Automatic weather station
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automatic weather station
(¦öd·ə¦mad·ik ′weth·ər ′stā·shən)
(meteorology) A weather station at which the services of an observer are not required; usually equipped with telemetric apparatus.
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Automatic weather station
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Automatic weather station
An automatic weather station (AWS) is an automated version of the traditional weather station, either to save human labour or to enable measurements from remote areas.[1] An AWS will typically consist of a weather-proof enclosure containing the data logger, rechargeable battery, telemetry (optional) and the meteorological sensors with an attached solar panel or wind turbine and mounted upon a mast. The specific configuration may vary due to the purpose of the system.[1] The system may report in near real time via the Argos System and the Global Telecommunications System,[2] or save the data for later recovery.[3] In the past, automatic weather stations were often placed where electricity and communication lines were available. Nowadays, the solar panel, wind turbine and mobile phone technology have made it possible to have wireless stations that are not connected to the electrical grid or telecommunications network.[4]
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Sensors
Most automatic weather stations have[1][5]
- Thermometer for measuring temperature
- Anemometer for measuring wind speed
- Wind vane for measuring wind direction
- Hygrometer for measuring humidity
- Barometer for measuring atmospheric pressure
Some of them even have[4]
- Ceilometer for measuring cloud height
- Rain gauge for measuring rainfall
- Present weather sensor and/or visibility sensor
Unlike manual weather stations, automatic weather stations cannot report the class and amount of clouds. Also, precipitation measurements are difficult, especially for snow, as the gauge must empty itself between observations. For present weather, all phenomena that do not touch the sensor, such as fog patches, remain unobserved.[1] The change from manual observations to automatic weather stations is a major non-climatic change in the climate record.[6] The change in instrumentation, enclosure and location can lead to a jump in, for example, the measured temperature or precipitation values, which can lead to erroneous estimates of climate trends. This change, and related non-climatic changes, have to be removed by homogenization.
Enclosures
Enclosures used with automatic weather stations are typically weather proof fiberglass, ABS or stainless steel, With ABS being the cheapest, stainless steel the most durable and fiberglass being a compromise[1]
Power supply
The main power source for an automatic weather station is usually one or more solar panels connected in parallel with a regulator and one or more rechargeable batteries. As a rule of thumb, solar output is at its optimum for only 5 hours each day. As such, mounting angle and position are vital. In the Northern Hemisphere the solar panel would be mounted facing south and vice versa for the Southern Hemisphere. The output from the solar panels may be supplemented by a wind turbine to provide power during periods of poor sunlight, or by direct connection to the local electrical grid.[4]
Mast
The standard mast heights used with automatic weather stations are 2, 3, 10 and 30 meters. Other sizes are available, but typically these sizes have been used as standards for differing applications.[1]
- The 2 meter (6.6 feet) mast is used for the measurement of parameters that affect a human subject. The mast height is referenced to head height.
- The 3 meter (9.8 feet) mast is used for the measurement of parameters that affect crops (such as wheat, sugar cane etc.) The mast height is referenced to crop top.
- The 10 meter (32.8 feet) mast is used for the measurement of parameters without interference from objects such as trees, buildings or other obstructions. Typically the most important weather parameter measured at this height is wind speed and direction.
- The 30 meter (98.4 feet) mast is used for the measurement of parameters over stratified distances for the purposes of data modelling. A common application is to take measurements of wind, humidity and temperature at 30, 10, and 2 meters. Other sensors are mounted around the 2 meter or lower height.
See also
References
- ^ a b c d e f King, Jeremy. "Automatic Weather Stations". http://www.automaticweatherstation.com/index.html. Retrieved 2009-04-15.
- ^ "About the Automatic Weather Station project". Automatic Weather Station project. The National Science Foundation Office of Polar Programs. http://uwamrc.ssec.wisc.edu/aboutaws.html. Retrieved 2009-04-15.[dead link]
- ^ "ADDI Automatic weather stations". ADDI. http://www.aadi.no/Aanderaa/Products/AWS/default.aspx. Retrieved 2009-04-15.
- ^ a b c "Automatic Weather Stations for Agricultural". Australian Bureau of Meteorology. http://www.bom.gov.au/inside/services_policy/pub_ag/aws/aws.shtml. Retrieved 2009-04-15.
- ^ "North Hants Weather - AWS". http://www.northantsweather.org.uk/weathertour/aws.htm. Retrieved 2009-04-15.
- ^ Begert, M., Schlegel, T., and Kirchhofer, W.: Homogeneous temperature and precipitation series of Switzerland from 1864 to 2000. Int. J. Climatol., 25, 65–80, 2005.
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