Kipp&Zonen BSRN Scientific Solar Monitoring System User Manual
Page 144
132
Pyrheliometer and Diffuse Geometry Configurations
AC R or Kipp &
Zonen C H 1
K ipp & Zonen 2A P
T racker with C M
series pyranometer
Eppley
SD K
BSR N with Eppley 8-
48 B/W with sim iliarity
to AC R
BSR N with Kipp & Zonen
C M Series pyarnometer
with 2000 design
Instrument Characterisitics
R (m m )
8
25.4
30
28
28
r (m m )
4.8
10.4
15.8
15.8
10.4
L (m m )
183
577
600
641
750
l
z (°)
4
3.5
4.4
3.9
2.9
o
z (°)
2.5
2.5
2.9
2.5
2.1
s
z (°)
1
1.5
1.4
1.1
1.3
Sky irradiances expected from 0º to zl from the centre of the sun under various solar zenith
angles (W m )
-2
0°
2.9
12.8
14.4
12.9
11.2
30°
11.1
11.1
12.4
11.1
9.7
60°
6.3
6.3
7
6.3
5.6
Table C 4.1. Sky irradiances expected from 0º to zl from the centre of the sun under various solar zenith
angles (W m ).
-2
C 4.5
Analytical solutions
Since there is not m uch a problem to assum e a m ean radiance for the range of 1º to 4º for z', the above
consideration can be solved analytically. The both ends on the angle range correspond sloping and
lim iting angles, respectively. An advantage of an analytical consideration is a possibility to be able
to follow the entire process in one equation. Exercises of this kind often provide us an insight into a
new idea. The m ean value for I(z') is designated as
For the sun at the zenith or for pyrheliom eters,
where
Since z can not exceed the lim iting angle and therefore, is very sm all, approxim ating the cosine function
with the polynom ial developm ent, it suffices to take the first two term s, and then