RAN CTD Profile Data - HMAS PALUMA ProjectID: HI580PAL_M From: 2015-09-05 To: 2015-10-15

This dataset contains quality controlled vertical profiles of pressure, temperature and salinity measured by a Conductivity, Temperature and Depth (CTD) probe. The dataset contains 45 CTD profiles (casts) obtained during RAN Hydrographic Survey cruise HI580PAL_M from HMAS PALUMA.The CTD was manufactured by Applied Microsystems Limited and is the "Micro CTD" model. This CTD type is referred to operationally as the MVP200_CTD. This CTD is fitted with a 4 electrode platinized conductivity cell, thermistor temperature sensor and a semiconductor strain gauge pressure sensor.The CTD sensors are calibrated at the manufacturer Applied Microsystems Limited on a 12-18 month schedule. The CTD temperature sensor is calibrated against 'Hart' temperature standards. The pressure sensor is calibrated using 'Budenburg Deadweight' standards. The conductivity sensor is calibrated using 'Hart' temperature standards and seawater samples of known conductivity.The CTD sensors are mounted to a fish-shape probe. The probe is controlled by an electric winch (MVP200 type). For downcasts the fish is allowed to free-fall (winch is in 'free-wheel' mode) under its own weight at about 2-3 ms-1 and then is winched back. Data is recorded in downcast and usually in upcast direction at a sampling rate of 25 Hz. The downcast data is of higher quality because sensors encounter undisturbed seawater that flows through the nose of the fish. On the upcast the fish is flipped around (tail first) and the sensors in the nose encounter disturbed flow from the fish tail.This type of CTD is prone to a phenomenon called 'salinity spiking' caused by a mismatch between the response times of the temperature and conductivity sensor. Data undergoes a salinity de-spiking routine to correct for this. See the history metadata for further details on the salinity de-spiking process.Raw CTD pressure data is not always monotonic due to transient up/down motion of winch/ship. Raw pressure data is subsetted to give a monotonic (increasing) sequence and then linearly interpolated to 1 decibar pressure intervals. Data is then flagged with quality control flags after visual inspection and comparison to average climatology and historical CTD casts.

本数据集包含经质量管控的、由电导率-温度-深度（Conductivity, Temperature and Depth, CTD）探头采集的压力、温度与盐度垂直剖面数据，其中45条CTD剖面（测站）数据采集自RAN水文调查航次HI580PAL_M期间的HMAS PALUMA号。该CTD探头由Applied Microsystems Limited公司制造，型号为"Micro CTD"，业务场景中称其为MVP200_CTD。该CTD搭载四电极镀铂电导率池、热敏电阻式温度传感器以及半导体应变片式压力传感器。CTD传感器由制造商Applied Microsystems Limited按照12~18个月的周期进行校准：温度传感器采用Hart温度标准校准，压力传感器采用Budenburg静重校准标准校准，电导率传感器则结合Hart温度标准与已知电导率的海水样本完成校准。CTD传感器安装于鱼形探头之上，该探头由MVP200型电动绞车操控。下放过程中，探头依靠自重以约2~3 m·s⁻¹的速度自由下落（绞车处于"自由轮"模式），随后通过绞车回收；数据于下放过程中采集，通常也会在上升过程中采集，采样率为25 Hz。下放过程采集的数据质量更高，因为此时传感器流经探头前端的未受扰动海水；上升过程中，探头会被翻转（尾先入水），前端传感器会遭遇来自探头尾部的扰动水流。该类型CTD易出现"盐度尖峰"现象，该现象由温度传感器与电导率传感器的响应时间不匹配引发，数据集已通过盐度去尖峰流程完成校正，有关该流程的详细信息可查阅历史元数据。受绞车与船舶的瞬时升降运动影响，原始CTD压力数据并非始终单调，原始压力数据会被提取为单调递增序列，并通过线性插值处理至1分巴的压力间隔；随后，通过目视检查、与平均气候态数据及历史CTD测站数据对比，为数据赋予质控标记。