309 
HOOELLERCEBNIS 
Pyranometer 
of global 
= AL = 57. 
KWHM 
-2 
PYRANOHETERHESSUNG IN KWHM 
(PYRANOMETER MEASUREMENT) 
= 5.57 kWh/m 3 = 2005 J/cm 2 
<y = 0.52 kWh/m 3 
Fig. 4.3: Intercomparison between ground-based 
measurements and model results 
satellite: lieteosat time: June 1983 
here: monthly means of the daily sums 
<M ad >: mean daily sum, a: mean error (rms) 
Pyranometer 
measurements 
<M Qa > = 1780 J/cm : 
a = 110 J/cm 3 
Fig. 4.5: The same as for Fig. 4.4.b, but here 
area: Asia 
4. Results 
Figs. 4.1 and 4.2 reveal maps of monthly averages 
of daily sums (a), normalized values (b) of these 
monthly averages of daily sums as calculated from 
measurements of the satellites Meteosat (June 1983) 
and GMS (July 1983). All maps are displayed in 
•\.M( 3c ,> — 1303 J/cm 3 o' — 110 J/cm 3 
pyranometer 
measurements 
(J/cm 3 ) 
ground-based 
J/cm 3 
Fig. 4.4: Intercomparison between 
measurements and model results 
satellite: GMS time: July 1983 
area: Australia 
(a) daily sums of global radiation 
(b) monthly means of the daily sums 
black and white tones. They show considerable 
details due either to orographically or dynamically 
induced cloud fields. See for example the mountain 
regions in Eastern Asia, Europe and Africa. More 
such details are visible in maps of relative 
amounts or the atmospheric transmittance (b). 
Intercomparisons between simultaneous and colocated 
ground based measurements are summarized in Fig. 
4.3 to 4.5. Comparison were possible with data of 
187 pyranometers in the Meteosat sector and 40 
pyranometers in the GMS sector. The rms differences 
are about 6 7. for monthly averages and about 15 7. 
for individual daily sums. The intercomparison in 
Australia (Fig.4.4) show much better results. 
During July 1983 Australia was nearly cloudfree. 
Obviously the determination of the atmospheric 
transmittance is in the presence of clouds more 
uncertain.