PWS100 Present Weather Sensor - Campbell Scientific
PWS100 Present Weather Sensor - Campbell Scientific
PWS100 Present Weather Sensor - Campbell Scientific
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Section 6. Installation<br />
6.1 Location and Orientation<br />
The <strong>PWS100</strong> measures environmental variables and is designed to be located<br />
in harsh weather conditions. However there are a few considerations to take<br />
into account if accurate and representative data from a site are to be obtained.<br />
NOTE<br />
The descriptions in this section are not exhaustive. Please refer to<br />
meteorological publications for further information on the<br />
locating of weather instruments.<br />
The <strong>PWS100</strong> should be sited in a position representative of local weather<br />
conditions and not of a specific microclimate (unless the analysis of<br />
microclimate weather is being sought).<br />
To give non-microclimatic measurements the <strong>PWS100</strong> should be sited away<br />
from possible physical obstructions that could affect the fall of precipitation.<br />
The <strong>PWS100</strong> should also be positioned away from sources of heat, electrical<br />
interference and in such a position as to not have direct light on the sensor<br />
lenses.<br />
Whenever possible, the <strong>PWS100</strong> should be located away from windbreaks.<br />
Several zones have been identified upwind and downwind of a windbreak in<br />
which the airflow is unrepresentative of the general speed and direction. Eddies<br />
are generated in the lee of the windbreak and air is displaced upwind of it. The<br />
height and depth of these affected zones varies with the height and to some<br />
extent the density of the obstacle.<br />
Generally, a structure disturbs the airflow in an upwind direction for a distance<br />
of about twice the height of the structure, and in a downwind direction for a<br />
distance of about six times the height. The airflow is also affected to a vertical<br />
distance of about twice the height of the structure. Ideally, therefore, the<br />
<strong>PWS100</strong> should be located outside this zone of influence in order to obtain<br />
representative values for the region (see Figure 6-1).<br />
FIGURE 6-1. Effect of structure on air flow<br />
6-1