INFLUENCE OF SKY CONDITIONS ON ESTIMATION OF PHOTOSYNTHETIC PHOTON FLUX DENSITY FOR AGRICULTURAL ECOSYSTEM

International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences

Yoshimura, M.^2¹  Yamashita, M.^1² 

[1] PASCO Corporation, PASCO Research Institute, 2-8-10 Higashiyama, Meguro-ku, Tokyo, Japan^2;Tokyo University of Agriculture and Technology, Faculty of Agriculture, 3-5-8 Saiwai-cho, Fuchu, Tokyo, Japan^1

关键词: PPFD;    PAR;    Solar radiation;    PAR fraction;    Quantum-to-energy ratio;    Diffuse ratio;    Clearness index;    Sky conditions;   

DOI  :  10.5194/isprs-archives-XLII-3-2041-2018

学科分类：地球科学(综合)

来源: Copernicus Publications

【 摘 要 】

Photosynthetic photon flux density (PPFD: µmol m⁻² s⁻¹) is indispensable for plant physiology processes in photosynthesis. However, PPFD is seldom measured, so that PPFD has been estimated by using solar radiation (SR: W m⁻²) measured in world wide. In method using SR, there are two steps: first to estimate photosynthetically active radiation (PAR: W m⁻²) by the fraction of PAR to SR (PF) and second: to convert PAR to PPFD using the ratio of quanta to energy (Q / E: µmol J⁻¹). PF and Q/E usually have been used as the constant values, however, recent studies point out that PF and Q / E would not be constants under various sky conditions. In this study, we use the numeric data of sky-conditions factors such cloud cover, sun appearance/hiding and relative sky brightness derived from whole-sky image processing and examine the influences of sky-conditions factors on PF and Q / E of global and diffuse PAR. Furthermore, we discuss our results by comparing with the existing methods.

【 授权许可】

CC BY