[H-TT18] Environmental Remote Sensing

[HTT18-P05] Accounting for atmospheric factors to estimate photosynthetically active radiation from surface solar irradiance

*YAJIE DAI¹, Hitoshi Irie¹, Alessandro Damiani¹ (1.chiba university)

Keywords:Photosynthetically active radiation, the ratio of PAR to surface solar irradiance, atmospheric factors, identification of weather conditions

Photosynthetically active radiation (PAR) is the energy source for organic matter production in plants. To analyze the long-term PAR changes where no proper PAR data are available, it has been proposed to build the long-term PAR data set using the ratio of PAR to surface solar irradiance (SSI) (PAR/SSI). However, the PAR/SSI is affected by local atmospheric factors. Particularly, the identification of weather conditions is necessary to estimate PAR, but accurate cloud segmentation is challenging. We propose a simple methodology to distinguish clear sky, overcast, and partial cloudy conditions. We exploited the broad range of meteorological instruments available at the SKYNET super site of Chiba University (Japan) to develop a reconstruction method accounting for the atmospheric factors more accurately than previous methods based on annual or monthly averages of PAR/SSI. Using high-temporal-resolution data, we optimized our PAR estimation under clear sky, overcast, and partial cloud conditions. Then, we achieved that the average deviation of the estimated PAR from the quantum sensor PAR-01D is less than 10% when the solar zenith angle is small. This study is expected to make more PAR data available, providing a basis for understanding the impact of microclimate changes on plant photosynthesis.