Quality assessment of CAMS radiation service values against 11 INPE stations

Last update: Jan. 2016

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Protocol

Date & Authors: Jan. 2016

  • Dr Etienne Wey, Transvalor
  • Pr Lucien Wald, MINES ParisTech
  • Dr Philippe Blanc, MINES ParisTech
  • and Dr Claire Thomas, Transvalor

(A publication is on the way)

The CAMS radiation service values are compared to the 1 minute Global Horizontal Irradiation measurements from the 11 stations of the INPE network.
The measurements, also named observations, were originally quality checked using the procedure described here. As only the GHI component is available in the observations for both datasets, no consistency check is possible via cross-comparison from one component to another. Unfortunately, this protocol turned out to be insufficient for these hourly measurements and that the test to discard the not plausible values ("Extremely Rare Limits" and "Physical Possible Limits") were too permissive; Too many outlyers remained after the QC. Prior the computation of the different quantities to assess the deviation between the satellite estimates and the station measurements as depicted in the protocol of validation, we decided to discard also the measurement values when they are:

  • below 2% * clear sky dry, which corresponds to the ESRA clear sky with no turbidity
  • above 120% * clear sky dry
  • time shift in the data was also observed for several days in the time series. We decided that if more than 10% of the values were located during nightime, the whole day is discarded.

We remind that the other steps are:

  • Set night, sunrise and sunset observation values to zero
  • As soon as the quality check procedure is over, then aggregate the 1 min values to generate the hourly values if at least 85% of the 1-min slots are available. Apply an intelligent mean which takes into account the sun position at each minute.
  • Then the hourly values are aggregated to generate partial daily and monthly sums as depicted in the protocol of validation.

Illustration: list of the INMET and INPE stations used for the validation

List of the 11 stations

Station State Latitude Longitude Altitude (m) Period
CachoeiraPaulista RJ -22.690 -45.006 574 2014-03-01 to 2015-01-31
CampoGrande MS -20.438 -54.538 677 2012-09-01 to 2015-01-31
Chapeco SC -27.080 -52.614 700 2009-01-01 to 2009-12-31
Cuiaba MT -15.555 -56.070 185 2006-01-01 to 2012-12-31
Curitiba PR -25.495 -49.331 891 2014-09-01 to 2015-01-31
Natal RN -5.837 -35.206 58 2009-01-01 to 2015-01-31
Ourinhos SP -22.949 -49.894 446 2006-02-01 to 2011-03-31
Palmas TO -10.178 -48.362 216 2005-04-01 to 2014-06-30
Petrolina PE -9.069 -40.320 387 2007-01-01 to 2014-06-30
Saoluiz MA -2.594 -44.212 40 2009-01-01 to 2014-06-30
Sombrio SC -29.096 -49.813 15 2013-01-01 to 2015-01-31

Quality assessment results of GHI values

CAMS radiation service -- GHI Quality assessment results vs. the INPE stations in Brazil
MONTHLY SUM OF HOURLY IRRADIATION
Station Number of values Mean
- INMET station -
(kWh/m²)
Bias
(kWh/m2)
(relative in %
)
RMSE
(kWh/m2)
(relative in %
)
Correl. coeff.
CachoeiraPaulista 11 148.6 8.6 (5.8%) 9.0 (6.1%) 0.997
CampoGrande 16 146.2 8.8 (6.0%) 10.5 (7.2%) 0.974
Chapeco 12 130.7 6.5 (4.9%) 8.5 (6.5%) 0.998
Cuiaba 79 147.2 9.4 (6.4%) 10.5 (7.2%) 0.958
Curitiba 4 159.1 7.1 (4.4%) 7.6 (4.7%) 0.991
Natal 47 177.4 9.2 (5.2%) 10.2 (5.8%) 0.988
Ourinhos 58 135.3 11.8 (8.7%) 13.1 (9.7%) 0.970
Palmas 63 142.1 3.6 (2.5%) 9.3 (6.6%) 0.963
Petrolina 82 155.8 20.4 (13.1%) 21.0 (13.5%) 0.990
Saoluiz 46 141.7 28.2 (19.9%) 29.2 (20.6%) 0.986
Sombrio 23 119.5 19.1 (16.0%) 22.2 (18.6%) 0.989

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CAMS radiation service -- GHI Quality assessment results vs. the INPE stations in Brazil
DAILY SUM OF HOURLY IRRADIATION
Station Number of values Mean
- INMET station -
(Wh/m²)
Bias
(Wh/m2)
(relative in %
)
RMSE
(Wh/m2)
(relative in %
)
Correl. coeff.
CachoeiraPaulista 315 5187.6 299.0 (5.8%) 526.7 (10.2%) 0.972
CampoGrande 447 5339.4 315.7 (5.9%) 660.5 (12.4%) 0.935
Chapeco 331 4728.9 230.5 (4.9%) 574.7 (12.2%) 0.970
Cuiaba 2348 5075.9 323.3 (6.4%) 719.1 (14.2%) 0.884
Curitiba 118 5461.8 255.9 (4.7%) 665.1 (12.2%) 0.946
Natal 1394 6082.4 317.0 (5.2%) 579.4 (9.5%) 0.932
Ourinhos 1635 4914.5 429.6 (8.7%) 731.4 (14.9%) 0.937
Palmas 1770 5320.9 141.5 (2.7%) 815.6 (15.3%) 0.799
Petrolina 2435 5412.2 712.0 (13.2%) 840.9 (15.5%) 0.949
Saoluiz 1324 4926.5 980.8 (19.9%) 1188.4 (24.1%) 0.842
Sombrio 646 4332.4 688.6 (15.9%) 933.6 (21.5%) 0.961

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CAMS radiation service -- GHI Quality assessment results vs. the INPE stations in Brazil
HOURLY SUM OF HOURLY IRRADIATION
Station Number of values Mean
- INMET station -
(Wh/m²)
Bias
(Wh/m2)
(relative in %
)
RMSE
(Wh/m2)
(relative in %
)
Correl. coeff.
CachoeiraPaulista 3659 446.6 25.7 (5.8%) 89.3 (20.0%) 0.962
CampoGrande 5268 453.1 26.8 (5.9%) 116.1 (25.6%) 0.930
Chapeco 3855 406.8 20.1 (4.9%) 98.8 (24.3%) 0.948
Cuiaba 27502 433.6 27.6 (6.4%) 113.3 (26.1%) 0.930
Curitiba 1500 429.7 20.1 (4.7%) 129.3 (30.1%) 0.919
Natal 16311 519.8 27.1 (5.2%) 87.4 (16.8%) 0.966
Ourinhos 19047 421.9 36.9 (8.7%) 103.0 (24.4%) 0.947
Palmas 20756 454.1 12.1 (2.7%) 136.3 (30.0%) 0.894
Petrolina 28670 459.7 60.5 (13.2%) 106.2 (23.1%) 0.964
Saoluiz 15722 414.9 82.6 (19.9%) 154.6 (37.3%) 0.911
Sombrio 7579 369.3 58.7 (15.9%) 122.5 (33.2%) 0.935

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