Transcript Meteorologisches Observatorium Lindenberg A COMPARISON OF SCAPP RADIATION DATA WITH GLOBAL, DIFFUSE AND DIRECT RADIATION AS WELL SUNSHINE DURATION Klaus Behrens and Rolf-Dieter Grewe German.

Meteorologisches Observatorium Lindenberg
A COMPARISON OF SCAPP RADIATION DATA
WITH GLOBAL, DIFFUSE AND DIRECT RADIATION
AS WELL SUNSHINE DURATION
Klaus Behrens and Rolf-Dieter Grewe
German Weather Service
Meteorological Observatory Lindenberg
[email protected]
[email protected]
TECO, Bucharest, 04.-07.05.2005
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Outline
• Introduction
• The Scanning Pyrheliometer/Pyranometer
• Technical Description
• Calibration
• Comparisons of SCAPP with pyrheliometer and pyranometer data
• hourly means
• daily totals
• Conclusions
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• about 30 manned stations
• two ventilated and heated CM11
measuring global and diffuse
solar radiation
• sunshine duration is measured
by a SONIe
• rising requests from several users
for a higher spatial resolution
• to extend the radiation network at a
stable number of manned is only
possible with an instrument allowing
an automatic (unmanned) operation
l Global radiation
 Global and diffuse solar radiation
uAtmospheric downward radiation
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Radiation Network of the
German Weather Service
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• Bergholter and Dehne (1992) showed the
possibility to measure global, diffuse and direct
solar radiation with one instrument the so called
SCAnning Pyrheliometer/Pyranaometer (SCAPP)
• in future the radiation network of the German
Weather Service will consist of about 30 manned
stations using pyranometers (basic network) and
an extending one of about 130 automatic
(unmanned) stations applying the SCAPP
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Head and sensor
module of the SCAPP
consist of a spherical
sector diaphragm (1), a
diffuser (2), a beamguide (3), two filter slides
KG4 (4a), BG34 (4b)
glass and a
photodetector (5).
weight: 5 kg
height: 260 mm
diameter: 185 mm
The SCAPP as it is used for
measuring direct, diffuse and
global solar radiation as well as
sunshine duration.
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data transmission via
RS232 or RS422/485
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• SCAPP calibration has to be made
outside using the Sun as source
• direct and diffuse solar radiation have
to be measured in parallel with the
registration of the voltage of the SCAPP
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Signal of the direct beam
Signal (a)
Signal (b)
Signal
• SCAPP needs more than one factor
for the correct calculation of the different
radiation quantities
• a basic sensitivity of diffuse radiation
• diffuse radiation inside the SCAPP
depends on direct radiation
• a correction factor for the diffuse
radiation is necessary
• a sensitivity of the direct radiation has
to be determined
Signal of the sky
Signal of the sky
Time
Schematic courses of the SCAPP signal
during one rotation of the head describing
different conditions (a) and (b).
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Reference instruments:
• CH1 960129
• CM22 020073
• CM22 020074
Radiation platform at the
Meteorological Observatory
Lindenberg with the reference
instruments from the BSRN
station for the comparison with
the SCAPP.
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The SCAPP at the
radiation platform
during the
comparison.
• voltages were recorded by
a COMBILOG data logger
and then converted into
irradiances
• SCAPP data were
converted by its own
microprocessor
• all data stored as 1 minute
means
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a)
Global Radiation, March
Diffuse Solar Radiation, March
700
y = 0.9516x - 1.4715
R2 = 0.9991
500
Dsca (W/m²)
Gsca (W/m²)
600
400
300
200
Gsca
Linear (Gsca)
100
0
0
100
200
300
400
500
600
700
Gref (W/m²)
Direct Solar Radiation, March
c)
Isca (W/m²)
1000
y = 0.9611x - 2.0443
R2 = 0.9908
800
600
400
Isca
Linear (Isca)
200
0
0
200
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400
600
Iref (W/m²)
800
1000
400
350
300
250
200
150
100
50
0
b)
y = 0.9398x - 0.8387
R2 = 0.9983
Dsca
Linear (Dsca)
0
100
200
Dref (W/m²)
300
400
Fig. a-c: Scatter diagrams of hourly means
of global (G), diffuse (D) and direct solar
radiation (I) measured by the SCAPP (sca)
and pyranometers as well as a
pyrheliometer as reference instruments
(ref) and the corresponding regression
lines in March, respectively. Furthermore,
in the text boxes the regression
coefficients and the coefficient of
determination (R²) are given.
