Kipp&Zonen CNR 4 Net Radiometers - Manual (Page 14)

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1.1.6.6 Calculation of the Net (total) radiation
The Net radiation, NR, can be calculated using all 4 sensor measurement results:
NR = (E upper pyranometer) + (E upper pyrgeometer) - (E lower pyranometer) - (E lower pyrgeometer)
(1.8)
Where E is the irradiance that is calculated for the pyranometer according to equation 1.1, for the pyrgeometer
according to equation 1.2. the terms with T cancel from this equation.
1.2
CNR 4 Performance under different conditions
Below, table 1.3, shows an indication of what you might typically expect to measure under different meteorological
conditions. The first parameter is day and night. At night, the Solar radiation is zero. The second column indicates if
it is cloudy or clear. A cloud acts like a blanket, absorbing part of the Solar radiation, and keeping Net Far Infrared
radiation close to zero. The third parameter is ambient temperature. This is included to show that the "sky
temperature" (column nine) tracks the ambient temperature. Under cloudy conditions this is logical; cloud bases will
be colder than the ambient temperature at instrument level, the temperature difference depends roughly on cloud
altitude.
Under clear sky conditions it is less obvious that sky temperature "adjusts" to the ambient temperature. This can
roughly be attributed to the water vapour in the air, which is a major contributor to the Far Infrared radiation.
Fig. 1.2.1 Different measurement conditions and signals
Fully clouded Sunny, partly clouded Clear and Sunny
Values calculated using:
Werte, errechnet aus Formel:
Calcul des valeurs à l'aide:
Utilizar valores calculados:
Upper
Oben • Supérieur • Superior
Lower
50 ... 120 W/m²
0 ... 50 W/m²
120 ... 500 W/m²
50 ... 200 W/m²
500 ... 1000 W/m²
200 ... 400 W/m²
Unten • Inférieur • Más bajo
Bewölkt
Très nuageux
Totalmente Nublado
Sonnig, teils bewölkt
Ensoleillé, un peu nuageux
Parcialmente nublado
Klarer Himmel und sonnig
Clair et ensoleillé
Cielo despejado
=
0 ... -10 W/m²
-25 ... 25 W/m²
-10 ... -50 W/m²
-25 ... 25 W/m²
-50 ... -150 W/m²
-25 ... 25 W/m²
Upper
Oben • Supérieur • Superior
Lower
Unten • Inférieur • Más bajo
Pyranometer
Pyrgeometer