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Comments on Calculation of monthly average global solar radiation on horizontal surfaces using daily hours of bright sunshine
Solar Energy, Vol. 54, No. 2, p. 137, 1995 Copyright 0 1995 Elsevier Science Ltd F’rinted in the USA. All rights reserved 0038-092X/95 $9.50 + .OO
Pergamon 003&092X( 94)ooo96-4
LETTER
TO THE EDITOR
Comments on Calculation of Monthly Average Global Solar Radiation on Horizontal Su$aces Using Daily Hours of Bright Sunshine
N. HALOUANI, C. T. NGUYEN, and D. VO-NGGC Solar Energy 50,247-258 ( 1993) To the Editor:
Author’s reply . . .
I wish to draw attention to several errors/inconsistencies which appeared in the article mentioned above. The authors reported that the underestimation of global solar radiation was drastically pronounced using Rietveld’s model for many of the considered stations, with observed MBE values as large as 33.3% (Coral Harbour station in the Northern Region ) . This statement is inconsistent as the MBE is positive for the Coral Ha&our station, which indicates that for this particular station the model grossly overestimated global solar radiation. Furthermore, Table 2 indicates that for the Coral Harbour station, the MBE and RMSE values are 33.3% and 24.1%, respectively. This is obviously incorrect as it can easily be shown that the variance, a2, is given by (RMSE2 - MBE2). Since u* r 0 then RMSE2 r MBE2. A similar error also occurs in the computation of MBE and RMSE for the Hay’s model at the Churchill A station in the Praires where the MBE and RMSE are reported to be - 11.O% and 8.8%, respectively.
There were unfortunately some mistakes in the computed values of RMS and Mean Bias errors for two of the 46 stations studied, namely the Coral Harbour Station and the Churchill A Station. Also the Coral Harbour Station should not have been used as an example in the sentence relating to the severe underprediction of Rietveld’s model; such underprediction is, however, still true for 10 of the 12 Northern Region stations. The authors wish to apologize for the above errors and inconsistence. We do believe, however, that because of the large number of stations considered, the paper’s general conclusions on the performance of the different models still hold true. C. T. Nguyen Universite de Moncton School of Engineering Moncton, New Brunswick ElA 3E9 CANADA
R. J. Stone Department of Crop Science University of the West Indies, St. Augustine Trinidad, WEST INDIES
137
Pergamon 003&092X( 94)ooo96-4
LETTER
TO THE EDITOR
Comments on Calculation of Monthly Average Global Solar Radiation on Horizontal Su$aces Using Daily Hours of Bright Sunshine
N. HALOUANI, C. T. NGUYEN, and D. VO-NGGC Solar Energy 50,247-258 ( 1993) To the Editor:
Author’s reply . . .
I wish to draw attention to several errors/inconsistencies which appeared in the article mentioned above. The authors reported that the underestimation of global solar radiation was drastically pronounced using Rietveld’s model for many of the considered stations, with observed MBE values as large as 33.3% (Coral Harbour station in the Northern Region ) . This statement is inconsistent as the MBE is positive for the Coral Ha&our station, which indicates that for this particular station the model grossly overestimated global solar radiation. Furthermore, Table 2 indicates that for the Coral Harbour station, the MBE and RMSE values are 33.3% and 24.1%, respectively. This is obviously incorrect as it can easily be shown that the variance, a2, is given by (RMSE2 - MBE2). Since u* r 0 then RMSE2 r MBE2. A similar error also occurs in the computation of MBE and RMSE for the Hay’s model at the Churchill A station in the Praires where the MBE and RMSE are reported to be - 11.O% and 8.8%, respectively.
There were unfortunately some mistakes in the computed values of RMS and Mean Bias errors for two of the 46 stations studied, namely the Coral Harbour Station and the Churchill A Station. Also the Coral Harbour Station should not have been used as an example in the sentence relating to the severe underprediction of Rietveld’s model; such underprediction is, however, still true for 10 of the 12 Northern Region stations. The authors wish to apologize for the above errors and inconsistence. We do believe, however, that because of the large number of stations considered, the paper’s general conclusions on the performance of the different models still hold true. C. T. Nguyen Universite de Moncton School of Engineering Moncton, New Brunswick ElA 3E9 CANADA
R. J. Stone Department of Crop Science University of the West Indies, St. Augustine Trinidad, WEST INDIES
137