RAN CTD Profile Data - HMAS PALUMA ProjectID: HI544PAL_M From: 2014-04-09 To: 2014-06-04

This dataset contains quality controlled vertical profiles of pressure, temperature and salinity measured by a Conductivity, Temperature and Depth (CTD) probe. The dataset contains 76 CTD profiles (casts) obtained during RAN Hydrographic Survey cruise HI544PAL_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压力、温度与盐度垂直剖面数据，此类数据由电导率-温度-深度（Conductivity, Temperature and Depth, CTD）探头采集获得。本数据集涵盖76条CTD剖面（测站）数据，采集自澳大利亚皇家海军（RAN）水文调查航次HI544PAL_M，搭载平台为HMAS PALUMA舰。该CTD探头由Applied Microsystems有限公司制造，型号为“Micro CTD”，作业中被称为MVP200_CTD。该CTD探头配备四电极镀铂电导池、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传感器每12至18个月由制造商Applied Microsystems有限公司开展一次校准：温度传感器采用‘Hart’温度标准进行校准，压力传感器采用‘Budenburg Deadweight’校准标准，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上，该探头由MVP200型电动绞车控制。在下放过程中，鱼形探头依靠自重以约2-3米每秒的速度自由下落（绞车处于“空转轮”模式），之后由绞车收回。数据会在探头下放与通常情况下的上浮过程中记录，采样率为25赫兹。下放过程采集的数据质量更高，因为传感器流经探头头部的未受扰动海水；而上浮过程中探头会被翻转（尾先入水），头部的传感器会遭遇来自探头尾部的扰动水流。此类CTD探头易出现“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，因此数据会经过盐度去尖峰处理流程以修正该问题。有关盐度去尖峰流程的更多细节，请参阅历史元数据。由于绞车与船舶的瞬时升降运动，原始CTD压力数据并非始终单调递增。因此会对原始压力数据进行子集提取，生成单调递增序列，随后通过线性插值将数据插值至1分巴的压力间隔。最后，经目视检查并与平均气候学数据及历史CTD测站数据对比后，为数据添加质量控制标记。