Campbell Scientific ET106 ETo Station - Manual (Page 9)

Section 1. Preparation and Siting
1-5
1.3 Siting and Exposure
If any part of the weather station comes in contact with
power lines, you could be killed. Contact local utilities for
the location of buried utility lines before digging or driving
ground rods.
Selecting an appropriate site for the weather station is critical in order to obtain
accurate meteorological data. In general, the site should be representative of
the general area of interest, and away from the influence of obstructions such as
buildings and trees.
The weather station should not be located where sprinkler irrigation water will
strike sensors or instrument enclosure.
Some general guidelines for site selection are listed below, which were
condensed from EPA (1988)
1
, WMO (1983)
2
, and AASC (1985)
3
publications.
1.3.1 Wind Speed and Direction
Wind sensors should be located over open level terrain, and at a distance of at
least ten times (EPA) the height of any nearby building, tree or other
obstruction, as illustrated in Figure 1.3-1.
Standard measurement heights:
3.0 m ± 0.1 m recommended (AASC)
2.0 m ± 0.1 m, 10.0 m ± 0.5 m optional (AASC)
10.0 m (WMO and EPA)
1.3.2 Temperature and Relative Humidity
Sensors should be located over an open level area at least 9 m (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 (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
CAUTION