RAN CTD Profile Data - HMAS MERMAID ProjectID: SRATD-0030MER_M From: 2011-11-25 To: 2011-12-01

This dataset contains quality controlled vertical profiles of pressure, temperature and salinity measured by a Conductivity, Temperature and Depth (CTD) probe. The dataset contains 2 CTD profiles (casts) obtained during RAN Hydrographic Survey cruise SRATD-0030MER_M from HMAS MERMAID.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，由电导-温度-深度（CTD，Conductivity, Temperature and Depth）探头采集获取。本数据集包含2组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SRATD-0030MER_M，搭载于澳大利亚皇家海军舰艇“美人鱼号”（HMAS MERMAID）之上。本次使用的CTD由Applied Microsystems有限公司制造，型号为“Micro CTD”，该型号CTD在业务中被称为MVP200_CTD。该CTD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。该CTD的传感器每12至18个月由制造商Applied Microsystems有限公司进行一次校准：温度传感器采用Hart温度标准进行校准，压力传感器采用Budenburg活塞压力校准标准进行校准，电导传感器则同时采用Hart温度标准与已知电导率的海水样本进行校准。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。下放测剖面时，探头依靠自身重量以约2-3米每秒的速度自由下落（绞车处于“自由轮”模式），之后由绞车回收。数据分别在下放与回收过程中记录，采样率为25赫兹。下放剖面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；而回收剖面时，探头会翻转（以尾先入的姿态），前端传感器会遭遇来自探头尾部的扰动水流。该型号CTD易出现“盐度尖峰”现象，该现象由温度传感器与电导传感器的响应时间不匹配引发。数据集已通过盐度去尖峰程序对该问题进行校正，有关盐度去尖峰流程的详细信息可查阅历史元数据。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。原始压力数据将被筛选为单调递增序列，随后通过线性插值将数据规整至1分巴（decibar）的压力间隔。随后，通过目视检查以及与平均海洋气候态数据、历史CTD测站数据的比对，为数据添加质量控制标记。