Dataset: Agincourt Reef Automated Marine Weather and Oceanographic Station


This dataset contains meteorological data from Agincourt Reef, Great Barrier Reef, from November 1989 with breaks. The weather station is located on Quicksilver's northern pontoon.\n These data are collected to support scientific research at AIMS. Data are made available on request to other researchers and to the public.\n The weather station is an AIMS Mk3 System. \n \nData recorded: Sea Temperature (1m and 10m at MSL), Barometric Pressure, Air Temperature, Solar Radiation (PAR), Wind Direction True (vector averaged), Wind Speed True (30 min average). \n \nThis weather station has been deployed in three different locations on Agincourt Reef. \nLocation 1: -15.9617, 145.8225 from November 1989 to 1996 \nLocation 2: -16.0381, 145.8325 from 1996 to October 2000 \nLocation 3: -16.033, 145.817 from October 2000 to present. \n \n1. Operation and Weather Sensors \n \nThe 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. \n \nThe sensors are a key part of a weather station. The following are chosen considering the cost, reliability and accuracy. \n* 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. \n* 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. \n* Temperature sensors are all Omega Interchangeable Thermistors. These are interchangeable and have high accuracy, but reliability has proven a problem. We are considering alternatives. \n* 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. \n \n2. System Accuracy \n \nSystem accuracy is calculated as the sum of errors caused by: \n * Calibration \n * Interchanging sensors \n * Drift with time \n * Effects of an ambient temperature range from 0-40 degrees C. \n \nThe 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. \n \nBoth the temperature and wind sensors are interchangeable, and not individually calibrated, though some individual sensors have been checked against standards. \n \n* 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. \n* 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. \n* Solar radiation (PAR): +/- 5% of reading. Sensor drift is approximately -4% per year initially. \n* Barometric pressure: +/- 1 hecto Pascal. \n* Wind speed: 2% of reading +/- 0.1% FSD. \n* Wind direction: 2% of reading +/- 0.1% FSD. \n \nElectrical 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. \n \nCalibration procedures and routines are detailed on the Engineering website. \n \n3. Wind Sensor Specification \n \nThe 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. \n \nThe R.M. Young sensor has the following characteristics: \n* Wind Speed \nRange: 0-60 m/s \nPitch: 29.4 cm air passes per rev. \nDistance constant: 2.7 m for 63% recovery \n* Wind Direction \nRange: 360 deg, with 5 deg electrically open at north \nDamping ratio: 0.25 \nDelay distance: 1.5 m for 50% recovery \nThreshold: 1.0 m/s @ 10 deg. \nDisplacement: 1.5 m/s @ 5 deg. displacement \nDamped w/length: 7.4 m \nUndamped w/length: 7.2 m \n \n4. Underwater Temperature Sensors \n \nThese 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.\n

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