Temperature profiles from expendable bathythermograph (XBT) casts from the USCGC EVERGREEN in the North Atlantic Ocean in support of the Integrated Global Ocean Services System (IGOSS) project from 05 April 1974 to 03 May 1974 (NODC Accession 7400785)

XBT data were collected from the USCGC EVERGREEN in support of the Integrated Global Ocean Services System (IGOSS) project. Data were collected by the US Coast Guard (USCG) from 05 April 1974 to 03 May 1974. 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.

本数据集的XBT（投弃式温深仪，Expendable Bathythermograph）数据采集自美国海岸警卫队“常青”号巡逻舰，服务于全球海洋综合服务系统（Integrated Global Ocean Services System, IGOSS）项目。数据采集时段为1974年4月5日至1974年5月3日，由美国海岸警卫队（United States Coast Guard, USCG）完成采集。数据已由美国国家海洋数据中心（National Oceanographic Data Center, NODC）处理为NODC标准通用温深仪输出（Universal Bathythermograph Output, UBT）格式。完整格式说明可通过NODC官方网站www.nodc.noaa.gov/General/NODC-Archive/bt.html获取。

UBT文件格式用于存储通过投弃式温深仪获取的温度-深度剖面数据。标准型投弃式温深仪可获取约450米或760米深度的剖面数据；若搭载专用特殊仪器，最大测量深度可达1830米。每份观测数据均配套记录航次信息、观测位置、日期与时间。数据记录由多组温度-深度数值对组成。与机械温深仪（Mechanical Bathythermograph, MBT）数据文件不同——后者的温度值按均匀5米间隔进行记录——XBT数据文件中的温度值对应非均匀深度。这些非均匀深度点为将温度曲线记录至可接受精度所需的最少采样点，即“拐点”。不过在数据输出环节，用户可选择直接提取拐点处的温度值，或通过插值运算得到均匀深度间隔下的温度数据。