RAN CTD Profile Data - HMAS MELVILLE ProjectID: HI548MEL_M From: 2013-10-14 To: 2013-11-12

This dataset contains quality controlled vertical profiles of pressure, temperature and salinity measured by a Conductivity, Temperature and Depth (CTD) probe. The dataset contains 409 CTD profiles (casts) obtained during RAN Hydrographic Survey cruise HI548MEL_M from HMAS MELVILLE.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，均由电导-温度-深度（Conductivity, Temperature and Depth, CTD）探针采集得到。本数据集共包含409组CTD剖面（单次下放测量），采集自澳大利亚皇家海军（Royal Australian Navy, RAN）水文调查航次HI548MEL_M，搭载于HMAS MELVILLE号舰艇。该CTD探针由Applied Microsystems Limited公司制造，型号为"Micro CTD"，此类CTD在作业中被称为MVP200_CTD。该CTD搭载有四电极镀铂电导池、热敏电阻温度传感器以及半导体应变片式压力传感器。
该CTD传感器由制造商Applied Microsystems Limited按照12至18个月的周期进行校准：其温度传感器采用'Hart'温度标准进行校准，压力传感器采用'Budenburg Deadweight'标准校准，电导传感器则采用'Hart'温度标准与已知电导率的海水样本进行校准。CTD传感器被安装于鱼形探针（fish-shape probe），该探针由型号为MVP200的电动绞车操控。在下行测量时，探针依靠自身重量以约2~3 m·s⁻¹的速度自由下落（绞车处于"空转轮"模式），随后通过绞车回收。数据通常在下行与上行测程中均被记录，采样率为25 Hz。
下行测量数据的质量更高，因为传感器流经的是未受扰动的海水，水流从探针头部流过。上行测量时，探针会被翻转（尾部先行），此时头部的传感器会流经来自探针尾部的扰动水流。此类CTD易出现一种名为盐度尖峰（salinity spiking）的现象，该现象由温度与电导传感器的响应时间不匹配所引发。数据集将通过盐度去尖峰程序对该效应进行校正，有关盐度去尖峰流程的详细信息，请参阅历史元数据。
由于绞车与船舶的瞬态升降运动，原始CTD压力数据并非始终单调递增。原始压力数据会被截取为单调递增序列，随后以1分巴（decibar, dbar）为压力间隔进行线性插值。经过目视检查、与平均气候学数据及历史CTD测站剖面对比后，数据会被标记质量控制标识。