Campbell CNR4, Руководство по эксплуатации продукта

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CNR4 Net Radiometer
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In Equation 8-3 , E is calculated according to the Equation 8-1 .
Albedo will always be smaller than 1. Checking this can be used as a tool for
quality assurance of your data. If you know the approximate albedo at your
site, the calculation of albedo can also serve as a tool for quality control of your
measured data at a specific site.
8.5 Calculation of Net Short-wave Radiation
The net short-wave solar radiation is equal to the incoming (downwelling)
short-wave radiation minus the reflected (upwelling) short-wave radiation.
Net Short-wave Radiation = (E upper Pyranometer)
– (E lower Pyranometer)
(8-4)
In Equation 8-4 , E is calculated according to Equation 8-1 .
Net short-wave solar radiation will always be positive. This can be used as a
tool for quality assurance of your measured data.
8.6 Calculation of Net Long-wave Radiation
The net long-wave far infrared radiation is the part that contributes to heating
or cooling of the earth’s surface. In practice, usually the net long-wave far
infrared radiation will be negative.
Net Long-wave Radiation = (E upper Pyrgeometer)
– (E lower Pyrgeometer)
(8-5)
In Equation 8-5 , E is calculated according to Equation 8-2 . According to
Equation 8-5 , the terms that contain the sensor body temperature, T, cancel
each other. Therefore, if only interested in the net long-wave radiation, instead
of separate upper and lower components of the long-wave radiation, the CNR4
temperature measurement is not required.
The E measured with the pyrgeometer actually represents the irradiance of the
sky (for upward-facing pyrgeometer) or the ground (for downward-facing
pyrgeometer). Assuming that these two, ground and sky, behave like perfect
blackbodies, theoretically, one can calculate an effective sky temperature and
an effective ground temperature.
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10 67 . 5
r Pyrgeomete upper E
e Temperatur Sky






⋅
=
−
(8-6)
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8
10 67 . 5




⋅
=
−
r Pyrgeomete lower E
e Temperatur Ground (8-7)
As a rule of thumb, for ambient temperatures of about 20 degrees Celsius, one
can say that one degree of temperature difference between two objects results
in a 5 W/m 2 exchange of radiative energy (infinite objects):
1 degree of temperature difference = 5 W/m 2 (rule of thumb)