Airborne-deployed ocean sensors in the Southern Ocean, 2016-2018, Level 2 data

Extracted Level 2 data include three data types: 1)    Position data are included in .GPX files organized by campaign where “ICP8” refers to the 2016-2017 ICECAP2 field season and “ICP9” refers to the 2017-2018 field season. We recommend opening these files in QGIS or on similar platform. Metadata for each sonobuoy deployment include the unique identifier for each profile as well as the date, time, and aircraft longitude, latitude, elevation, and speed (in East, North, Up coordinates) at the time of deployment. Season identifier, flight number, and unique profile identifier are also displayed. In QGIS, for example, clicking on the drop locations using the “Identify Features” tool is a convenient way of investigating the metadata.2)    Profile data are released as Exportable Data Files (EDF), an ASCII format with a metadata header followed by the profile data.3)    Profile data are also released as Hierarchical Data Format (HDF) files using a .h5 extension. This format is provided so users can take advantage of numerous and freely available Python and MATLAB resources simplifying importing and investigating the profiles.Project 4346 demonstrated the use of Airborne eXpendable Bathy-Thermograph (AXBT) and Airborne eXpendable Conductivity, Temperature, Depth (AXCTD) sensors from a BT-67 Basler aircraft in East Antarctica. The primary objective was to use AXBT and AXCTD sensors to infer seafloor depth where no previous measurements had been made by ship, often by deploying sensors into narrow gaps in sea ice. Inferring a snapshot of the ocean state by detecting major thermoclines was a secondary objective.Although several sensors were purchased with external funds, the efforts to develop operational and subsequent data analysis approaches were unfunded as this was an add-on, target of opportunity. The effort is best described as a prototype demonstration project to test whether the seafloor depth could be inferred beneath narrow sea ice leads from a rapidly flying aircraft. All but eight AXBT sensors were donated to the University of Texas Institute for Geophysics (UTIG); AXCTDs were purchased by the Antarctic Gateway Partnership. Receiver and data processing equipment were loaned to UTIG.

提取得到的二级数据包含三类数据：
1) 位置数据存储于按科考项目整理的.GPX文件中，其中"ICP8"指代2016-2017年度ICECAP2野外科考季，"ICP9"指代2017-2018年度野外科考季。我们推荐使用QGIS或同类平台打开此类文件。每一次声呐浮标（sonobuoy）投放的元数据包含各剖面的唯一标识符，以及投放时刻的飞机经度、纬度、海拔高度和速度（采用东向、北向、天顶向坐标体系）。此外还会标注科考季标识符、航班编号以及剖面唯一标识符。例如在QGIS中，使用"Identify Features"工具点击投放点位即可便捷查看元数据。
2) 剖面数据以可导出数据文件（Exportable Data Files，简称EDF）格式发布，该格式为ASCII格式，包含元数据头部信息与后续的剖面数据。
3) 剖面数据同时以分层数据格式（Hierarchical Data Format，简称HDF）发布，文件扩展名为.h5。提供该格式旨在方便用户借助大量免费可用的Python与MATLAB工具资源，简化剖面数据的导入与分析工作。
4346号项目展示了在东南极洲使用BT-67型巴塞尔飞机搭载机载抛弃式温深计（Airborne eXpendable Bathy-Thermograph，简称AXBT）与机载抛弃式温盐深计（Airborne eXpendable Conductivity, Temperature, Depth，简称AXCTD）传感器开展作业的过程。该项目的核心目标是借助AXBT与AXCTD传感器，推算此前无船舶实测数据区域的海底深度，作业方式通常为将传感器投放至海冰的狭窄冰间水道中。通过探测主要温跃层以获取海洋状态快照则为次要目标。尽管部分传感器由外部资金采购，但由于本项目属于临时附加的机遇性目标，因此开发作业流程与后续数据分析方法的工作未获得专项经费支持。该项目本质上属于原型验证项目，旨在验证能否从高速飞行的飞机上推算狭窄海冰冰间水道下方的海底深度。除8台AXBT传感器外，其余传感器均捐赠给德克萨斯大学地球物理研究所（University of Texas Institute for Geophysics，简称UTIG）；AXCTD传感器由南极门户合作项目采购。接收设备与数据处理设备均借予UTIG。