Field Measurements for Passive Environmental Remote Sensing: Instrumentation, Intensive Campaigns, and Satellite Applications - Chapter 5: Oceanographic buoys: Providing ocean data to assess the accuracy of variables derived from satellite measurements

The collection of independent in situ field measurements of ocean and atmospheric parameters is a crucial element of passive environmental satellite calibration and validation (hereafter cal/val). Despite multigenerational efforts by scientists, engineers, and the crew aboard research and commercial vessels (see Chapter 11), it remains a daunting challenge to maintain an ocean observing system capable of assessing the accuracy of variables derived from satellite measurements on a global scale. Oceanographic buoys, defined here as floating, drifting, or anchored ocean observing platforms, have long been used to collect data in the ocean either during relatively short-term process studies that support science-based inquiries, or as part of sustained programs that contribute near-real-time data for operational and scientific use. The form and function of oceanographic buoys vary tremendously and includes anchored surface and subsurface moorings, and quasi-Lagrangian buoys that follow fluid motion in two or three-dimensions. Some of these buoys may spend their lifetime at the sea surface (e.g., surface drifting buoys); some transit the ocean following a fixed depth, pressure, or density surface (e.g., isobaric floats); some move three dimensionally through the water column collecting measurements as they ascend or descend (e.g., Argo profiling floats), some are affixed to the seafloor by an anchor, collecting measurements just above the seafloor, from the seafloor to an intermediate depth, or from the seafloor to the sea surface (e.g., moored buoys with subsurface or surface flotation).