RAN CTD Profile Data - HMAS LEEUWIN ProjectID: HI488LEE_M From: 2011-01-11 To: 2011-01-11

This dataset contains quality controlled vertical profiles of pressure, temperature and salinity measured by a Conductivity, Temperature and Depth (CTD) probe. The dataset contains 1 CTD profiles (casts) obtained during RAN Hydrographic Survey cruise HI488LEE_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、温度及盐度垂直剖面数据，由电导-温度-深度（Conductivity, Temperature and Depth，CTD）探针实测获取。该数据集收录了澳大利亚皇家海军水文调查航次HI488LEE_M期间，由澳大利亚皇家海军舰艇HMAS LEEUWIN号执行的1组CTD测剖面数据。

本次使用的CTD探针由Applied Microsystems Limited公司制造，型号为"Micro CTD"。该型号在业务场景中被称为MVP200_CTD。该CTD搭载四电极镀铂电导池、热敏电阻式温度传感器及半导体应变片式压力传感器。

CTD传感器每12至18个月将由制造商Applied Microsystems Limited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"Budenburg Deadweight"标准完成校准，电导传感器则结合"Hart"温度标准与已知电导率的海水样本实施校准。

CTD传感器被安装于鱼形探针之上，该探针由MVP200型电动绞车操控。在下行测剖面阶段，探针依靠自重以约2~3米每秒的速度自由下落（绞车处于"自由滑行"模式），随后通过绞车回收。数据会在下行与上行测剖面阶段进行记录，采样率为25赫兹。下行测剖面的数据质量更高，因为此时传感器流经的是未受扰动的海水，水流从探针头部流过；而上行测剖面阶段，探针会被翻转（尾部先行），头部传感器将流经来自探针尾部的扰动水流。

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流程对该问题进行校正，有关盐度去尖峰处理的详细信息可参见历史元数据。

原始CTD压力数据并非始终单调，这是由于绞车与船舶存在瞬时升降运动。原始压力数据将被筛选为单调递增序列，并通过线性插值得到1分巴的压力间隔数据。随后，研究人员将通过目视检查、与平均气候学数据及历史CTD测剖面对比，为数据赋予质量控制标记。