Discrete Ordinate Method for the Estimation of Downward Solar Flux in Penang, Malaysia

• Published in: IOP Conference Series: Earth and Environmental Science
• Main Authors: Yusuf, H, Tahrin, N Mohamed, Lim, H.S
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: IOP Publishing 2020
• Subjects: Aerosol Robotic Network
• Online Access: http://dx.doi.org/10.1088/1755-1315/489/1/012032; https://iopscience.iop.org/article/10.1088/1755-1315/489/1/012032/pdf; https://iopscience.iop.org/article/10.1088/1755-1315/489/1/012032

Abstract Downward shortwave solar energy is a very important parameter for the surface energy balance, which affects human life and other activities of the ecosystem. It is also one of the critical terms in the study of climate change that requires consistent contributions from different researchers. In this paper, we proposed the use of Discrete Ordinate Radiative Transfer method (DISORT) to estimate the downward Total Solar Flux (TSF) in Penang, Malaysia. The measured aerosols optical properties obtained from the ground-based Aerosol Robotic Network (AERONET) data were used as inputs to the DISORT codes. Data of the pyranometer ground-based measurements of TSF were also used for validation of the simulated results from this study. The results for two days, 17 January 2015 and 1 February 2015, have been used to test the performance and accuracy of the method. It is found that there is good agreement between the results from this study and the ground-based measurement results available from AERONET. The validation results show that for the first day (r = 0.9968), (R 2 = 0.9936), root-mean-square error (RMSE) of 36.66 and mean absolute percentage error (MAPE) is 16%. For the second day (r = 0.9986), (R 2 = 0.9971), (RMSE = 33.06), (MAPE = 12%). The small variation between the two results was due to error that might have arisen because of the model imperfection, and from the small inefficiency of the pyranometer and sunphotometer. Nevertheless, this study shows that the proposed integration of ground-based and model simulation is an excellent and a valid alternative, for the estimates of solar radiation and the study of the impact of aerosols on the TSF everywhere and at all times, particularly when the results from other sources are not available.