UOT Data Collection
NOAA, other national groups and the international community have established several mechanisms for the collection of UOT data which are described below. An important consideration when designing these mechanisms for data acquisition is the sampling srategy necessary for particular scientific or operational needs.
To date, the primary source of UOT data has been the XBT Volunteer Observing Ship (VOS) program using Shipboard Environmental data Acquisition Systems (SEAS) for data collection and transmission. SEAS was developed by NOAA to provide accurate meteorological and oceanographic data in real time from ships at sea through the use of satellite data transmission techniques. The system transmits data through either the GOES or INMARSAT satellites to NOAA. Currently, SEAS has the capability to transmit surface weather, XBT, CTD and ADCP data.
Recently, two other observing systems have been deployed to provide UOT data. First, in the tropical Pacific, an array of moored buoys, the TOGA-TAO array, measures surface atmospheric and subsurface oceanographic variables for TOGA (Fig. 3). Although initially designed to observe surface wind fields, the TAO array provides continuous observations of UOT structure.
Second, Davis et al. (1992) describe a subsurface float that was originally developed to provide trajectories at preselected depths of the water column. The float is timed to return to the surface at desired intervals to transmit its position data through a satellite link to a land station. This ALACE float has since been modified to provide both temperature and salinity profiles obtained during its return to the surface.
In all three observing systems, the data are transmitted via
satellite from the collection point to a land station where they
typically undergo some quality control. The data are then
retransmitted and captured by users such as CMP for various purposes.
Data not transmitted in real-time are collected by data centers such as
NODC, collated and then forwarded, at different intervals, to quality
control centers for review. After editing, the data are returned to
the data centers for storage and dissemination to other users.