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Diffuse Solar Radiation, July
Global Radiation, July
y = 1.0288x - 4.0348
R2 = 0.9989
800
600
400
GS
Linear (GS)
200
0
0
200
400
600
Gref (W/m²)
800
1000
Direct Solar Radiation, July
1000
y = 1.0272x - 2.4586
R2 = 0.9951
Isca (W/m²)
800
600
400
IS
Linear (IS)
200
0
0
200
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400
600
Iref (W/m²)
800
500
450
400
350
300
250
200
150
100
50
0
y = 1.0091x - 0.3897
R2 = 0.9989
Dsca (W/m²)
Gsca (W/m²)
1000
1000
DS
Linear (DS)
0
100
200
300
Dref (W/m²)
400
500
Fig. a-c: Scatter diagrams of hourly means
of global (G), diffuse (D) and direct solar
radiation (I) measured by the SCAPP (sca)
and pyranometers as well as a
pyrheliometer as reference instruments
(ref) and the corresponding regression
lines in July, respectively. Furthermore, in
the text boxes the regression coefficients
and the coefficient of determination (R²)
are given.
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Global Radiation, December
250
Gsca (W/m²)
Dsca (W/m²)
y = 0.9706x - 1.0241
R2 = 0.9956
200
150
100
Gsca
Linear (Gsca)
50
0
0
50
100
150
Gref (W/m²)
200
250
c)
Direct Solar Radiation, December
700
600
y = 0.9664x - 1.7518
R2 = 0.9644
Isca (W/m²)
500
400
300
200
Isca
Linear (Isca)
100
0
0
100
200
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300
400
Iref (W/m²)
500
600
700
b)
Diffuse Solar Radiation, December
a)
140
120
100
80
60
40
20
0
y = 0.9414x - 0.5673
R2 = 0.9967
Dsca
Linear (Dsca)
0
20
40
60
80
Dref (W/m²)
100
120
140
Fig. a-c: Scatter diagrams of hourly means
of global (G), diffuse (D) and direct solar
radiation (I) measured by the SCAPP (sca)
and pyranometers as well as a
pyrheliometer as reference instruments
(ref) and the corresponding regression
lines in December, respectively.
Furthermore, in the text boxes the
regression coefficients and the coefficient
of determination (R²) are given.
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Regression constants (m: slope coefficient; c: point of intersection with the y-axis) and the
coefficients of determination (R²) of the hourly means of the SCAPP and the corresponding
reference instruments for global, diffuse and direct solar radiation
Month
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
m
0.931
0.945
0.952
0.974
0.995
1.011
1.029
1.021
1.013
0.989
0.976
0.971
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global
c
-0.812
-1.043
-1.472
-2.658
-2.388
-2.364
-4.035
-3.344
-2.450
-1.355
-1.002
-1.024
R²
0.997
0.999
0.999
0.998
0.998
0.999
0.999
0.999
0.999
0.999
0.998
0.996
m
0.920
0.933
0.940
0.951
0.984
1.012
1.009
1.002
0.995
0.979
0.979
0.941
diffus
c
-0.584
-0.679
-0.839
-0.700
-1.347
-1.807
-0.390
-0.548
-0.331
-0.615
-0.735
-0.567
R²
0.998
0.999
0.998
0.998
0.999
0.999
0.999
0.999
0.998
0.999
0.998
0.997
m
0.932
0.956
0.961
0.989
1.028
1.032
1.027
1.026
1.006
0.986
0.985
0.966
direct
c
-2.189
-1.629
-2.044
-4.542
-0.382
-2.108
-2.459
-3.923
-5.241
-2.929
-1.051
-1.752
R²
0.960
0.983
0.991
0.992
0.977
0.994
0.995
0.996
0.992
0.982
0.970
0.964
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1.2
1.0
Gsca/Gref
0.8
0.6
Gsca/Gref (Jul)
Gsca/Gref (Dec)
0.4
0.2
0.0
0
200
400
600
Gref (W/m²)
800
1000
Hourly ratios Gsca/Gref in dependence on Gref for July and December.
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Gsca/Gref; Dsca/Dref
1.1
J
F
M
A M
J
J
A
S
O
N
D
1.0
0.9
0.8
Gsca/Gref
Dsc/Dref
new calibration constants
0.7
0.6
Annual courses for the daily ratios Gsca/Gref and Dsca/Dref.
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Conclusions:
• The comparison showed that the measurements of the SCAPP in most cases are
in good agreement with the results of the reference instruments.
• At lower global radiation (about <75 W/m²) the SCAPP results are frequently to
low in comparison with the reference. In future this will be improved.
• The SCAPP is a multisensor of „Moderate quality“, which is suitable for radiation
measurements where highest quality is not demanded.
Thank you for your attention!
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