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ET107 Weather Station
7
FIGURE 5-1. Effect of structure on wind flow
5.1.2 Temperature and Relative Humidity
Sensors should be located over an open, level area at least 9 m (29.5 ft) (EPA)
in diameter. The surface should be covered by short grass, or where grass does
not grow, the natural earth surface. Sensors should be located at a distance of at
least four times the height of any nearby obstruction and at least 30 m
(98.43 ft) (EPA) from large paved areas. Sensors should be protected from
thermal radiation and adequately ventilated.
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
5.1.3 Solar Radiation
Pyranometers should be located to avoid shadows on the sensor at any time.
Mounting it on the southernmost (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.