Campbell CVF4 Specifiche Scaricare il pdf (Pagina 19)

CNR4 Net Radiometer

In the equation above, E is calculated according to the Equation 5-1.

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.

5.5 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) (5-4)

In the equation above, E is calculated according to Equation 5-1.

Net short-wave solar radiation will always be positive. This can be used as a

tool for quality assurance of your measured data.

5.6 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) (5-5)

In the equation above, E is calculated according to Equation 5-2. According to

equation 5-5 above, the terms that contain the sensor body temperature T

cancel each other. Therefore, if one is 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".

4/1

1067.5

⎥

⎦

⎤

⎢

⎣

⎡

⋅

−

rPyrgeometeupper E

atureSky temper

(5-6)

4/1

1067.5

⎥

⎦

⎤

⎢

⎣

⎡

⋅

−

rPyrgeometelower E

eTemperatur Ground

(5-7)

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

exchange of radiative energy (infinite objects):

1 degree of temperature difference = 5 W/m

(rule of thumb)

1 2 ... 14 15 16 17 18 19 20 21 22 23 24 ... 59 60

Commenti su questo manuale

Nessun commento

Campbell CVF4 Specifiche Pagina 19

Commenti su questo manuale

Prodotti e manuali riguardandi Misurazione, test & controllo Campbell CVF4