Instruction manual

WS-PRO2 Weather Station Manual
GT
27176
Page 11 of 61
• Shaded areas
• Swamps
• Areas where snow drifts occur
• Low places holding standing water after rains
2.1.3 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.
2.1.4 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.
2.1.5 Soil Temperature
The measurement site for soil temperature should be at least 1 square
meter 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)
2.1.6 Determining True North for Wind Vane Orientation
Magnetic declination, or other methods to find True North, should be
determined prior to installing the weather station. True North is usually
found by reading a magnetic compass and applying the correction for
magnetic declination*; where magnetic declination is the number of
degrees between True North and Magnetic North. Magnetic declination
for a specific site can be obtained from a USFA map, local airport, or
through an internet service called NSSDC CGM (Section 2.1.7). A
general map showing magnetic declination for the contiguous United
States is shown in Figure 5.
Declination angles east of True North are considered negative, and are
subtracted from 0 degrees to get True North as shown Figure 8.
Declination angles west of True North are considered positive, and are
added to 0 degrees to get True North as shown in Figure 9. For example,