Journal of the Korean Solar Energy Society ISSN:1598-6411(Print) 2508-3562(Online) 한국태양에너지학회 논문집

Photosynthetically active radiation (PAR; wavelength 400 ~ 700 nm) is the spectral range of solar radiation used by plants for photosynthesis. PAR data are used in various fields of research, such as that focusing on surface vegetation growth, the light energy–chemical energy conversion process, and the terrestrial carbon cycle. In this study, we analyze the variability between Global Horizontal Irradiance (GHI) and PAR according to the solar zenith angle, the clearness index, using GHI and PAR observations from 2016 to 2020 at Anmyeondo Flux Tower of Korea Forest Research Institute (KFRI). We confirm that the PAR decreases and the variability of the ratio of PAR to GHI increases as the atmospheric optical path increases. We also confirmed that the PAR increased and the ratio of PAR and GHI decreased as the clearness index increased. Using the results of these relationships and prior studies, we develop and evaluate empirical models that estimate PAR from GHI. The R² representing the estimation accuracy of the model was 0.988 to 0.996, indicating very high accuracy. With these results, the observation data from the KFRI’s Wando, Pyeongchang, and Samcheok Flux Towers during the same period showed that R² was very high at 0.977 ~ 0.988, confirming its transferability in other regions. Despite the high R², the Mean Bias Error (MBE) for each site was shown to be different. To solve this problem, a model with relative humidity and temperature was developed to apply regional conditions for each site, and showed similar R² to prior models with less MBE. It is expected that the results of this study will be used as policy references such as attracting solar power complexes by drawing up a seasonal map of the Korean peninsula of PAR with solar radiation data observed at the Korea Meteorological Administration's Automated Synoptic Observing System (ASOS).