RAN CTD Profile Data - HMAS LEEUWIN ProjectID: HI460(A)LEE_M From: 2009-09-02 To: 2009-09-11

This dataset contains quality controlled vertical profiles of pressure, temperature and salinity measured by a Conductivity, Temperature and Depth (CTD) probe. The dataset contains 182 CTD profiles (casts) obtained during RAN Hydrographic Survey cruise HI460(A)LEE_M from HMAS LEEUWIN.

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，由电导率-温度-深度（Conductivity, Temperature and Depth, CTD）探头采集获取。本数据集包含182组CTD剖面（测站）数据，采集自澳大利亚皇家海军水文调查航次HI460(A)LEE_M，搭载平台为HMAS LEEUWIN号舰艇。

该CTD探头由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，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。其中，温度传感器采用Hart温度标准进行校准，压力传感器采用布登堡活塞式压力校准标准（Budenburg Deadweight）进行校准，电导传感器则结合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型电动绞车控制。在进行下放剖面测量时，探头（业内俗称“鱼体”）依靠自身重量以约2-3米每秒的速度自由下落（此时绞车处于自由轮模式），完成测量后再由绞车收回。数据采集覆盖下放与上浮两个阶段，采样率为25赫兹。下放剖面的数据质量更高，因为此时传感器流经探头前端的未受扰动海水；而上浮阶段探头会被翻转（以尾部先行），前端传感器将遭遇来自尾部的扰动水流。

该型号CTD易于出现“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所引发。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。

原始CTD压力数据受绞车与舰艇的瞬态升降运动影响，并非始终单调递增。对此，首先会对原始压力数据进行子集提取，得到单调递增序列，随后以1分巴（decibar）为间隔进行线性插值。之后，通过目视检查并与平均气候学数据及历史CTD测站数据对比，为数据添加质量控制标记。