Davies Reef Automated Marine Weather And Oceanographic Station

This dataset contains meteorological and sea temperature data from the weather station moored in the lagoon on Davies Reef on the Great Barrier Reef. These data are collected to support scientific research at AIMS. Data are made available on request to other researchers and to the public. The weather station is an AIMS Mk3 System.Data recorded: Sea Temperature (4m, 8.5m and 18.5m at MSL), Barometric Pressure, Air Temperature, Solar Radiation (PAR), Wind Direction True (vector averaged), Wind Speed True (30 min average).1. Operation and Weather SensorsThe weather stations collect and store data in electronic memory every half-hour. A central base station calls each remote station regularly using HF radio or telephone lines. The data is transmitted over the radio as a frequency shift keyed signal, organised as packets of information. Errors are detected using parity and check sum methods. Invalid packets are identified by the Base Station, which requests they be sent again. This concept allows recovery of a very high percentage of the data despite poor communications. Remote stations store data for 21 days. Features such as automatic operation, remote control, remote time setting, built in diagnostics, have been developed and incorporated.The sensors are a key part of a weather station. The following are chosen considering the cost, reliability and accuracy.* R.M.Young manufactures the wind sensor, a model number 05103. It is a propeller type with the advantages of being highly linear, highly interchangeable and having a low threshold. Wind direction is measured as the direction the wind is coming from.* The solar radiation sensor is an Under Water Quantum Sensor made by Licor. It measures light in terms of its "Photosynthetically Active Radiation" (PAR). The spectral response is defined and weighted. Drift due to aging of the filters has proven to be a problem, but this applies to similar units too.* Temperature sensors are all Omega Interchangeable Thermistors. These are interchangeable and have high accuracy, but reliability has proven a problem. We are considering alternatives.* The barometric sensor was a modified Aanderaa type on earlier stations. The Mk2 stations were fitted with a Weathertronics Unit. Now all stations are Mk3 stations fitted with a Vaisala barometer which is more interchangeable and more accurate.2. System AccuracySystem accuracy is calculated as the sum of errors caused by: * Calibration * Interchanging sensors * Drift with time * Effects of an ambient temperature range from 0-40 degrees C.The following are the specifications of the sensors used with Mk3 stations. A new sensor suite will be used with Mk5 stations, partly based on the Vaisala WXT510 weather sensor.Both the temperature and wind sensors are interchangeable, and not individually calibrated, though some individual sensors have been checked against standards.* Air Temperature: Interchangeable thermistor and electronics is within +/- 0.4 deg. C, with a 30 seconds settling time in air. There are additional errors due to the aspiration of the temperature screen at low wind speeds.* Water temperature: Interchangeable thermistor and electronics is within +/- 0.4 deg. C, with a 30 minutes settling time in water. A higher precision in situ calibration is normally used (around +/- 0.1 degrees), traceable to a 0.04 degrees standard.* Solar radiation (PAR): +/- 5% of reading. Sensor drift is approximately -4% per year initially.* Barometric pressure: +/- 1 hecto Pascal.* Wind speed: 2% of reading +/- 0.1% FSD.* Wind direction: 2% of reading +/- 0.1% FSD.Electrical settling time for solar radiation and wind parameters is 7 seconds. This is necessary for anti-aliasing filters. Mk1 and Mk2 stations averaged 16 samples over the 16 seconds before logging. Mk3 stations use a continuously averaging software system. The wind readings are vector averaged, so direction is accounted for properly.Calibration procedures and routines are detailed on the Engineering website.3. Wind Sensor SpecificationThe following are additional specifications of the wind sensors used with Mk3 stations. A new sensor will be used with Mk5 stations. Wind sensors are mounted at a nominal 10 meters above water. The R.M. Young sensor has the following characteristics:* Wind SpeedRange: 0-60 m/sPitch: 29.4 cm air passes per rev.Distance constant: 2.7 m for 63% recovery* Wind DirectionRange: 360 deg, with 5 deg electrically open at northDamping ratio: 0.25Delay distance: 1.5 m for 50% recoveryThreshold: 1.0 m/s @ 10 deg.Displacement: 1.5 m/s @ 5 deg. displacement Damped w/length: 7.4 mUndamped w/length: 7.2 m4. Underwater Temperature SensorsThese sensors are interchangeable thermistors in Mk3 stations. They can be mounted a significant distance from the weather station, using a 2 wire connection. The basic accuracy is due to the use of interchangeable units. However improved accuracy is obtained by calibrating against a precision reference sensor in situ. These are in turn calibrated against a standard traceable to 0.04 degrees.

