RAN CTD Profile Data - HMAS LEEUWIN ProjectID: HI446(C)LEE_M From: 2009-01-22 To: 2009-02-13

This dataset contains quality controlled vertical profiles of pressure, temperature and salinity measured by a Conductivity, Temperature and Depth (CTD) probe. The dataset contains 26 CTD profiles (casts) obtained during RAN Hydrographic Survey cruise HI446(C)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控制的压力、温度与盐度垂直剖面数据，数据由电导-温度-深度（Conductivity, Temperature and Depth, CTD）探针采集获取。该数据集包含26组CTD测量剖面（测次），采集自HMAS LEEUWIN号执行的RAN水文调查航次HI446(C)LEE_M。本CTD设备由Applied Microsystems Limited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、热敏电阻温度传感器与半导体应变片式压力传感器。CTD传感器由制造商Applied Microsystems Limited按照12至18个月的周期开展校准：温度传感器采用'Hart'温度标准进行校准，压力传感器采用'Budenburg砝码式校准标准'进行校准，电导传感器则同时采用'Hart'温度标准与已知电导率的海水样本完成校准。CTD传感器被安装于鱼形探头上，该探头由MVP200型电动绞车控制。在下行剖面（downcast）测量阶段，探头依靠自身重量以约2~3 m·s⁻¹的速度自由下落（此时绞车处于"自由滑转模式（free-wheel mode）"），完成下行后通过绞车回收上行。数据会在下行剖面（downcast）阶段及通常在上行剖面（upcast）阶段进行记录，采样率为25 Hz。下行剖面（downcast）数据质量更优，因此时传感器流经未受扰动的海水，水流从探头鼻部流过；而上行剖面（upcast）阶段，探头会被翻转（以尾部先行），此时鼻部传感器会遭遇来自探头尾部的扰动水流。此类CTD设备易出现"盐度尖峰（salinity spiking）"现象，该现象由温度与电导传感器响应时间不匹配引发。数据集将经过盐度去尖峰处理流程以校正该问题，相关细节可参见历史元数据。原始CTD压力数据并非单调序列，系绞车与船舶存在瞬态升降运动所致。因此需对原始压力数据进行子集选取，得到单调递增序列，随后以1分巴（decibar, dbar）为间隔进行线性插值。最终，经目视检查、与平均海洋气候学数据及历史CTD测次对比后，为所有数据添加质量控制标记。