309
HOOELLERCEBNIS
Pyranometer
of global
= AL = 57.
KWHM
-2
PYRANOHETERHESSUNG IN KWHM
(PYRANOMETER MEASUREMENT)
= 5.57 kWh/m 3 = 2005 J/cm 2
Fig. 4.3: Intercomparison between ground-based
measurements and model results
satellite: lieteosat time: June 1983
here: monthly means of the daily sums
: mean daily sum, a: mean error (rms)
Pyranometer
measurements
= 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.