本数据集包含系泊于大堡礁戴维斯礁潟湖内的气象站所采集的气象与海水温度数据，所采集的数据用于支持澳大利亚海洋科学研究所（AIMS）的科学研究。该数据集可应其他研究人员请求及面向公众开放获取。该气象站为AIMS Mk3系统。

所记录的数据包括：平均海平面（Mean Sea Level）下4m、8.5m及18.5m深度的海水温度、大气压力、空气温度、光合有效辐射（Photosynthetically Active Radiation）、真风向（矢量平均）、真风速（30分钟平均值）。

1. 运行与气象传感器
该气象站每半小时采集并将数据存储至电子存储器中。中央基站通过高频无线电（High Frequency，HF）或电话线定期呼叫各远程站。数据以频移键控信号形式通过无线电传输，组织为信息数据包。通过奇偶校验与校验和方法检测传输错误，基站可识别无效数据包并请求重传，该机制可在通信条件不佳的情况下恢复极高比例的有效数据。远程站可存储数据达21天。系统集成了自动运行、远程控制、远程时间设置、内置诊断等功能。

传感器是气象站的核心组件，本次选用的传感器均经过成本、可靠性与精度的综合考量：
- 风速风向传感器由R.M.Young公司制造，型号为05103，为螺旋桨式传感器，具备高线性度、高互换性与低启动阈值的优势。风向测量以风的来向为基准。
- 太阳辐射传感器为Licor公司生产的水下量子传感器，以光合有效辐射为单位测量光照，其光谱响应已定义并加权。滤波器老化导致的漂移已被证实为该类传感器的常见问题，同类产品亦存在该缺陷。
- 温度传感器均为欧米茄（Omega）可互换热敏电阻，具备互换性与高精度，但可靠性存在一定问题，我方目前正考虑备选方案。
- 早期气象站配备的是改装自Aanderaa型号的气压传感器，Mk2型气象站搭载Weathertronics单元。当前所有气象站均为Mk3系统，配备维萨拉（Vaisala）气压计，其互换性与精度均更优。

2. 系统精度
系统精度由以下误差之和计算得出：校准误差、传感器互换误差、随时间产生的漂移误差、环境温度范围0-40℃带来的影响。

以下为Mk3型气象站所用传感器的技术规格。Mk5型气象站将采用全新的传感器套件，部分基于维萨拉WXT510气象传感器。

温度与风速传感器均具备互换性，未进行单独校准，但部分传感器已对照标准进行过校验：
- 空气温度：可互换热敏电阻与电子组件的精度为±0.4℃，在空气中的稳定时间为30秒。低风速下，温度屏蔽罩的抽吸效应会带来额外误差。
- 海水温度：可互换热敏电阻与电子组件的精度为±0.4℃，在水中的稳定时间为30分钟。通常采用原位高精度校准（精度约±0.1℃），该校准可溯源至0.04℃的标准基准。
- 太阳辐射（PAR）：测量误差为读数的±5%，传感器初始年漂移约为-4%。
- 大气压力：±1百帕。
- 风速：误差为读数的2% ±0.1%满量程偏差（Full Scale Deviation，FSD）。
- 风向：误差为读数的2% ±0.1%满量程偏差（Full Scale Deviation，FSD）。

太阳辐射与风速参数的电气稳定时间为7秒，该设置为抗混叠滤波器（anti-aliasing filters）所需。Mk1与Mk2型气象站在记录前会在16秒内对16个采样点取平均，而Mk3型气象站采用持续平均的软件系统。风速读数采用矢量平均方式，可正确计算风向。校准流程与规程详见工程网站。

3. 风速传感器规格
以下为Mk3型气象站所用风速传感器的额外规格参数。Mk5型气象站将采用全新的风速传感器。风速传感器的标称安装高度为距水面10m。R.M.Young型号传感器的特性如下：
- 风速：量程0-60m/s；每转气流通过距离：29.4cm；距离常数：63%响应所需距离为2.7m。
- 风向：量程360°，正北方向电气开路偏差为5°；阻尼比：0.25；50%响应所需延迟距离：1.5m；启动阈值：10°方位下为1.0m/s；位移灵敏度：5°位移下对应1.5m/s；带阻尼的波长长度：7.4m；无阻尼的波长长度：7.2m。

4. 水下温度传感器
Mk3型气象站所用的水下温度传感器为可互换热敏电阻，可通过两线连接方式安装在距离气象站较远的位置。其基础精度源于可互换单元的设计，但通过原位对照精密参考传感器进行校准可获得更高精度，而该参考传感器本身可溯源至精度为0.04℃的标准基准。