The following group of four related files contains temperature profile data (temperature versus depth) from the mechanical bathythermograph (MBT) and its successor instrument, the expendable bathythermograph (XBT). Although the NODC still receives some MBT data (in digital form) from foreign sources, most new data are from XBTs. XBT data are received in delayed mode as analog strip charts (that must be digitized), as digital data already derived from analog strip charts, and, increasingly, as digital data recorded directly on cassette tapes by newer XBT systems. NODC also receives BT data in near-real-time as telecommunicated (radio message) observations collected in support of the Integrated Global Ocean Services System (IGOSS). Because they vary in quality, the way in which they are reported to the NODC, and the depths at which they are recorded, the data are maintained in separate files. The data are all recorded in the same format, however, and may be merged if desired.

This file format is used for temperature-depth profile data obtained using the mechanical bathythermograph (MBT) instrument. The maximum depth of MBT observations is approximately 285 m. Therefore, MBT data are useful only in studying the thermal structure of the upper layers of the ocean. Cruise information, date, position, and time are reported for each observation. The data record comprises pairs of temperature-depth values. Temperature data in this file are recorded at uniform 5 m depth intervals.

(Note: The mechanical bathythermograph instrument is now obsolete, having been superseded by the faster, easier-to-operate expendable bathythermograph.)

This file format is used for temperature-depth profile data obtained using expendable bathythermograph (XBT) instrument. Standard XBTs can obtain profiles at depths of about 450 or 760 m. With special instruments, measurements can be obtained to 1830 m. Cruise information, position, date, and time are reported for each observation. The data record comprises pairs of temperature-depth values. Unlike the MBT data file, in which temperature values are recorded at uniform 5m intervals, the XBT Data File contains temperature values at non-uniform depths. These depths are at a minimum number of points ("inflection points") required to record the temperature curve to an acceptable degree of accuracy. On output, however, the user may request temperature values either at inflection points or interpolated to uniform depth increments.

This file format is used for temperature-depth data obtained from mechanical (MBT) and expendable (XBT) bathythermograph instruments. Data in this file were sent to NODC at depths selected by the originator - usually at standard horizons or some fixed interval. The MBT file holds data reported at a 5-meter depth interval, and depths in the XBT file are chosen at significant inflection points of the temperature-depth profile. SBT data can be selected from specific geographic regions or from specified cruises.

This file format is used for telecommunicated bathythermograph (principally XBT) data transmitted by ships at sea over the Global Telecommunications System in the Integrated Global Ocean Services System (IGOSS) BATHY format. These data are accumulated and transmitted to NODC from two U.S. operational centers: the NOAA National Meteorological Center (NMC) and the U.S. Navy Fleet Numerical Oceanography Center (FNOC). Like XBT data, IBT data temperature values are recorded at inflection point depths. The BATHY radio message allows for a limited number of depth-temperature pairs to be reported, however. Therefore, compared to delayed-mode XBT data, IBT data present a coarser representation of ocean temperature profiles.

One variable-length record (maximum 2,540 characters).

*DEPTH-TEMPERATURE PAIRS (8 CHARACTERS) REPEATED AS MANY TIMES AS INDICATED BY 'COUNT' FIELD UP TO MAXIMUM OF 305 PAIRS (2440 CHARACTERS); MAXIMUM RECORD LENGTH, THEREFORE EQUALS 2440 + 100 (HEADER INFORMATION) = 2540 CHARACTERS.