Specifications

Section 1. General

Situations to avoid include:

• large industrial heat sources

• rooftops

• steep slopes

• sheltered hollows

• high vegetation

• shaded areas

• swamps

• areas where snow drifts occur

• low places holding standing water after rains

Standard measurement heights:

1.5 m ± 1.0 m (AASC)

1.25 - 2.0 m (WMO)

2.0 m temperature (EPA)

2.0 m and 10.0 m for temperature difference (EPA)

1.3.3 Precipitation

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)

30.0 cm minimum (WMO, EPA)

1.3.4 Solar 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 m

and typical of

the surface of interest. The ground surface should be level with respect to the

immediate area (10 m radius).

1-4