Section 1. Preparation and Siting
Standard measurement heights:
1.5m ± 1.0 m (AASC)
1.25- 2.0 m (WMO)
2.0m temperature (EPA)
2.0m and 10.0 m for temperature difference (EPA)
1.3.3Precipitation
A rain gage should be sited on level ground that is covered with short grass or gravel. In open areas, the distance to obstructions should be two to four times (EPA, AASC) the height of the obstruction.
The height of the opening should be as low as possible, but should be high enough to avoid splashing from the ground. Wind shields, such as those used by the National Weather Service, are recommended for open areas.
Collectors should be heated, if necessary, to properly measure frozen precipitation. The gage must be mounted above the average level of snow accumulation in areas that experience significant snowfall.
Standard measurement heights:
1.0 m ± 1.0 cm (AASC)
30.0cm minimum (WMO, EPA)
1.3.4Solar Radiation
Pyranometers should be located to avoid shadows on the sensor at any time. Mounting it on the southern most (northern hemisphere) portion of the weather station will minimize the chance of shading from other weather station structures. Reflective surfaces and sources of artificial radiation should be avoided. The height at which the sensor is mounted is not critical.
1.3.5 Soil Temperature
The measurement site for soil temperature should be at least 1 m2 and typical of the surface of interest. The ground surface should be level with respect to the immediate area (10 m radius).
Standard measurement depths:
10.0 cm ± 1.0 cm (AASC)
5.0 cm, 10.0 cm, 50.0 cm, 100.0 cm (WMO)