensors. They also have a submergence sensor or a tether strain sensor to verify the presence of the drogue. The drogue is centered at 15 meters beneath the surface to measure mixed layer currents in the upper ocean. The outer surface of the drogue is made of nylon cloth. Throughout the drogue, rigid rings with spokes support the unit’s cylindrical shape. The drogue is a “holey-sock”: each drogue section contains two opposing holes, which are rotated 90 degrees from one section to the next. These holes act like the dimples of a golf ball by disrupting the formation of organized lee vortices. The drifter sensors (e.g., SST, drogue attachment) average data over a window (typically 90 seconds) and transmit the data to a satellite at 401.65 MHz. The position of a drifter is inferred from the Doppler shift of its transmission as seen by the receiving satellite. The accuracy of a drifter position varies with the number of satellite used to track a particular float. Three classes of accuracy are available: class 3 (less than 150 m error), class 2 (150-350 m error), and class 1 (350-1000 m error). Each drifter transmitter is assigned unique ID number. This ID can be used to access drifter data. Surface drifter data are used to characterize the near surface currents of the global ocean. The characterization is needed to increase understanding of what factors drive changes in ocean circulation, an important component of the earth’s climate system. They also provide the temperature data needed to calibrate SST observations from space. Coupled with satellite altimetry data they can be used to decompose surface currents into those driven by surface wind forcing and those by density differences, additional information needed to understand ocean variability. For more information on the surface drifter activities of the Physical Oceanography Division of NOAA’s Atlantic Oceanographic and Meteorological Laboratory go to: http://www.aoml.noaa.gov/phod/dac/gdp_drifter.html 
Figure legend: Deployed surface drifter. 
Figure legend: Two long trajectories, one in the southern and the other in the northern hemisphere. 3.5) What is a TSG (ThermoSalinoGraph)? TSGs are instruments mounted close to the water intake (used for engine cooling) of research and cargo ships. The TSG obtains water continuously from the ship’s intake and the TSG sensors measure the salinity and temperature at the depth of the intake along the track of the ship. Stored data can be obtained when the ship returns to port or if transmission equipment is available can be obtained via satellite. 
Data from TSG are used to characterize the surface temperature and salinity structure of the ocean. Once a satellite that can measure surface salinity is launched, TSGs will provide calibration data for the remote sensors. For more information on the TSG activities of the Physical Oceanography Division of NOAA’s Atlantic Oceanographic and Meteorological Laboratory go to: Directory: phod -> pub -> lusic lusic -> Physical Oceanography Division cy-2010 Publications pub -> North Atlantic Gyre Circulation Variability Associated with the Atlantic Multidecadal Oscillation phod -> Chunzai Wang phod -> March 2018 Cruise Plan – ax18 Download 16.64 Mb. Share with your friends:
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