Temperature profiles from expendable bathythermograph (XBT) casts from the USCGC ACUSHNET in the Gulf of Mexico in support of the Integrated Global Ocean Services System (IGOSS) from 13 August 1975 to 15 August 1975 (NODC Accession 7500779)

XBT data were collected from the USCGC ACUSHNET in support of the Integrated Global Ocean Services System (IGOSS). Data were collected by the US Coast Guard from 13 August 1975 to 15 August 1975. Data were processed by NODC to the NODC standard Universal Bathythermograph Output (UBT) format. Full format description is available from NODC at www.nodc.noaa.gov/General/NODC-Archive/bt.html.

The UBT file format is used for temperature-depth profile data obtained using expendable bathythermograph (XBT) instruments. 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.

XBT（expendable Bathythermograph，投弃式海温剖面仪）数据由美国海岸警卫队“阿库什尼特”号（USCGC ACUSHNET）采集，用于支撑全球海洋综合服务系统（Integrated Global Ocean Services System, IGOSS）。该数据的采集时段为1975年8月13日至1975年8月15日，由美国海岸警卫队完成现场数据采集。美国国家海洋数据中心（National Oceanographic Data Center, NODC）将原始数据处理为NODC标准通用海水温度剖面输出（Universal Bathythermograph Output, UBT）格式。完整格式说明可从NODC官方网站获取，网址为www.nodc.noaa.gov/General/NODC-Archive/bt.html。

UBT文件格式用于存储通过投弃式海温剖面仪采集得到的温度-深度剖面数据。标准型XBT可获取约450米或760米深度的剖面数据；若搭配专用仪器，测量深度可达1830米。每条观测记录均包含航次信息、观测位置、日期及时间信息。数据记录由多组温度-深度值对构成。与以5米均匀间隔记录温度值的机械式海水温度剖面仪（Mechanical Bathythermograph, MBT）数据文件不同，XBT数据文件中的温度值对应非均匀分布的深度点，这些点为将温度曲线记录至可接受精度所需的最少拐点数量。不过在数据输出环节，用户可选择直接获取拐点处的温度值，或通过插值运算得到均匀深度间隔下的温度值。