RAN CTD Profile Data - HMAS PALUMA ProjectID: HI542PAL_M From: 2013-08-13 To: 2013-10-06

This dataset contains quality controlled vertical profiles of pressure, temperature and salinity measured by a Conductivity, Temperature and Depth (CTD) probe. The dataset contains 43 CTD profiles (casts) obtained during RAN Hydrographic Survey cruise HI542PAL_M from HMAS PALUMA.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（Conductivity, Temperature and Depth, CTD）探针采集得到。本数据集包含43组CTD剖面（测站）数据，采自RAN水文调查航次HI542PAL_M，作业平台为HMAS PALUMA号。该CTD由Applied Microsystems Limited制造，型号为"Micro CTD"，业务中被称为MVP200_CTD。该型CTD搭载四电极镀铂电导池、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传感器每12至18个月由制造商Applied Microsystems Limited进行一次校准：温度传感器采用Hart温度标准校准，压力传感器采用Budenburg静重标准校准，电导传感器则通过Hart温度标准与已知电导率的海水样本完成校准。CTD传感器搭载于鱼形探针之上，该探针由MVP200型电动绞车操控。在下放测次中，探针依靠自重以约2~3 m·s⁻¹的速度自由下落（绞车处于"空转"模式），随后由绞车回收。数据会在下落过程与通常情况下的上升过程中采集，采样率为25 Hz。下放测次的数据质量更高，因为此时传感器流经探针头部的未受扰动海水；而在上升测次中，探针会被翻转（尾部先行），头部的传感器会遭遇来自探针尾部的扰动水流。该型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导致。数据集会通过盐度去尖峰程序对此进行校正，有关盐度去尖峰流程的详细信息，请参阅历史元数据。受绞车与船舶的瞬时升降运动影响，原始CTD压力数据并非始终单调。首先会对原始压力数据进行筛选，得到单调递增的序列，随后以1分巴为压力间隔进行线性插值。最后，通过目视检查以及与平均气候学数据、历史CTD测站数据的比对，为数据添加质量控制标记。