Guidelines for Professional Sensor Siting
AcuRite sensors are sensitive to surrounding conditions. Proper placement of digital displays and outdoor sensors is critical to the accuracy and performance of the product. Sensors should be installed in the way that best captures the weather data that is most important to you. When comparing your weather station's data against another local source, it's important to compare against a weather station that is using a sensor positioned at the same mounting height.
Professional weather station installations follow a stringent set of standards for sensor siting and mounting. The following information is an excerpt from National Weather Service publications on sensor siting.
Sensor Siting Requirements
To obtain data representative of a station's surroundings, local conditions must not be artificially influenced by surrounding materials and/or obstructions (e.g., concrete, buildings, snow, etc). The sensor exposure will strive to minimize or eliminate the effects of manmade or geographical obstructions. Sensors should be located as far as practicable from cultivated land to reduce contamination by dust and dirt. The following sensor siting requirements are adopted from the Office of the Federal Coordinator for Meteorology (OFCM) standards, with which all federal agencies, including the NWS, comply.
Temperature & Relative Humidity Measurement
» Standard mounting elevation is 4.0 to 6.5 feet (1.2 to 2.0 meters) above grade.
» The sensor should be mounted over a plot of open level ground at least 30 feet (9 meters) in diameter. The ground beneath the sensor should be short grass or natural earth, not asphalt, concrete, areas of standing water, etc.
» The distance between the sensor and any obstruction should be at least 4 times the height of the obstruction (40 meters for a 10-meter obstruction). It should be at least 100 feet (30meters) from large paved areas, and not close to steep slopes.
» If mounted on a tower, the sensor should be on a tower boom at least as long as the tower diameter.
» The standard mounting elevation is 30 - 33 feet (9 - 10 meters) above the ground in open, level terrain. Small gradual slopes are acceptable.
» A horizontal distance of ten times the height of an obstruction should be maintained, between the wind sensor and the obstruction, for the surrounding area to be considered open terrain. An obstruction can be manmade (building) or natural (tree).
» If the sensor is to be mounted on the roof of a building, it should be mounted at a height of 20 feet (6 meters) above the highest structure. This is to remove the sensor from the area in which the air flow is affected by the building. For tall buildings where this guideline cannot be met, a 10 to 15 foot (3 to 5 meter) mast should be mounted on the side of the building with the prevailing wind.
» If the sensor is to be mounted on a tower, the sensor should be above the tower or on a boom. The boom should be twice as long as the maximum diameter or diagonal of the tower, and should be directed into the prevailing wind.
Rain Gauge Siting
Rain gauge exposure is critical to obtain accurate measurements. Gauges should not be located close to isolated obstructions, like trees and buildings, which may deflect precipitation due to erratic turbulence. To avoid wind and resulting turbulence problems, do not locate gauges in wide-open spaces or on elevated sites, such as the tops of buildings.
The best site for a gauge is one in which it is protected in all directions, such as in an opening in a grove of trees. The height of the protection should not exceed twice its distance from the gauge. As a general rule, the windier the gauge location is, the greater the precipitation error will be.
Egan, Kathleen, and Seth Baldelli. "Guidelines for Meteorological Sensor Siting and Meteorological Sensor Height Measurements." Jan. 2008. PDF file.
NOAA National Weather Service, Office of Climate, Water and Weather Services. (2013, June 21). Proper Siting. nws.noaa.gov. Retrieved Sept 20, 2013, from http://www.nws.noaa.gov/om/coop/standard.htm.