Wind, air temperature, and water vapor pressure measurements are affected by surface type and roughness, soil moisture, regional topography, and obstructions. Sites selected for their applicability to a broader area should be free from obstructions such as buildings, trees, and steep slopes. Ten meter towers are often used to raise measurement heights above low-lying obstructions. The following table lists the suggested measurement heights and exposure (distance to an obstruction) for each type of sensor.
| Wind | 3 m ±0.1 m recommended (AASC) 2 m ±0.1 m, 10 m ±0.5 m, optional (AASC) 10 m (WMO & EPA) | No closer than ten times the obstruction's height |
| Air Temperature & Relative Humidity | 1.5 m ± 1 m (AASC) 1.25-2.0 m (WMO) 2.0 m for temperature only (EPA) 2 m & 10 m for temperature difference (EPA) | The sensor must be housed in a ventilated radiation shield to protect the sensor from thermal radiation. The EPA recommends the sensor be no closer than four times the obstruction's height and at least 30 m from large paved areas. |
| Solar Radiation | Height should be consistent with the exposure standard (AASC, WMO, EPA). To facilitate leveling/cleaning, CSI recommends installing at a height of 3 m or less. | The sky should not be blocked by any surrounding object. However, objects <10° above the horizontal plane of the sensor are allowed. |
| Precipitation | 1.0 m ±0.2 m (AASC) 30 cm minimum (WMO) | AASC & EPA suggest the sensor be no closer than four times the obstruction's height. The orifice of the gage must be in a horizontal plane, open to the sky, and above the level of in-splashing and snow accumulation. |
| Soil Temperature | 10 cm ±1.0 cm (AASC) 5 cm, 10 cm, 20 cm, 50 cm, 100 cm (WMO) | Measurement site should be 1 m² and typical of the surface of interest. The ground surface should be level with respect to the immediate (10 m radius) area. |
References |
| The State Climatologist (1985) Publication of the American Association of State Climatologists: Heights and Exposure Standards for Sensors on Automated Weather Stations, v. 9, No. 4 October, 1985. |
| EPA (1987). On-Site Meteorological Program Guidance for Regulatory Modeling Applications, EPA-450/4-87-013. Office of Air Quality Planning and Standards, Research Triangle Parks, North Carolina 27711. |
| WMO (1983). Guide to Meteorological Instruments and Methods of Observation. World Meteorological Organization No. 8, 5th edition, Geneva Switzerland. |
| Tanner, Bertrand D. (1990). Automated Weather Stations, Remote Sensing Reviews, 1990, Vol. 5 (1), p.73-98. |