RAN CTD Profile Data - HMAS BENALLA ProjectID: HI537BEN_M From: 2013-06-20 To: 2013-07-16

This dataset contains quality controlled vertical profiles of pressure, temperature and salinity measured by a Conductivity, Temperature and Depth (CTD) probe. The dataset contains 312 CTD profiles (casts) obtained during RAN Hydrographic Survey cruise HI537BEN_M from HMAS BENALLA.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控制的压力、温度与盐度垂直剖面数据，数据由温盐深仪（Conductivity, Temperature and Depth, CTD）采集获取。该数据集包含312条CTD剖面（测站），数据采集自澳大利亚皇家海军（Royal Australian Navy, RAN）水文勘测航次HI537BEN_M，搭载平台为HMAS本阿拉号（HMAS BENALLA）。本次使用的CTD由应用微系统有限公司（Applied Microsystems Limited）制造，型号为"Micro CTD"，该型号CTD在作业中被称为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。CTD传感器由制造商应用微系统有限公司按照12至18个月的周期开展校准工作：温度传感器采用哈特（Hart）温度校准标准进行校准，压力传感器采用布登伯格活塞式压力校准标准（Budenburg Deadweight）进行校准，电导率传感器则结合哈特温度校准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。下放剖面时，探头依靠自身重量以约2至3米每秒的速度自由下落（绞车处于"free-wheel"模式），完成下放后通过绞车回收。数据在下放剖面方向及通常在回收剖面方向进行采集，采样率为25赫兹。下放剖面的数据质量更高，因为传感器流经探头前端未受扰动的海水；而回收剖面时探头会翻转（尾端先行），前端传感器会遭遇来自探头尾部的扰动水流。该类型CTD易出现盐度尖峰效应（salinity spiking），该现象由温度与电导率传感器的响应时间不匹配导致。为此，数据集已通过盐度去尖峰校正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参见历史元数据。原始CTD压力数据并非始终单调，这是由绞车与船舶的瞬态升降运动导致的。首先对原始压力数据进行子集提取，得到单调递增的压力序列，随后以1分巴（decibar）为压力间隔对其进行线性插值。经目视检查、与海洋气候平均场及历史CTD测站数据对比后，为各数据添加质量控制标记。