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The SO2 determination is slightly more complicated because of the correction needed due to O3 :
where
A2 is the ratio of the SO
SO
A3 is the differential O
(instrument-dependent)
B2 is the extra-terrestrial coefficient for the SO
dependent).
DETERMINING O
AND SO
3
The determination of O
application of an empirical polynomial relation (a numerical "sky chart"). It is assumed that the O
function determined from zenith-sky observations can be analytically related to the value of the
total ozone and the solar zenith angle. The relation assumed has the following form:
2
A
X
B
X
⋅
+
⋅
where
A
a
b
←
+
B
d
e
←
+
C
g
h
←
+
M2 is the path-lengthening factor for the O
F
is the observed zenith-sky value
sky
a, b, c, . . k are site- and instrument-dependent constants
X is the deduced direct-sun O
It must be emphasized that the constants a . . k are NOT factory-set: they can only be determined
after a large number (say 500 or more) of (Fsky, M2, XDS) data triples have been constructed from
pairs of observations made on the direct sun (XDS, M2) and on the zenith sky (Fsky, M2). These
data triples should span the full range of M2 and O
The constants for instrument #15 are quoted here for reference:
a
+0.0164
b
-0.0836
c
+0.0185
Cloudy-sky (ZC) data are treated in the same way as the zenith blue-sky (ZB) observations: this is
only a good approximation for thin cloud; satisfactory treatment of thick-cloud observations awaits
development of an improved cloud-sky relation.
112
MS
B
−
8
MS
←
11
A
2
A
3
M
⋅
⋅
absorption coefficient to the O
2
wavelength combination; A2 is nominally set equal to 2.44
2
absorption coefficient for the SO
3
FROM ZENITH-SKY DATA
2
and SO
amounts from zenith-sky data is accomplished through the
3
2
C
F
+
−
sky
2
M
2
c
M
2
⋅
+
⋅
2
M
2
f
M
2
⋅
+
⋅
2
M
2
k
M
2
⋅
+
⋅
layer
3
value.
3
d
+0.0396
e
+0.6326
f
-0.0705
MKIII OPERATOR'S MANUAL
2
MS
11
−
2
A
2
absorption coefficient of the
3
wavelength combination
2
wavelength combination (instrument-
2
values.
3
g
-0.2778
h
-0.1262
k
-0.0122
3
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