Campbell NR01, Инструкция по эксплуатации

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NR01 Four-Component Net Radiation Sensor
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7.1.3 Expected Measurement Results
The average energy balance at the earth surface strongly depends on the:
•
Latitude (mostly for SW)
•
Local surface properties (SW and LW)
• Local surface temperature (LW)
TABLE 7-3 summarizes the average global values. The average net radiation
at the earth surface is positive, and the remaining energy is used for convective
heat transport and evaporation.
TABLE 7-3. Average Global Radiation Values
at the Earth Surface
Type SW
in
SW
out
SW
net
LW
in
LW
out
LW
net
Net
Units W/m 2 W/m 2 W/m 2 W/m 2 W/m 2 W/m 2 W/m 2
Value 198 –30 168 324* –390** –66 102
*LW
in
value assumes a sky temperature of 2 °C.
**LW
out
value assumes a surface temperature of 14 °C.
The LW radiation values in TABLE 7-3 are corrected for sensor
temperature. The values in TABLE 7-4 are not corrected for
sensor temperature.
On a smaller timescale, the most important factors are:
• solar position
• cloud cover
The ambient air temperature is less important because cloud base temperature
tends to follow surface temperature.
TABLE 7-4 provides the expected outputs. This table makes a distinction
between the day and night (D/N), cloudy and clear (CD / CR) conditions, and
high and low ambient air temperatures.
The raw reading of the upward facing pyrgeometer is generally close to zero
when the sensor temperature is near the ground temperature. Expect small
negative readings when the sensor is above cooled surfaces such as water or
transpiring vegetation, or small positive readings when the surface is emitting
heat (e.g., warm soil at night). The instrument temperature is normally close to
air temperature.
NOTE